Social class Essay Example for Free

Social class Essay Social class indeed does make a distinction in the lives and future lives of American children. In his works, Lareau draws on a comprehensive and carefully observations of white and black middle-class and working and poor families offering a dramatic portrait of childhood in the modern world. The social class that a child finds him/her in decides whether he/she will achieve the desirable American vision. Parenting and childhood differ with social class; a social class discrepancy influences the speed and rhythm of daily life. The social class in which the parent belongs to impact significantly on the way the parent will bring up his/her children. Social class creates a unique parenting style. Parents differ by class in the way they describe their own task in their children’s lives as well as how they understand the environment of upbringing. The middle class parents tend to conform to a cultural logic of childbearing which we call concerted cultivation. They attempt to promote their children’s talents by use of planned free time activities and general reasoning. They also support their children to get involved in various age-specific planned activities that govern family life and generate huge labor, especially for mothers. The parents portray these activities as a way of conveying essential life skills to their children (Lareau 20). Middle class parents lay emphasis on the use of language and development of reasoning and use of conversation as they favored form of discipline. Middle class parents discuss with their children at length seeking their opinions and encouraging their ideas. Their strategy involves direct expenses like the cost of buying equipment for plating with their children and indirect expenses for example the expenses involved in taking off leave to spend with their children. They get involved in sports, music and educational activities. This kind of nurturing creates diversity of experiences for children and generates an anxious pace for parents, leads to individualism amidst the family and emphasizes on children’s performance. Working class and poor parents engage in a cultural logic of achievement of natural growth, providing the conditions under which children can develop while leaving the children free to select the kind of activities to engage in during their free time. The childrearing approaches for employed class and unemployed emphasize on the importance of natural growth. These parents believe their children will grow and succeed provided they are given food, love and safety. They do not center on building up their children’s particular talents (Lareau 32). Working parents make use orders rather than logic. There is no much talking in lives of employed parents. Parents to children discussion in working class is so minimal.. Parents tend to use stiff commands and expect quick positive answers. Children who disobey parent’s orders expect to be punished. Working parents are inclined to issue more orders to their children and put more stress on physical discipline as compared to middle class parents. Working–class children engage in few planned play activities as compared to children whose parents are in the middle class. Working parents do not monitor their children’s free time and activities; they only intervene in specific areas such as dressing, meal times and chores They also have more free time and hence more profound and stronger ties with their extended families (Hart and Todd 19). On the other side children in middle class have weaker social ties due to the fact that they get engaged in adult-organized activities. The busy and strict children’s schedules found among middle class families make it hard to arrange and attend regular extended family get together. Their parents also tend to form weak rather than strong ties by having social networks that include professionals only. Working parents not likely to include professionals in their social networks but are more likely to speak with their kin on a daily routine than their friend. Their children interact with different age groups which include their cousins and children in their neighborhood. Despites differences in values between the two classes, there are disparities amongst parents and children behavior. A difference in cultural logic gives parents and their children differential resources in their interactions with professionals and other adults away from home. Working parents are more skeptical to professionals such as doctors and teachers than middle class guardians. They also display fear of the powerful individuals in the society as opposed to their counterpart. Middle class parents are better armed to exercise power over other teanagers compared to working parents (Lareau 41). Working class parents teach their children to keep themselves away from those occupying high places in the society, to be distrustful of institutions and to some extend to oppose official authority. These make the children to absorb the adult’s feeling of subjection in their society relationships (Hochschild 17). The middle class children enjoy fortunate lives; they live in large houses, some have swimming pool, most children have their own bedrooms with some with computers and varied kinds of toys. They also tend to enjoy their holidays as they flew out of the country in airplanes and travel by sports car one or two hours from home to participate in their activities (Hofferth and John 33). The employed class children display a sense of restraint in their relations with powerful figures in society. They are not likely to try to tailor interactions to favor their own choices. They blindly conform to accept actions of persons in authority. Employed parents appear not to be aware of their children’s school circumstances for example when they children are not doing assignments. They believe that the academic issues should be handled only by the teachers. Due to fear of intimidation by authority figures, they fear teaching their children the wrong things. They perceive school and home as separate worlds. They also dismiss school rules as irrational. Middle-class working parents consider themselves equal or at times superior to their children teachers. They walk in and out of classrooms comfortably as though they have the right and freely ask for their children to be included in certain school programs and more specifically try to modify the school experience to favor their children. The fact that school use specific linguistic structure, authority models and form of syllabus which the children from middle/upper children are familiar with gives them a ‘home advantage’. School official themselves acknowledge the use of concerted cultivation being members of the middle-class themselves; they believe that concerted cultivation is the right way to bring up children. Lareau never praise one parenting style as opposed to the other. Both taking care of children have their own demerits and merits. For example, Middle class children are only taught the rules superseding relations with official figures but are not taught on important social skills such as planning their free time hours during weekends or holidays or even on how to associate with adults in a subordinate manner. Middle class children have also learned from their parents to make things work in their own advantage at the expense of others. For example, they make special request to teachers to change time-tables to house their desires (Lareau 47). Each strategy of childrearing makes sense in its own setting. All these disparities in parenting style have some long term consequences. It has been observed that the approaches utilized by parents and children are not uniformly successful across classes. However, our society emphasizes on the importance of skills learned from the concerted cultivation than those learned through the achievement of natural growth. When working-class children move from childhood to adulthood, they find that the ability to be organized and to be eloquent are appreciated more than the skills to operate outside formal organization, placing them at a lesser competitive advantage. Parent’s economic resources play a major role in determining the kind of parenting style the parent adapts. Middle-class parents are advantaged to have access to resources as opposed to their counterparts. For example the middle class parents sees the enrollment fees charged in school as small while for the working class it is really expensive. Middle class parents are able to pay for expensive clothes for their children, buy them equipment to play with, pay for their hotel accommodations when far from home during vacations, afford to buy them fast food and summer camps. Middle-class parents have dependable private means of transportation and flexible working schedules which enable them to spend more time with their children. Educational resources also play an important role in parenting styles. Middle class high level of education gave them an upper hand when it comes to facilitating concerted cultivation and especially in institutional involvement. This also bestow in them assurance of criticizing educational professionals and prevailing in school issues. Where as employed parents view teachers as their social superiors. Works Cited Hart, B. and Todd, R.Significant Disparities in the Daily Practices of Young Children. Baltimore: Paul H. Brookes, 1996. Hochschild, J. Looking Into the American Reality: Race, Class and the Spirit of the Country. Princeton: Princeton University Press, 1995. Hofferth, S. and John, S. â€Å"How American Family Use Their Free Time†. Journal of Marriage and the Family Relations 63(4), 2001. 295-308 Lareau, Annette. Invisible Disparity: Social Class and Child nurturing in Black Families and White Families. American Sociological Evaluation, 67(2002): 747-776. Lareau, Annette. Unequal Upbringing: Class, Race, and Family Life. Berkeley: California Press, 2003.

