Our TopicsDefine the terms- Instruction, Micro-

operation, Instruction set, Instruction set completeness, Instruction code, Operation code ;

Instruction format ; Instruction types ;Direct and indirect addressing with Figure.

It means set of Instruction. Minimum set of instructruction should be 25 . Instruction

Set

The set of instruction are said to be complete if the user can construct any function that is known to be computable .

Instruction Set Completeness

An Instruction code is a group of bits that instructs the computer to perform a specific operation .

Instruction Code

An Operation Code is a group of bits that define operation ,such as addition,substraction,multiplication etc.When this operation code is decoded in the control unit the computer issues control signal to read an operand from memory .

Operation Code

The simplest way to organize a computer is to have one processor register and an instruction code format with two parts. The first part specifies the operation to be performed and the second specifies an address . 

Types Of Instruction

The basic computer has three instruction code formats.Each format has 16 bits. The operation code part of the instruction contains 3 bits,the remaining of the remaining 13 bits depends on the operation code encountered.

When the bits in the second part of the instruction designate an address of a memory word in which the address of the operand is found, it is called Indirect Address. A indirect address instruction is shown in the following figure :

Direct Addressin

g

When the second part of an instruction code specifies an operand, the instruction is said to have a direct address.A direct address instruction is shown in the following figure :