What do you mean by organization of computer ? Explain each unit in detail. Or Explain the various components of computer with the help of block diagram.Ripunjay Tiwari
Ans. Fig. 1.5 shows the block diagram representation of a computer system. The solid lines are used to indicate the flow of instructions and data, and the dotted lines represent the control exercised by the control unit. It displays the five major building blocks or functional units of a digital computer system. These are-
(i) Input Unit – Input unit is responsible for entering any data. Data and instructions must enter the computer system before any computation performed on the supplies data. Data and instructions enter input units in forms that depend upon the particular device used. For example, data is entered from a keyboard.
All input devices must provide a computer with data, that are transformed into the binary codes that the primary memory of a computer is designed to accept. This transformation is accomplished by units called input interfaces.
There are some functions which are performed by an input unit.
- It accepts the instructions and data from the outside.
- It converts these instructions and data in computer acceptable form.
- It supplies the converted instructions and data to the computer system for further processing.
(ii) Output Unit – This unit is responsible for supplying information and results of computation to the outside world. The job of an output unit is just the reverse of that of an input unit. As computers work with binary code, the results produced are also in the binary form. Hence, results must be converted to human readable form before supplying the results to the outside world. Output unit converts in into human acceptable (readable) form.
There are some function which are performed by output unit.
- It accepts the results in binary form that are produced by the computer.
- It converts binary result into human acceptable form.
- It supplies the converted result to the outside world (user).
(iii) Storage Unit – Storage unit is responsible for storing data into memory. Entered data and instructions must be stored into storage unit before the actual processing starts. Similarly, the result produced by the computer after processing starts. Similarly, the result produced by the computer after processing must also be kept somewhere inside the computer system before being passed on to the output units. Moreover, the intermediate results produced by the computer, must also be preserved for ongoing Function which are performed by storage unit are as follows-
- It holds input data and instruction for processing.
- Holds intermediate results of processing.
- Holds final results of processing, before these results are released to an output device.
Thus, the CPU makes use of the following memory subsystems for carrying out is processing operations-
(1) Main memory unit – The main memory is referred to as the internal memory of the computer. It is also known as Random Access Memory (RAM). It is a temporary storage medium that holds the data only for a short period of time. The data stored in the RAM gets erased, when the computer is switched off. The memory space of RAM is limited and therefore all the file and instructions cannot be stored in it. These files and instructions are normally stored in a different location known as secondary storage and are copied from there to the RAM before execution. This technique is referred to as swapping. The memory space available in RAM also affects the speed of a computer system. As a result, the computer system need not read the data from the secondary storage again and again, thus making the processing faster. The main memory is also responsible for holding intermediate data transferred between CPU and I/O devices.
(2) Cache Memory – It is a small, fast, and expensive memory that stores the copies of data that is needed to be accessed frequently from the main memory. The processor, before reading data from or writing data to the main memory, checks for the same data in the cache memory. If it finds the data in the cache memory the processor reads the data from or writes the data to the cache itself because its access time is much faster than the main memory. The cache memory is laced between CPU and the main memory of the computer system, as shown in fig.1.6 The transfer of data between the processor and the cache memory is bidirectional. The availability of data in the cache is known as cache hit. The capacity of a cache memory is measured on thebasis of cache hit