Aluminium Wings Verses Composite And Future Wing Materials Engineering Essay

Aluminium Wings Verses Composite And Future Wing Materials Engineering Essay The comparison of the properties of the materials used in aluminium and composite wings and the advantages and disadvantages of which they both possess and make them suitable for use within the manufacture of wings. A discussion of future materials which have been developed and are suitable for the use in wings will also take place. Collected information came from appropriate websites and books. Aluminium is the widest used material for the manufacture of aircraft wings to date since the first time it was used in the 1920s. Now the use of composites is becoming greater utilized in the manufacturing of aircraft wings at present instead of traditional aluminium wings. This is mainly to do with the weight saving properties that composites can posse. Weight saving properties is just one of the advantages of composite materials, another can be stiffness, but there are also disadvantages to using composites compared to aluminium, such as if they get damaged they need replacing immediately unlike aluminium which is very tolerant to damage. Aluminium production and repair is also much easier than that of composites. Aluminium and composites both have their own advantages and disadvantages and their properties have to be taken into account before any material changes are made. Future developments will hopefully provide a material that which will provide sufficient advantages and mini mal disadvantages compared over composites or aluminium. This report will look at the Boeing 737, which features aluminium wings, and the Boeing 787 dreamliner, which incorporates composite wings, and refer to them for the comparison of the different properties and structures of the two wing types. It will look at each type of material found in a traditional aluminium aircraft wing structure at present and will go into depth about the use of composites in wings instead of aluminium at present and in the future. The types of composites used, as well as investigating whether the structure of the wing had to be altered to compensate for the different properties of the composites will be discussed. The strength and weight properties of each different type of aluminium and composites used in an aircraft wing will also be examined. Types of corrosion which occur on an aluminium wing, including the inspection and repair of it will also be included, as well as the inspection and repair of composite materials and the types of damage which can occur in composites, such as delamination. The cost of production and repair of composites compared to aluminium and aluminium alloys, as well as the weight saved resulting in lower running costs for the company will be examined. The collected information will then be compared and advantages and disadvantages of each type of wing will be produced. It will also look at future aircraft wing materials, such as the use of incorporating aluminium with composites, and if they will change the way aircraft looks at present. The different properties of the new materials will also be examined and compare to the properties of both aluminium and composite wings. An overall conclusion of all the main findings and collected information will also be given. Recommendations will also be given at this point. Methodology After deciding what the topic of the report was going to be about, the research undertaken would need to be relevant. The first part of the study was to find information about Aluminium wings and the materials and structures which made them. This part incorporated finding and recording relevant information from certain websites off the internet. Another source used was finding appropriate books which gave suitable information about the subject in hand. Finding information on composite materials and structures was carried out by the same method. Locating appropriate information about future aircraft wing materials was carried out only with the use of the internet. Findings Aluminium wings Types Aluminium (Al) has been used in aircraft since the 1920s due to it being lightweight while also being relatively strong. It is used over steel as aluminium is three times the density less then that off steel, this means that for the same density the aluminium would be three times thicker, resulting in it being much stronger. Aluminium is also has good corrosion resistance, which is an advantage as an aircraft is subject to all weather conditions. Nowadays aluminium is joined with other elements to change the properties of the metal, improving specific areas of it, creating an aluminium alloy. At the present time, Aluminium alloys make up a vast total of a commercial aircrafts unloaded weight. Alloys Adding different elements to aluminium improve different properties, for example adding zinc to aluminium will improve the strength of the material. The added zinc allows the aluminium to be heat treated, where the metal is heated and cooled which in turn changes the structure of the metal along with its properties. More than one element can be added at the same time resulting in different properties being produced from having the same main alloying element. Even tho some of the properties of the aluminium will improve, the alloying elements need to be correctly chosen as other properties within the metal will be sacrificed. Certain aluminium alloys are used in the manufacturing of aircraft wings, the types of aluminium alloys, along with where it is used, the elements which are used to create the alloy and the improved properties are listed in the table below. Al Alloy Area Used Elements (%) Properties 7178 Spars, Beams, upper wing skin Zinc, magnesium, copper High compressive strength to weight ratio 7055 Lower wing skin Zinc, magnesium, copper Improved stress corrosion and fatigue resistance 7075 Wing ribs zinc Improved stress corrosion cracking resistance, high mechanical properties 2024 Slats, flaps copper Good fatigue performance, fracture toughness, slow propagation rate The Boeing 777 also uses the aluminium alloy 7055 due to it having a greater compressive strength than other alloys that had been tried before. Due to this, it was able to be used in the manufacture of parts of the wing, in the stringers and the upper wing skin. Corrosion Even though Aluminium has good corrosion resistance, it is still susceptible to corrosion. Aluminium is somewhat protected from corrosion as an aluminium oxide film forms on the surface. This is due to the aluminium being protected from additional oxidation by the existing aluminium oxide film. Minimal corrosion, such as light surface or small pitting corrosion, does not normally cause a problem to the metal. Heavier corrosion occurring in metals used on aircraft is not wanted as it can lead to a weakening in the structural rigidity of the metal. If this is not rectified it can lead to a structural failure within part of the aircraft. Corrosion can occur in many different forms, which include pitting, intergranular, and galvanic corrosion. Pitting This is one of the main types of corrosion which occurs on an aircrafts wing. This type of corrosion is a localised type and starts on the surface of a metal, whether it is on the skin panels of the aircraft or within the aircraft itself. It works its way through the surface protection of the metal, and then penetrates its way further into the metal creating a hole within the metal itself. Due to metals have different mechanical and chemical properties, when pitting corrosion occurs, the pits created will be different from one metal to another, as shown in on the right. This hole decreases the strength of the metal due to the grain damage caused by the pitting corrosion.pitting_shape.gif Detection One way of detecting certain corrosion is by using x-rays or gamma rays to take a picture of the piece of metal suspected of having corrosion. Once the picture is developed, it is clear to see where the corrosion, such as pitting, is taking place in the metal, as it produced a darker spot on the film. This is due to less of the radiation being absorbed where the corrosion is taking place. If pitting corrosion is taking place, the image can be used also to establish the depth of the pit within the metal. Another way of determining whether pitting corrosion has occurred on a piece of metal is by the use of Eddy currents. This type of non-destructive testing uses magnetic fields, where the metal object being tested is placed. The magnetic field is produced by putting an alternating current through a coil. An alternation in the back EMF (Electromotive force) occurs when the eddy current gets disturbed by a pit in the metal. This alternation is amplified so it can be seen as an image or heard as a sound by the operator. Prevention There are lots of ways to try and prevent corrosion from occurring. One method is to uses surface treatments which protect the surface of the metal, therefore reducing the chance of corrosion and painting the metal surface can also prevent corrosion as no air or moisture can tough the metal. The use of cathodic protection can also prevent corrosion. Composites The use of composites within aircrafts is a relatively new concept. They were first introduced in the 1980s in secondary aircraft components, such as wing leading and trailing edges, and then as more composites were produced they made their way into larger