Explain the instruction format of basic computer. Write down symbolic representation for FETCH routine.

The instruction format of a basic computer is typically divided into three parts: the operation code (opcode), the indirect address bit, and the address.

1. Operation Code (Opcode): This is the first part of the instruction format. It specifies the operation to be performed, such as ADD, SUB, MUL, DIV, LOAD, STORE, etc.

2. Indirect Address Bit: This is the second part of the instruction format. It is used to specify whether the given address is direct or indirect. If the indirect address bit is 0, the address is direct. If it is 1, the address is indirect.

3. Address: This is the third part of the instruction format. It specifies the memory address of the operand.

The symbolic representation for the FETCH routine can be written as follows:

1. PC out, MAR in: This transfers the content of the Program Counter (PC) to the Memory Address Register (MAR).

2. Read Memory: This reads the content of the memory location specified by the MAR into the Memory Buffer Register (MBR).

3. MBR out, IR in: This transfers the content of the MBR to the Instruction Register (IR).

4. PC increment: This increments the PC by 1 to point to the next instruction.

So, the symbolic representation for the FETCH routine can be written as:

PC out, MAR in
Read Memory
MBR out, IR in
PC increment