TRANSCRIPTS
into a system, whatever its original form, has to be encoded. That means converted into a form that the system can store or process. Data, whether it is in the form of text, movement or sound, is stored as electrical signals which have one of two states, either on or off. The figure 1 is on, while the figure 0 is off. Each of these binary digits is called a bit.
Data that is input is then stored for later use, or processed. This is done by the microprocessor, also known as a CPU, or central processing unit. There are three parts to the CPU. These are the CU, or control unit, the ALU, which stands for arithmetic and logic unit, and the IAS, or immediate access store. The IAS holds data and programs which are needed for processing. The ALU performs calculations on data and the CU uses the results of these calculations, together with instructions held in its own data and programs, to make decisions about what to do with the calculations. For example, the calculations may be used to work out how much to pay employees in a company, or they may be used to switch on a system such as a central heating system.
Unit 3, Lesson 4, Exercise E≤1.19
Part 3 Let’s move on to output now. Output is what you get when a system has finished the processing stage. It is the result of data processing, which is then transmitted, or communicated, to the user. Output is the stage when data is decoded and once again becomes information which can be used by a person or another device. It might be a sound that alerts the police that someone is breaking into your house, a picture you can print out and display, or information about product sales that you can use to make decisions about the future of your company.
Some ICT systems operate as a cycle. A cycle is a continuous circle with no beginning and no end, although it can be broken if the system is switched off, or if there’s a problem. In a cycle, the output produced is used as feedback to input more data into the system, which is then processed. One such system is the cruise control system found in many of today’s cars. The system keeps the car travelling at a steady speed by increasing or decreasing the amount of fuel being fed into the car engine, depending on the input it receives.
Unit 5, Lesson 2, Exercise B≤1.20
Part 1 Good morning, everyone. This morning we’re going to learn about the early development of computing. In this first talk, I’m just going to give you an overview of the history of the computer up to the late 20th century, and then other key concepts will be dealt with in the next few lectures. Also, in your seminars and assignments, you’ll be able to cover all the important points in more detail. So ... er ... let’s see – yes – to start with, we need to look back to the early days of pre-mechanical computing. In other words, we’ll examine the early inventions which led eventually to our modern computer. These were ‘manual computers’, that is to say computers which were worked by hand. The first manual computer was the abacus, which was in fact an extension of the fingers on the hand. The ten fingers are the basis of the decimal system, of course. Another important pre-mechanical invention was known as Napier’s Bones. This was a series of rods which simplified and speeded up multiplication and division. Using the rods, it was possible to multiply numbers by using addition and to divide numbers using subtraction. Secondly, I’ll look at the transformation to mechanical computing, whereby computers used gears and cogs to carry out calculations. These include the Pascaline, which was invented by Blaise Pascal in France in 1645 to calculate taxes, and the Difference Engine, which was devised by Babbage and is seen by many as the birth of modern computing. By the end of the 19th century, many of these principles were still being used in the tabulating machine, which used punched cards to process data from the US Census. The company making these machines later became IBM, which all of you will have heard of. After that, I’ll talk about computing during the Second World War, particularly about the work of Alan Turing, an English scientist who devised a machine which could break German codes so that the English could read German military messages. The machine, known as Colossus, named after the noun ‘colossus’, which means a person or thing of great size, was built using electronic valves and relays. It worked very well and it was the world’s first electronic computer. Then I’ll discuss the development of electronic computers. These used transistors instead of valves, which greatly increased their performance and which would ultimately have a revolutionary effect on the speed and cost of computing. I’ll finish by mentioning some of the factors which led to the growth of the Internet. These include the speed of
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