structures in the 1990s. The Boeing 787 dreamliner tries to make the fullest use out of composite materials that is possible. Around 50% of the full aircraft, including several parts of the wings are manufactured using composites. The rest is manufactured using other materials, such as aluminium, which incorporate properties which at the present cannot be bettered by composites. At the moment composites are used mainly on non structural parts of the wings, and are used on parts such as the wings skins and the flaps. The great attraction for airline industries to use composites within the manufacture of their aircraft is because composites can be strong, and at the same time be lightweight. This means that heavier metals can be replaced with lighter weight composites which have the same strength. This causes the overall weight of the aircraft to decrease, resulting in a more fuel efficient aircraft as less fuel is needed to be burned to move the aircraft. This is an advantage to an airline company as it would result in lower running costs for that aircraft. Costs in manufacturing were also managed to be reduced as during assembly, a smaller quantity of fasteners were needed and there were also a smaller amount of parts required to construct the component. Composites do have disadvantages compared to metals for use within aircraft. One of these is that damage to composites can be difficult to see. Another is due to the fact that composites do not conduct electricity which may cause a problem if the aircraft is struck by lightning. These have also been concerns regarding the safety of the use of composites if there was a crash. Make up Composites are made up by joining together two or more materials which creates a material with improved properties compared to that of both original materials. Composites are made up of a matrix, which is a resin which joins together with a reinforcing material, which is a fibre. There are different types of reinforcing fibre and matrix which individually have different properties and need to be carefully chosen to make sure that they will be suitable for their purpose within the aircraft if chosen. The most commonly used reinforcing fibre used in aircraft is Kevlar. This is due to it having the greatest impact resistance and tensile strength compared to all other reinforcing materials while still being reasonably light. Types Carbon fibre reinforced plastic is the composite used within the manufacture of the Boeing 787 aircraft wing. This composite is used as it has lightweight qualities while also being very strong, and can have the equivalent strength to steel. It is manufactured using carbon fibre as the reinforcing fibre and the matrix is usually epoxy. Damage One of the main disadvantages with the use of composites is the difficulty to tell if damage has occurred within it, this can be known as barely visible damage. This is due to the way in which the composite structure is manufactured and that the majority of the damage will occur behind the surface. The surface of the composite may only seem to have a small bit of damage, such as a bit of scratched paintwork, while behind it the inside of the structure has been badly damaged. Delamination can happen due to moisture being able to go through the surface of the composite. If this moisture freezes, which can occur at high altitudes, it will start to force the layers of the composites apart. This could continue to occur if undetected causing serious damage to the composite structure. Fibre damage, where the fibres within the reinforcing material break, and matrix damage, where the matrix splits, may also occur if there is damage to the composite. Inspection There are several ways of testing for damage to composites. The simplest one of these is tap testing. This is where the surface of the composite is tapped using either a light hammer or a coin. An area of which is undamaged will make a ringing sound where as a duller note will be heard if the area is damaged. A more accurate version of this method can be had with the use of an electronic tap tester. Other methods of detecting damage are with the use of ultrasonic or x-ray machines. All these forms of testing are known as non destructive testing. This is due to no damage is needed to be made to the component getting tested by any of these methods. Repair Unlike Aluminium which can withstand damage and still be useable, composites when damaged have to be either repaired or replaced immediately. Repairing a composite panel is considerably more difficult than repairing an aluminium panel. This means that the repair will take a longer time in comparison, and will mean that the aircraft will be out of service longer. The cost of the materials to replace the damaged part is also more expensive, and may not be available at the airport where the damage is detected. Special training for working with composites may also be needed, resulting in even greater costs for the airline operator. Lightning Strikes The use of metal wing skins meant that if there was a lightning strike on the aircraft, it would be dispersed over the whole body of the aircraft and would dissipate at the end of the wings, through static dischargers, due to its conductive nature. The problem with the use of some composites as a wing skin is that they are considerable less conductive compared to a metal wing skin. Therefore, this could lead to damage occurring to the composite panel as the intensity of the lightning strike would be concentrated on the spot it hit as there would be no way for the energy to disperse due to the non conductive nature of the composite. The main danger of this is that the energy of the lightning bolt may be able to penetrate through the surface of the skin enough to produce a spark inside the wings where the fuel tanks are. This spark could cause the fuel vapour within the tanks to ignite, causing an explosion within the wing. Boeing have created several ways to prevent this scenario from occurring within their 787 dreamliner. The main method is having a thin metal mesh on the outside of the composite. This causes the composite skin panel to act in the same way as the metal one, and disperse the energy of the lightning strike over the whole surface of the aircraft. They also make sure that each fastener holding the composite skin panel to the wing structure is tightly fitting, preventing sparking from occurring between the spaces. Edge sealant will also be used to make sure there are no gaps present, and can be of either a glass fibre or goop. The use of a nitrogen generating system will be used to add nitrogen into the fuel tank, which will mix with the fuel vapours creating a safer non-flammable mixture should a spark occur. Future Materials New materials are continually being created by the aviation industry to try and lighten their aircrafts, and thus making them more appealing to airline operators. There has been increased competition to try and make composite materials which can be used throughout an aircraft. Other manufacturers are looking for slightly different ways to improve on materials that are available at present, with the use of shape memory alloys. Composite Spar Al/Composite The continued development of composites has lead to the creation of a material which incorporates both aluminium and composite. This material would be ideal for the use in aircraft wings due to several properties in which it possesses. The main one being that it is virtually fully resistant to metal fatigue. Metal fatigue comes about due to the cyclic loading of material. This will lead to a failure of the metal after a crack starts within the component then increases in size. This is relevant in aircraft wings as they experience cyclic loading as the lift generated by them changes during flight, such as take off and during patches of turbulence. Compared to the manufacturing costs of composites, the manufacturing costs of this material are significantly lower. As well as this, repairs to damaged sections are more straightforward compared to composites, which reduce the cost. The strength properties in which this material holds are greater than the composites which are used in aircraft wings at the present time. The most noticeable being the Boeing 787 which incorporates carbon fibre reinforced plastic. Due to this increased strength, the thickness of the material needed can be reduced and this can lead to a weight saving of around twenty percent, which is equivalent of between 600 to 800kg. This reduction in weight will cause a reduction in fuel use, along with the reduction in maintenance cost will reduced the overall running costs imposed on the airline operator. Morphing wing Shape memory alloys have existed for a reasonable long time, but it is only recently in which it has found a purpose within the airline industry. The use of shape memory alloys within the manufacture of aircraft wings is being looked at to improve the efficiency of the wing. This would happen as the flight crew would be able to change the shape of parts of the wing during different flight operations. There has been research into the development of a fully morphing wing and also that of a morphing winglet. Both of these ideas would lead to several advantages, but there are also disadvantages of the use of shape memory alloys. The main advantage of this material is that it can remember its shape after being deformed. When the material has been deformed, if the