Functional Units of Computer

Every functional system incorporates some functional parts that constitute a consumable product. Similarly, there are some functional units of the computer that constitute in producing logical outputs.

Five basic functional units of a computer are i.e. input unit, a processing unit (Arithmetic and logic), a memory to store final or intermediate results, a controlling unit that coordinates functions of every unit, and finally an output unit. In this article, we will discuss all the functional units of the computer.

Functional Unit of Computer

The functional units of a computer i.e. input unit, arithmetic and logic unit, memory, control unit, output unit all are connected with the interconnection network that helps them in exchanging the information as you can see in the image below. Now, let us explore each functional unit separately.

Functional Unit of Computer

Input Unit

The input to the computer is either a data or instruction, that guides the arithmetic and logic unit about what operations have to be performed and also controls the movement of data between the computer and its I/O devices.

Now, the input i.e. data or instruction are accepted with the help of input units such as a keyboard, mouse, touchpad, joystick, and trackball. The most familiar device that we use to accept input is the ‘keyboard’ and ‘mouse’. All of these input devices are graphic input devices and you can see their effect on the display unit.

Whenever you strike any key on the keyboard it gets converts to the binary code and is handed over to the processor which would interpret the code and perform the appropriate action.

For audio and video input, microphones and cameras are used respectively. Now a day, the internet can also be used to issue an input to a computer from other computers or databases.

Memory Unit

A memory unit is required to store the programs that have the set of instructions that instructs Arithmetic and logic unit which operation has to be performed. It also stores the data associated with the program. The memory can further be classified into three types:

  1. Primary Memory
    Primary memory is also known as the main memory or the random-access memory (RAM). It is the fastest accessible memory of the computer. If a program has to be executed it first needs to be placed in the primary memory. Then the instructions of the program are fetched one at a time by the processor for execution.
    The memory is organized in such a way that in one basic operation, one-word can be retrieved from the memory or one word can be stored to the memory. A word length could be 16, 32, or 64 bits.
    The primary memory is expensive as well as faster. But primary memory is volatile in nature it does not retain its content when the power gets off.
  1. Secondary Memory
    Secondary memory is the hard disk of your system, it also includes flash drive, optical disks, magnetic disk. The secondary memory is slower and less expensive as compared to primary memory. It doesn’t lose its contents even if the supply of power gets off.
    We require secondary memory to store a large volume of data or program permanently or the data that is less likely to be retrieved.
  1. Cache Memory
    Cache memory can be accessed much faster as compared to primary memory and it is even smaller in size. It is stored with the data that is required frequently by the processor.
    As we know the program to be executed and the data associated with it is brought to the primary memory and the processor fetches the program instructions from there. The process also places a copy of the instructions and associated data in the cache memory.
    Now, the instructions that are required to be executed repeatedly such as loops are retrieved from the cache memory to improve the execution rate.

Arithmetic Logic Unit

All the arithmetic operations are performed by the arithmetic logic unit of the processors. Arithmetic operations such as addition, subtraction, division, multiplication, comparison between the numbers, etc.

The ALU unit performs the operations present in the instruction and stores the result into the memory. It also stores the intermediate results of the operation in the registers.

The arithmetic operation is performed on the operands. The operands are placed into the registers which store one word at a time which is sufficient for an operand. Retrieval of the data form registers is even faster than the cache memory.

Output Unit

A computer is a functional unit and as it has an input unit to accept the input it also has the output unit to provide the generated output by the system. The most familiar device used to output a result is a printer.

A display screen is also an output unit as it displays the generated result, but it also displays the input provided to the system. That’s why the display screen is termed as the ‘I/O unit’ because of its dual function.

Control Unit

The functions of input, ALU, memory, and output unit must be coordinated so that everything goes in sequence i.e. the processor accepts input, place it in memory, processes the stored input, and generates output. This entire sequence is coordinate by the control unit.

In this way, the functional units of computers cooperate to generate useful output. We have discussed each of the functional units of the computer in brief and understood their functional behaviour.

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