The Central Processing Unit (CPU) is located inside the system unit. The CPU, also referred to as the central processor or processor, is the ‘brain’ of the computer. It heavily determines the data processing power of a computer. The CPU has two components:
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| There is also a small amount of memory, known as immediate access memory, associated with the CPU. The CPU uses this memory to perform the above operations. |  |
| As indicated above, the CPU determines the speed at which program instructions are carried out. The speed of the CPU is measured in megahertz (MHz) or gigahertz (GHz). 1 MHz is equal to 1 million cycles per second. 1 GHz is equal to 1 billion cycles per second. Each computer instruction requires a fixed number of cycles, so the speed of the CPU determines how many instructions per second the microprocessor can execute. The higher the MHz or GHz the faster the computer will execute program instructions. | |
Computers need some way of storing any data entered through the keyboard. This data is stored in the system memory of the computer. The system memory can be of two types - Random Access Memory (RAM) top and Read Only Memory (ROM) bottom. |
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It is of utmost importance to keep your data saved somewhere because the memory of the computer (RAM) is volatile that is once the computer is switched off it is lost. Since the internal memory (RAM) is temporary the information has to be stored on permanent media (disks or cartridges) referred to as secondary or backing storage. For this purpose we have a number of backing storage devices. The following table summarises the storage devices:
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Hard Disks are the main storage device in a computer system. They hold an enormous amount of data (120 Gb and more) and are very fast. On them we store our computer's operating system and software applications. They are usually found inside the system's unit but external ones exist as well. (top) |
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Floppy Disks can only store a very small amount of data (1.44 Mb). They are not very fast and not very reliable. However they are quite cheap and easy to carry. (top) |
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Compared to floppies CDs can hold a large amount of data (app. 700 Mb). Quite fast and reliable. Very cheap as well and easy to carry too. They are slowly replacing floppies.
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| DVD are similar to Cd Roms in appearance but can store a huge amount of data. A single sided, one layer CD holds 4.7 GB of data while a double sided DVD can reach 17 GB of storage. At the moment still a little expensive especially the DVD writer which is the peripheral used to write data on DVD's.(top) | |||||||||||||||||||||||||
A Zip disk is similar to a floppy in appearance. The main difference being that it can hold up to 250 Mb of data. Speed is also better than that of a floppy. (top) |
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Form 1 Concepts of Information Technology (continued) Slide the mouse over the images and read the notes. |
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