material is then heated to a certain temperature it will return to original shape. These materials also incorporate the property of Pseudo elasticity, which is super elasticity. This is when if the alloy is subjected to load it will stretch and change form. The load imposed on the material will then be absorbed, and it will return to its original form and shape. Shape memory alloys, such as Nickel Titanium, can be polished to give very smooth finishes resulting in a reduction in drag as the air flows over it. There are disadvantages which hold up the development of shape memory alloys, which include the difficulty and the cost of manufacture. The main problem with the use of this material in aircraft wings is that it does not have very good fatigue properties, which one needs. A shape memory alloy is manufactured to the shape in which it will take when heat is applied to it. As the reactivity of titanium is high, the use of a vacuum during manufacture is common. Hot working is one of the methods used to create these types of alloy and is where the material is heated up to temperatures of 900oc and then shaped. Cold working is another method that can also be used, but comes with the disadvantage that the material need constant heat treatment due to work hardening occurring. The use of this material in winglets would allow the winglets to change shape depending on the flight conditions such as the relative airspeed of the aircraft. This would allow them to have the most efficient angle between them and the wing. A reduction in wing vortices would then be able to occur over each flight operation. The drag experience on the aircraft at each point would be minimised, in turn reducing the fuel consumption of the aircraft as less thrust is required to move the aircraft would decrease. The idea of the winglets flattening out during takeoff and landing is also being examined as the wing would produce more lift at the slower speeds. This means there would be a reduction of noise generated from the engines as less thrust would be required. Constructing a wing out of smart alloy materials has been look at as it could lead to several advantageous properties, such as weight saving and reduction in drag. This means that the wing could change shape during flight operations to make them more efficient. The wing surface would be continuous as there would be no gaps in between flap and the surface would be smoother as there would be fewer rivets needed. This would result in a reduction of drag generated from the surface of the wing. A reduction in weight could be seen from the removal of the hydraulic system needed to move the control surfaces of the wing at present. There has also been investigation into using the shape memory alloy for use in just the leading and trailing edges as a replacement for the traditional metal flaps. The overall result of using shape memory alloys to replace traditional wings would be better fuel consumption as there would be a reduction of drag and weight. Discussion Conclusion I recommend that there should be a continued development of composites within the airline sector. This will lead to the manufacture of composites which are strong enough to be used on the main structural parts of the wings, and which could also be used on other components of the aircraft. The more widely use of composites would also lead to a reduction of weight of the aircraft, making them more fuel efficient and more environmentally friendly. This would also be an advantage for the airline company as there would be a reduction in the amount of fuel needed resulting in reduced running costs.

Analysis of War Photography

Analysis of War Photography War photography has existed since the nineteenth century, when Roger Fenton set out to photograph the Crimean war in 1855. From the beginning of war photography questions have always been raised about their representation of the truth. Compared to modern day cameras the exposure time required to take a photograph ensured that action shots were not possible. The images could only be of dead on the battlefield or posed for. This was apparent throughout Alexander Gardeners photos of the American Civil. The photographer, who created the book Photographic Sketch Book of the Civil War, was famed for staging various shots. The image which was captioned, The home of a rebel sharpshooter was proved to have been staged. Civil war experts reviewed the image revealing that Gardner had dragged the body into the shot and twisted his head towards the camera. The gun also within the image was placed strategically by Gardner. During World War two the staging of photographs continued. The cameras used during this war were a significant improvement and allowed for action shots to be taken but still questions were being asked about the authenticity of some of the photographs. Yevgeny Khaldeis famous photograph of a Soviet soldier placing the Soviet Unions flag atop of the Reichstag building in Berlin was in fact staged. The photo was taken three days after the Soviets had firstly placed a flag at the top. The image was taken at such an angle to prevent showing other Soviet soldiers who were looting and the soldiers were handpicked by Khaldei. Another of a photo which is circled by rumours of being staged is the most reproduced photo in the world. Jim Rosenthals photo of the flag rising at Iwo Jima was claimed to be, too perfect. The image taken was not the first picture of a flag being raised. Marine Photographer took the first picture of a flag being raised earlier in the day while the marine were under heavy fire. Rosenthals photo was taken later in the day and pictured a much larger flag. There has always been a partiality of representation in major wars simply because usually only one side is reported on by journalists representing news institutes from the same country as the army they report on. This begs the question of what is the purpose of war photography. Is it to inform the public or to provide morale for troops and the home public? The purpose of war photography has shifted throughout the years. During earlier wars photos were purely used to inform the public. Images were sent back to keep the public updated on what their troops were doing. In contrast, recent war photography, due to censorship and embedding, has become nothing more than propaganda. Staged and altered shots are created in order to show the military in a positive light, therefore limiting the offence they create to the viewing public. Other factors need to be taken into account, in order to determine whether war reporting is purely for morale of the country or to inform the public, such as the safety of the nation. For instance the World wars threatened national survival, so therefore reports and photographs released and published were intended to create a sense of morale and keep the war effort going. This was mainly as everyone would have been affected by the war., while wars being fought in foreign countries such as Iraq and Afghanistan lead to a sense of anonymity as it is out of direct view of the public. Reports and images published from these photojournalists need to carry a certain amount of truth to inform the public back in their home countries. The Vietnam War is known as the war that was lost on TV. The media was allowed to publish all kinds of images. During Vietnam the press was given remarkable freedom to report the war without any government control. Vietnam was the most heavily covered war in which reporters were not subject to extensive censorship. Pictures of decapitated bodies and civilians injuries were being broadcast back in America causing the public to think twice about the war that was taking place. President at the time Richard Nixon stressed this issue by saying, In each nights TV news and each mornings papers the war was reported battle by battle, but little or no sense of the underlying purpose of the fighting was conveyed. Eventually this contributed to the impression that we were fighting in military quicksand, rather than toward an important and worthwhile objective. The severity of the images was one of many factors that contributed to the American government losing the will to fight on in the war. Many journalists generally reported what they saw both positive and negative, according to James Reston, journalists didnt think it was their mission to serve the war effort. The freedom they were given was interpreted in several different ways, with the majority reporting the war in a completely subjective way. Reston goes onto say, for better or worse it was the journalists views that prevailed with the public, whose disenchantment forced an end to American involvement. This was especially prominent in independent photographers, as they would not have an editorial agenda to adhere to. Inevitably during military briefings they would lose the idea of the big picture. Although it can be argued that military briefings are often thinly disguised as propaganda anyway. The general stance on reporting the war started to change as the war progressed. The longer the conflict continued the more graphic the images and reports were. The offensive and disturbing reports from Vietnam as well as conscription and the fatality rate led to many people staging an anti war protest and voicing their concerns about the war. The largest of which was at Washington DC when a reported two hundred and fifty thousand people gathered in joint protest. Although