Understand the term ‘processor instruction set’ and know that an instruction set is processor specific.
The instruction set of a typical computer includes the following types of instructions:
- Data transfer such as
LOADandSTORE - Arithmetic operations such as
ADDandSUBTRACT - Comparison operators such as equal, greater than, less than
- Logical operations
AND,OR,NOTandXOR - Branching conditional and unconditional
- Logical shift bits left or right
Know that instructions consist of an opcode and one or more operands (value, memory address or register).
Opcode
- The part of a machine code instruction, that represents a basic machine operation.
Operand
- The part of the machine code instruction that contains an item of binary data or address in which the binary data is stored
- Operands can have immediate and direct addressing modes
- Immediate – actual datum value in operand is operated on.
e.g. #5 means the number 5 is operated on - Direct - holds the memory address of the datum value to be operated on.
e.g. 5 means memory address 5 is operated on
- Immediate – actual datum value in operand is operated on.
Students will not be expected to define opcode, only interpret opcodes in the given context of a question
- Logic shift can be used for multiplication/division by any power of 2.