What is computer instruction?

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Computer instructions are a group of machine language instructions and are executed by a specific computer processor.

Whatever instruction we give to the computer will work on its basis.

There are fields in an instruction, these fields are the following: –

• operation code (Opcode) field –

This specifies the operation to be performed.

• Address field –

It stores the location of the operand.

• mode field –

This field specifies how operands will be detected.

A basic computer has three instruction code formats which are given below: –

1. memory – reference instruction                                  

2. register – reference instruction

3. input-output instruction

memory- reference instruction

In this instruction, a memory of 12 bits is used to specify the address and a bit memory is used to specify the addressing mode.

register -reference instruction

These instructions are presented in opcode 111 (with 0 in the leftmost bit).

The register reference instruction is specified in the AC (accumulator) register operation.

input-output instruction

It is presented in operation code 111 (with 1 in the leftmost bit). And the remaining 12 bits are used to specify the type of input-output operation.


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