it is claimed to be one of the contributing factors Professor Daniel Hallin of the University of California at San Diego conducted a study into the Vietnam coverage. He concluded that the war coverage was almost completely sanitised on television, due to the need not to cause any offence to any of the soldiers families. As a response to what happened in Vietnam, the censorship put upon the press by the British government during the Falklands war was at an extreme. Every inch of columns and pictures had to be check thoroughly by army officials before it was then passed onto the Ministry of Defence, who then proceeded to check it again before it could be published. The censorship in the Falklands was so extreme that it led to the word censored actually being censored. Due to the negative press that was created throughout Vietnam, the British government made a deliberate attempt to stop people knowing what was going on. The government were keen to project a positive picture back the British public and it did this by starving the press of any influential information. This was evident on the 14th of May 1982 when an Exocet missile hit HMS Sheffield. The military ensured that the news was delayed in reaching the reporters present. All reporters were also kept at arms length any live footage sent back to Britain was shot from a few hundred metres away. Very few clear picture of HMS Sheffield were shown back in Britain. Before the invasion of Iraq it was decided that journalists would be embedding among soldiers The concept of embedding reporters was an initiative proposed by the US defence secretary Donald Rumsfeld. The concept was introduced after initial pressure from the countrys news media. The press were disappointed with the level of access that they were granted in previous conflict zones. The concept of Embedding reporters was not a new on but it was never carried out on this kind of scale before. After deciding to embed reporters among soldiers Rumsfeld explained the reasoning behind his decision, We need to tell the factual story-good and bad-before others seed the media with disinformation and distortion, as they most certainly will continue to do. Our people in the field need to tell our story-only commanders can ensure the media get to the story alongside the troops. The main concept of embedding reporters is that they would identify with the troops around them. Each journalist would be assigned to a company of soldiers and would experience the war first hand in the frontline. Each reporter would be issued with military equipment; they would also eat and sleep alongside their respective soldiers. By assigning a journalist to a troop, it meant that the reporter could be placed anywhere. This meant that the position of the embed could be decided by the military. Around six hundred national and local journalists were embedded with troops as they entered Iraq. The system of embedding reporters tended to have a psychological effect upon reporters causing them to lose the ability to remain objective. The system also led to reporters having tunnel vision especially when reporting on tactical operation. Journalists would only see one or two units in action, and therefore only reporting upon what they were doing. Gordon Dillow an embedded reported said, I fell in love with my marines I wasnt reporting; the point was I was reporting the Marine grunt truth which had also become my truth. The following images and articles will be analysed using Roland Barthes theory of semiotics. Building upon Ferdinand de Saussures linguistic theories Barthes constructed his own theory of semiotics. According to his paper Myth today (1957) the theory consists of a signifier, the signified and the sign. The signifier is the term used to describe the image, which is being examined, and the signified is the term used to describe any ideas which are raised by the signifier, and the sign is the correlation of the signifier and the signified. Barthes also noted that anything signified by the signifier is culturally specific, Signifieds have a very close communication with culture, knowledge, history, and it is through them so to speak, that the environmental world invades the system. Barthes (1967) This would suggest that whatever is being signified may change over time and that different people would interpret signifieds differently. For example within an Indian culture cows are perceived as a sacred holy animal, while in western culture the cow is simply a provider of food. Due to the fact that each signified is culturally specific Barthes theory also takes into account the uses of denotation and connotation. Denotation is a literal description of the image or object being examined while connotation is the ideas associated with the image or object. When analysing press photographs it is important to also include the caption, as Barthes claims that the image and the caption are two different structures. Barthes uses the terms anchorage and relay when referring press photograph captions. Anchorage refers to when the text within the caption, directs the reader through the signifieds of the image causing him to avoid some and receive others. Barthes (1977). Relay describes the addition of something in the caption, which is not actually present in the image. Barthes also included in his theory of semiotics the element of myth. Myth is described as, a second-order semiological system. Barthes argues that signification is divided into two different sections connotations and denotation and myth is signification in the connotative level. Myth sees the signifiers in its raw form. Similar to signifieds myth is divided into two categories, the language object which is the linguistic system and myth itself which is described as metalanguage because it is a second language which talks about the first one. Barthes described the use of myth as, When he reflects on a metalanguage, the semiologist no longer needs to ask himself questions about the composition of the language object, he no longer has to take into account the details of the linguistic schema; he will only need to know its total term or global sign (Barthes 1967) When using Barthes theory two competing myths can be attained about war. One myth is based upon General William Tecumseh Shermans quote that reads, It is only those who have neither fired a shot nor heard the shrieks and groans of the wounded who cry aloud for bloodWar is hell. The competing myth to this is that war can be fought in a morally acceptable way. Making a war morally manageable is minimising the risk to casualties and soldiers and hence political and electoral risks to their masters. By using various photographs and articles from differing conflicts such as Vietnam, the Falklands, and Afghanistan, this essay will use Barthes theory of semiotics to test the theory that images from non embedded reporters will support the myth that war is hell and embedded photographers will show that war can be fought in a morally acceptable way.

Antony and Cleopatra :: essays research papers

‘Antony and Cleopatra’. The simplicity of the Jacobean Stage and its lack of scenery focused the audiences’ attention on the actors. Discuss how Shakespeare created the grandeur of the Worlds of Rome and Egypt, and the magnificence of the protagonists, through his use of imagery in ‘Antony and Cleopatra’. The play of ‘Antony and Cleopatra’ was written in 1606, and is mainly set in their respective worlds of Rome and Egypt. ‘Antony and Cleopatra,’ like Shakespeare’s other plays was written to be performed on the Jacobean Stage. In Shakespeare’s time there was a lack of scenery and stage props, but he compensated with his use of language that he gave to the audience, to assist them, bring to life the characters, plot and the setting in their own minds. That was the past, here and now in the present, we go to the Cinema, which is full of special effects, computerised graphics, and exciting camera shots, which all goes towards creating a typical Hollywood blockbuster film. With ‘Antony and Cleopatra this is not necessary as it is still more effective on the stage than on screen, which is due to the elaborate language used, which tests our imagination. Shakespeare’s plays are written in dramatic verse and his use of imagery is very effective, as it engages the audiences’ attention, to give them a deeper meaning and reality to each and every character. In order to analyse how Shakespeare uses imagery to describe Antony and his world of Rome, and Cleopatra and her world of Egypt, it is necessary to look at how he breathes life into their larger than life personalities by the use of powerful, vivid language. The opening speech raises the audiences’ awareness of the Roman view towards Antony and Cleopatra’s relationship. â€Å"You shall see him The triple pillar of the world transformed into a strumpet’s fool,† which ultimately means that Antony is Cleopatra’s jester, that would do anything for her and that his imminent downfall is due to Cleopatra the â€Å"Strumpet†. Mark Antony’s character at the beginning of the play, is that of a great, powerful, triumvir whose heart has been entrapped by Cleopatra’s enchanting personality. The audience hears many good things about Antony’s character, which is shown through his great past, â€Å"It is reported thou didst eat strange flesh which some did die look on,† which informs us that he was a great warrior which evoke feelings of respect towards him.

