A computer has three basic parts – an input, the computing unit, an output. The computing unit, or the Central Processing Unit (CPU) consists of several units – Control Unit (CU), Arithmetic Logic Unit (ALU) and Main Memory Unit. Apart from that, a computer also has an auxiliary memory unit.
Now, what are these and how do they work?
Let’s say you are using a computer. You press ‘A’ on your computer, that means you are giving a command to show ‘A’ on your screen. What you did is gave your computer an instruction through an input device, i.e. your keyboard.
Now, you must think that computer is very smart and complex, but in reality a computer is a very simple and dumb, it cannot do anything on its own, and it is built on simple principles. A computer follows simple principles to do the tasks it is given, but it does the does extremely fast, and reliably. For example, your body is built using a simple unit – a cell. There are a handful of types of cells in your body. But there are a large number of them, and a large number of simple things create a complex mechanism. Same can be said for a computer. Though it uses simple principles, it does so a million times in a second which allows a computer to do complex tasks.
So, when you give your computer an instruction, that instruction is sent to the CPU. In the CPU, the Arithmetic Logic Unit (ALU) does the main processing or the calculation. The Control Unit (CU) controls the whole operation, as the name suggests. In other words, the CU is like the manager and the ALU is like the worker. But what does the memory unit do? As I said before, a computer is very dumb. It breaks down an instruction to simple bits and progresses through that; the CPU needs a Memory Unit to store the result of a task. Do all these seem complicated? Let us simplify it then.
Let’s imagine you are a computer. If I ask you, what is 2+2? You will simply answer, 4. But how did you do that? First, you heard that I asked you the question. Next your brain is told to calculate 2+2. You have learnt math when you were a child, so you apply that knowledge to calculate and you come up with the result: 4. So you memorise the result, then tell me the answer through your mouth.
Now let’s compare that with a computer. You open calculator in you computer and write 2+2 and press the ‘=’ button. As soon as you do that, you have fed an input to the computer. Then the instruction is sent to the CPU, which is the brain of the computer. After that, the Control Unit (CU) tells the Arithmetic Logic Unit (ALU) to calculate the answer. ALU uses the programming, which can be compared to your childhood learning, and calculates the answer. Then the answer is stored in the memory. Then the answer is sent to the display, where you see the answer: 4.
This was a very simple example of the workflow of a computer. A computer uses the same process every time an instruction is given. The faster a computer can do this, the more powerful it is.
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