5.3 - The Processor Instruction Set

Question 1

What is an instruction set?

Answer 1

Describe the commands a processor can perform

Question 2

What a different toe of instruction types are there?

Answer 2

Data transfer: LDA, STR
Arithmetic operations: ADD, SUB
Comparison operations: CMP
Logical operations: AND, OR, NOT
Branch - conditional/unconditional
Shift operations: left/right bit shifts

Question 3

What is machine code?

Answer 3

Only language the processor can understand
Combinations of 0’s and 1’s

Question 4

What is the opcode (operation code)?

Answer 4

First few bits, it includes:
- the actual command the processor needs to carry out (ADD, SUB)
- the addressing mode

Question 5

What is the addressing mode?

Answer 5

Specifies whether the operand is the actual data, the memory address where the data is held, or a register

Question 6

What is the operand?

Answer 6

One or more items of data (values, memory addresses or registers) that are to be used in the instruction

Question 7

What decides the number of bits allocated for the opcode and operand?

Answer 7

Varies depending on the processor
Changes with word length

Question 8

What is immediate addressing?

Answer 8

When the operand is the actual value to be used in the instruction

Question 9

What is direct addressing?

Answer 9

The operand in this case is the address of the location in memory of the data to be used