Race And Law In Philadelphia :: essays research papers

RACE AND THE LAW IN PHILADELPHIA   Ã‚  Ã‚  Ã‚  Ã‚  If you’re ever driving down I-95 through Philadelphia, you will notice an exit for Allegheny Avenue. Allegheny Ave is one of the most dangerous parts of Philly you can drive through. Predominantly black with some Puerto Ricans and a handful of whites, Allegheny is situated between the Delaware River and abandoned industrial complexes. Windows are kept closed and doors are locked as you drive past bums, drug dealers, scorched abandoned cars, sleazy strip bars, cops and crack heads. You can buy cocaine and marijuana on almost every side street just by driving down with your window rolled down. Corners with lots of shoes hanging from a single telephone poll advertise heroin and crack. Once you drive under the L-train, you can amuse yourself by playing the spot-the-prostitute-game. Paddy wagons are never parked to far away and cops patrol by, ignoring the misdemeanors around them and just trying to make worthwhile arrests.   Ã‚  Ã‚  Ã‚  Ã‚  If you go no more than 20 minutes west, you’ll end up in Manyunk, which is directly on the border of Philadelphia, and to residents, is considered part of it. Unlike Allegheny Ave, the main street is littered with import stores, hip coffee houses, yuppie bars and colorful banners that welcome you to the town. It’s a perfect place for happy couples and families to go for shopping, dinning, and entertainment. The surrounding neighborhoods mainly consist of white people who have grown up in Philadelphia. There are plenty of barking dogs, swing sets and kids who play street hockey without a worry besides being home by dinner. The families are mainly blue-collar workers that are able to send their kids to parochial schools. Everyone knows everyone else in the neighborhood and you get the sense that people watch out for each other. Occasionally a cop will patrol by but nothing ever really goes on besides the occasional breaking of the noise curfew. All in all, there isn’t a lot of law enforcement there because there doesn’t need to be.   Ã‚  Ã‚  Ã‚  Ã‚  You’re probably wondering why these two neighborhoods are different. A lot of different factors come into play but I will attempt to explain it anyway. First, environment definitely seems to be a big factor in the direction a community will take. Allegheny Ave is pretty much detached from a lot of the city. The schools are seriously over-crowded and are known to be dangerous.

Examine different sociological views on the change of child

There is really only two views on the change of childhood and they're ‘The march of progress view and ‘The conflict view' both of which are every different to the other. The march of progress view is the view that the position of children In western societies has greatly improved. Aries and shorter , two sociologists of whom hold a march of progress view, argue that children are more valued , better cared for , are more protected and educated , have better healthcare and have more rights all due to sociological changes throughout history.These Include things such as laws estricting child labour, the establishment of policies controlling at what age a child can do things (such as smoke), the introduction of compulsory schooling (1880) , new child protection and welfare legislations and the growth of the idea of children's rights. Lloyd deMause , a social thinker of whom seemed to hold a march of progress view , said In 1974 that ‘ The history of childhood Is a nightm are from which we are Just recently awakening from'. Other sociologists of whom agree with this argue that this Is because not only has society changed as a whole due to new laws, legislations and iews etc. ut also because families seemed to have become more child centred as well as society as a whole. This Is clear as children are no longer to be seen and not heard as they where in Victorian times. They also argue that children are given a better chance of survival due to the development of proper healthcare and higher standards of living thus making childhood better. Many people hold the conflict view that childhood Is quickly disappearing , Iona ople argues against this as through her lifelong research she has found strong evidence hat there Is a very separate culture between adults and children of which didn't exist 50 years ago.The opposing view to that of the marching progress view is the conflict view. This is the view of which Is , held by feminists and Marxists, that childh ood hasn't improvised. Sociologists of whom hold the conflict view argue that one of the main reasons childhood hasn't improved is due to Inequality between both children and adults. They argue that children from different status's , nationalities , gender , ethnicity and class do not have the same resources , chances or backgrounds herefore leaving them unequal.For example according to Mayer Hillman (1993) boys are more likely to be allowed to cross or cycle on roads, use buses and go out in the dark unaccompanied , whereas Jens Bonke (1999) found that girls do more housework than boys , so much so that in some families girls do five times more than the boys in inequality through ethnicity was discovered by Julia Brannens (1994), she found through her study of 15-16 year old girls that Asian parents were more likely than others to be strict towards their daughters.They also argue that there is also inequality between adults and children therefore causing children to experience more control and oppression to that of a child 50 years ago. March of progress writers argue that adults use this power of inequality to the benefit and protection of children. However , critics such as Shulamith Firestone (1979) and John Holt (1974) argue that many things march of progress writers see as care and protection are in fact Just new ways to to force control and injustice on Modern age children.For example Firestone argues that ‘protection' of hildren from paid work is not a form of protection on a child but in fact a way of keeping them dependant on their parents and forcibly creating a segregation between adults and children, of which again is a form of inequality. Another reason they believe childhood hasn't improved is due to the control children experience. Due to the change in society through history and the segregation between adult and children it is seen that adults have more authority over their children, therefore allowing them to control certain aspects of their lives.Such as the pace/places children are and aren't allowed to go, what their child spends time doing and how much time there child spends doing things, there child's bodies and the ways in which they and other people can touch them and the resources their child receives. For example people are allowed to put signs up saying â€Å"no school children† or can band there child from entering a particular estate or place. They can also disallow there child to go out at specific times or set them a time in which they do distinct tasks such as homework or chores.They can also tell a child how to wear here hair or what clothes they can and cannot wear and they can also disallow a child access to the internet etc. These things alone do not come across as an issue but when put together sociologists argue that these things stops the independence of a child and and can even cause a child to be unhappy. Another thing sociologists argue and that isn't rare is that adult control can often lead to abuse in many levels. This can be in 4 different forms physical abuse , emotional abuse, sexual abuse and neglect all seen even in modern day (Daniel Pelka, Baby P etc. ).Another thing sociologists argue that childhood hasn't improved is the way in which technology has taken over our children's lives even in such a way they are constantly glued to a television or games console. This then effects their behaviours and learning abilities which can lead to loss of imagination, shortening of attention span and may cause confusion with fact and knowledge. Sue palmer also found that there where many concerns with teachers as computer games and television was causing children to become more impulsive and distractable therefore compromising ntellectual,emotional and social development.A particular sociologists Neil Postman believed that childhood was disappearing due due to telivisation unsupervised child hood games and rhymes etc. where disappearing therefore children's child hoods where beginning to fade away. In my own opinion I believe in neither the conflict view or the march of progress view as there is lots of little things you have to take into consideration like the way in which life as a whole has changed , for example the fact that theirs at least a case of murder , rape or abduction on the news every single week.Most parents feel as if they have to protect they're children from this and rightfully so. Although some parents may be stricter with they're children than others and some more over protective they all have they're own personal reasons for that. Some parents are strict because they simply want they're children to succeed whereas other because that's the way in which they where brought up. Some parents are more overprotective than other as they only have one child or simply because they're terrified of the disgusting and horrific things that happen here even in the modern era.On one hand I believe that childhood has improved as children are no longer working from the age of 3 and are now given a chance to mature before being pushed into the world of work. On the other hand I think particular aspects of childhood life hasn't improved as children as still being neglected and abused and are very much so reliant on there parents sometimes when they don't actually need to be , also a lot of independence and freedom is being taken away from children from no fault of they're own. So overall I believe in some aspects childhood has improved in others not so much.

Assembly Language

ASSEMBLY LANGUAGE An assembly language is a low-level programming language for a computer, microcontroller, or other programmable device, in which each statement corresponds to a single machine code instruction. Each assembly language is specific to a particular computer architecture, in contrast to most high-level programming languages, which are generally portable across multiple systems. Assembly language is converted into executable machine code by a utility program referred to as an assembler; the conversion process is referred to as assembly, or assembling the code.Assembly language uses a mnemonic to represent each low-level machine operation or opcode. Some opcodes require one or more operands as part of the instruction, and most assemblers can take labels and symbols as operands to represent addresses and constants, instead of hard coding them into the program. Macro assemblers include a macroinstruction facility so that assembly language text can be pre-assigned to a name, and that name can be used to insert the text into other code. Many assemblers offer additional mechanisms to facilitate program development, to control the assembly process, and to aid debugging.HISTORY OF ASSEMBLY LANGUAGE Assembly languages date to the introduction of the stored-program computer. The EDSAC computer (1949) had an assembler called initial orders featuring one-letter mnemonics. Nathaniel Rochester wrote an assembler for an IBM 701 (1954). SOAP (Symbolic Optimal Assembly Program) (1955) was an assembly language for the IBM 650 computer written by Stan Poley. Assembly languages eliminated much of the error-prone and time-consuming first-generation programming needed with the earliest computers, freeing programmers from tedium such as remembering numeric codes and calculating addresses.They were once widely used for all sorts of programming. However, by the 1980s (1990s on microcomputers), their use had largely been supplanted by high-level languages, in the search for improved programming productivity. Today assembly language is still used for direct hardware manipulation, access to specialized processor instructions, or to address critical performance issues. Typical uses are device drivers, low-level embedded systems, and real-time systems. Historically, a large number of programs have been written entirely in assembly language. Operating systems were ntirely written in assembly language until the introduction of the Burroughs MCP (1961), which was written in ESPOL, an Algol dialect. Many commercial applications were written in assembly language as well, including a large amount of the IBM mainframe software written by large corporations. COBOL, FORTRAN and some PL/I eventually displaced much of this work, although a number of large organizations retained assembly-language application infrastructures well into the '90s. Most early microcomputers relied on hand-coded assembly language, including most operating systems and large applications.This was because these systems had severe resource constraints, imposed idiosyncratic memory and display architectures, and provided limited, buggy system services. Perhaps more important was the lack of first-class high-level language compilers suitable for microcomputer use. A psychological factor may have also played a role: the first generation of microcomputer programmers retained a hobbyist, â€Å"wires and pliers† attitude. In a more commercial context, the biggest reasons for using assembly language were minimal bloat (size), minimal overhead, greater speed, and reliability.Typical examples of large assembly language programs from this time are IBM PC DOS operating systems and early applications such as the spreadsheet program Lotus 1-2-3. Even into the 1990s, most console video games were written in assembly, including most games for the Mega Drive/Genesis and the Super Nintendo Entertainment System. According to some industry insiders, the assembly language was the best computer language to use to get the best performance out of the Sega Saturn, a console that was notoriously challenging to develop and program games for.The popular arcade game NBA Jam (1993) is another example. Assembly language has long been the primary development language for many popular home computers of the 1980s and 1990s (such as the Sinclair ZX Spectrum, Commodore 64, Commodore Amiga, and Atari ST). This was in large part because BASIC dialects on these systems offered insufficient execution speed, as well as insufficient facilities to take full advantage of the available hardware on these systems.Some systems, most notably the Amiga, even have IDEs with highly advanced debugging and macro facilities, such as the freeware ASM-One assembler, comparable to that of Microsoft Visual Studio facilities (ASM-One predates Microsoft Visual Studio). The Assembler for the VIC-20 was written by Don French and published by French Silk. At 1,639 bytes in length, its author believes it is the smallest symbolic assembler ever written. The assembler supported the usual symbolic addressing and the definition of character strings or hex strings.It also allowed address expressions which could be combined with addition, subtraction, multiplication, division, logical AND, logical OR, and exponentiation operators. COMPILER A compiler is a computer program (or set of programs) that transforms source code written in a programming language (the source language) into another computer language (the target language, often having a binary form known as object code). The most common reason for wanting to transform source code is to create an executable program.The name â€Å"compiler† is primarily used for programs that translate source code from a high-level programming language to a lower level language (e. g. , assembly language or machine code). If the compiled program can run on a computer whose CPU or operating system is different from the one on which the compiler r uns, the compiler is known as a cross-compiler. A program that translates from a low level language to a higher level one is a decompiler. A program that translates between high-level languages is usually called a language translator, source to source translator, or language converter.A language rewriter is usually a program that translates the form of expressions without a change of language. A compiler is likely to perform many or all of the following operations: lexical analysis, preprocessing, parsing, semantic analysis (Syntax-directed translation), code generation, and code optimization. Program faults caused by incorrect compiler behavior can be very difficult to track down and work around; therefore, compiler implementors invest significant effort to ensure the correctness of their software.The term compiler-compiler is sometimes used to refer to a parser generator, a tool often used to help create the lexer and parser. INTERPRETER In computer science, an interpreter normall y means a computer program that executes, i. e. performs, instructions written in a programming language. An interpreter may be a program that either 1. executes the source code directly 2. translates source code into some efficient intermediate representation (code) and immediately executes this 3. xplicitly executes stored precompiled code made by a compiler which is part of the interpreter system While interpreting and compiling are the two main means by which programming languages are implemented, these are not fully mutually exclusive categories, one of the reasons being that most interpreting systems also perform some translation work, just like compilers. The terms â€Å"interpreted language† or â€Å"compiled language† merely mean that the canonical implementation of that language is an interpreter or a compiler; a high level language is basically an abstraction which is (ideally) independent of particular implementations.ASSEMBLER Assembler (meaning one that a ssembles) may refer to: It is a computer program that translate between lower-level representations of computer programs; it converts basic computer instructions into a pattern of bits which can be easily understood by a computer and the processor can use it to perform its basic operations Assembly Language Syntax Programs written in assembly language consist of a sequence of source statements. Each source statement consists of a sequence of ASCII characters ending with a carriage return.Each source statement may include up to four fields: a label, an operation (instruction mnemonic or assembler directive), an operand, and a comment. The following are examples of an assembly directive and a regular machine instruction. PORTA equ $0000; Assembly time constant INP ldaa PORTA; Read data from fixed address I/O data port An assembly language statement contains the following fields. Label Field can be used to define a symbol Operation Field defines the operation code or pseudo-op Operand Field specifies either the address or the data.Comment Field allows the programmer to document the software. Sometimes not all four fields are present in an assembly language statement. A line may contain just a comment. The first token in these lines must begin with a star (*) or a semicolon (;). For example, ; This line is a comment * this is a comment too * This line is a comment Instructions with inherent mode addressing do not have an operand field. For example, label clra comment deca comment cli comment inca comment DATA TYPES IN ASSEMBLY LANGUAGEThere is a large degree of diversity in the way the authors of assemblers categorize statements and in the nomenclature that they use. In particular, some describe anything other than a machine mnemonic or extended mnemonic as a pseudo-operation (pseudo-op). A typical assembly language consists of 3 types of instruction statements that are used to define program operations: †¢Opcode mnemonics †¢Data sections †¢Assembly directives Opcode mnemonics and extended mnemonics Instructions (statements) in assembly language are generally very simple, unlike those in high-level language.Generally, a mnemonic is a symbolic name for a single executable machine language instruction (an opcode), and there is at least one opcode mnemonic defined for each machine language instruction. Each instruction typically consists of an operation or opcode plus zero or more operands. Most instructions refer to a single value, or a pair of values. Operands can be immediate (value coded in the instruction itself), registers specified in the instruction or implied, or the addresses of data located elsewhere in storage.This is determined by the underlying processor architecture: the assembler merely reflects how this architecture works. Extended mnemonics are often used to specify a combination of an opcode with a specific operand, e. g. , the System/360 assemblers use B as an extended mnemonic for BC with a mask of 15 and NOP for BC with a mask of 0. Extended mnemonics are often used to support specialized uses of instructions, often for purposes not obvious from the instruction name. For example, many CPU's do not have an explicit NOP instruction, but do have instructions that can be used for the purpose.In 8086 CPUs the instruction xchg ax, ax is used for nop, with nop being a pseudo-opcode to encode the instruction xchg ax, ax. Some disassemblers recognize this and will decode the xchg ax, ax instruction as nop. Similarly, IBM assemblers for System/360 and System/370 use the extended mnemonics NOP and NOPR for BC and BCR with zero masks. For the SPARC architecture, these are known as synthetic instructions Some assemblers also support simple built-in macro-instructions that generate two or more machine instructions.For instance, with some Z80 assemblers the instruction ld hl, bc is recognized to generate ld l, c followed by ld h, b. These are sometimes known as pseudo-opcodes. Data sections There are instructions used to define data elements to hold data and variables. They define the type of data, the length and the alignment of data. These instructions can also define whether the data is available to outside programs (programs assembled separately) or only to the program in which the data section is defined. Some assemblers classify these as pseudo-ops. Assembly directivesAssembly directives, also called pseudo opcodes, pseudo-operations or pseudo-ops, are instructions that are executed by an assembler at assembly time, not by a CPU at run time. They can make the assembly of the program dependent on parameters input by a programmer, so that one program can be assembled different ways, perhaps for different applications. They also can be used to manipulate presentation of a program to make it easier to read and maintain. (For example, directives would be used to reserve storage areas and optionally their initial contents. The names of directives often start with a dot to disti nguish them from machine instructions. Symbolic assemblers let programmers associate arbitrary names (labels or symbols) with memory locations. Usually, every constant and variable is given a name so instructions can reference those locations by name, thus promoting self-documenting code. In executable code, the name of each subroutine is associated with its entry point, so any calls to a subroutine can use its name. Inside subroutines, GOTO destinations are given labels. Some assemblers support local symbols which are lexically distinct from normal symbols (e. . , the use of â€Å"10$† as a GOTO destination). Some assemblers provide flexible symbol management, letting programmers manage different namespaces, automatically calculate offsets within data structures, and assign labels that refer to literal values or the result of simple computations performed by the assembler. Labels can also be used to initialize constants and variables with relocatable addresses. Assembly lang uages, like most other computer languages, allow comments to be added to assembly source code that are ignored by the assembler.Good use of comments is even more important with assembly code than with higher-level languages, as the meaning and purpose of a sequence of instructions is harder to decipher from the code itself. Wise use of these facilities can greatly simplify the problems of coding and maintaining low-level code. Raw assembly source code as generated by compilers or disassemblers—code without any comments, meaningful symbols, or data definitions—is quite difficult to read when changes must be made. MacrosMany assemblers support predefined macros, and others support programmer-defined (and repeatedly re-definable) macros involving sequences of text lines in which variables and constants are embedded. This sequence of text lines may include opcodes or directives. Once a macro has been defined its name may be used in place of a mnemonic. When the assembler p rocesses such a statement, it replaces the statement with the text lines associated with that macro, then processes them as if they existed in the source code file (including, in some assemblers, expansion of any macros existing in the replacement text).Note that this definition of â€Å"macro† is slightly different from the use of the term in other contexts, like the C programming language. C macros created through the #define directive typically are just one line or a few lines at most. Assembler macro instructions can be lengthy â€Å"programs† by themselves, executed by interpretation by the assembler during assembly. Since macros can have ‘short' names but expand to several or indeed many lines of code, they can be used to make assembly language programs appear to be far shorter, requiring fewer lines of source code, as with higher level languages.They can also be used to add higher levels of structure to assembly programs, optionally introduce embedded debu gging code via parameters and other similar features. Macro assemblers often allow macros to take parameters. Some assemblers include quite sophisticated macro languages, incorporating such high-level language elements as optional parameters, symbolic variables, conditionals, string manipulation, and arithmetic operations, all usable during the execution of a given macro, and allowing macros to save context or exchange information.Thus a macro might generate a large number of assembly language instructions or data definitions, based on the macro arguments. This could be used to generate record-style data structures or â€Å"unrolled† loops, for example, or could generate entire algorithms based on complex parameters. An organization using assembly language that has been heavily extended using such a macro suite can be considered to be working in a higher-level language, since such programmers are not working with a computer's lowest-level conceptual elements.Macros were used to customize large scale software systems for specific customers in the mainframe era and were also used by customer personnel to satisfy their employers' needs by making specific versions of manufacturer operating systems. This was done, for example, by systems programmers working with IBM's Conversational Monitor System / Virtual Machine (VM/CMS) and with IBM's â€Å"real time transaction processing† add-ons, Customer Information Control System CICS, and ACP/TPF, the airline/financial system that began in the 1970s and still runs many large computer reservations systems (CRS) and credit card systems today.It was also possible to use solely the macro processing abilities of an assembler to generate code written in completely different languages, for example, to generate a version of a program in COBOL using a pure macro assembler program containing lines of COBOL code inside assembly time operators instructing the assembler to generate arbitrary code. This was because, as wa s realized in the 1960s, the concept of â€Å"macro processing† is independent of the concept of â€Å"assembly†, the former being in modern terms more word processing, text processing, than generating object code.The concept of macro processing appeared, and appears, in the C programming language, which supports â€Å"preprocessor instructions† to set variables, and make conditional tests on their values. Note that unlike certain previous macro processors inside assemblers, the C preprocessor was not Turing-complete because it lacked the ability to either loop or â€Å"go to†, the latter allowing programs to loop.Despite the power of macro processing, it fell into disuse in many high level languages (major exceptions being C/C++ and PL/I) while remaining a perennial for assemblers. Macro parameter substitution is strictly by name: at macro processing time, the value of a parameter is textually substituted for its name. The most famous class of bugs resul ting was the use of a parameter that itself was an expression and not a simple name when the macro writer expected a name.In the macro: foo: macro a load a*b the intention was that the caller would provide the name of a variable, and the â€Å"global† variable or constant b would be used to multiply â€Å"a†. If foo is called with the parameter a-c, the macro expansion of load a-c*b occurs. To avoid any possible ambiguity, users of macro processors can parenthesize formal parameters inside macro definitions, or callers can parenthesize the input parameters.