Instruction set
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What is an instruction set?
The set of machine code instructions that a specific processor can understand/execute
When can two different type of processors be compatible?
If they operate on the same instructions, use the same machine code
What are the two parts that make up a machine code instruction?
The opcode and the operand
What does the opcode state?
The opcode is the instruction to perform.
What does the operand state?
The operand is the value or memory address to be used
What are the two addressing modes?
Immediate and Direct Addressing
What is immediate addressing?
• The data in the operand is immediately available for use as it represents a value e.g. 6 or 187 • This is a very fast addressing mode
What is direct addressing?
• The data in the operand refers to a memory location - Disadvantage is that code cannot be relocated
What is branching?
Branching is used for conditional statements or unconditional statements
What is a label?
A sequence of characters that identify a location in the source code
In operations what does the # symbol indicate
The # indicates that the operand is a number, uses immediate addression No # indicates that the operand is a memory address.
What does the halt operation do?
It terminates the program operation.
How many bits may each machine code instruction occupy up to? (if it provides a diagram)
32 bits, usually 6 slots if there are more or less slots just count up for example if there are 5 slots do - 1 2 4 8 16, 16 is the 5th slot
How many different opcodes can be represented with 4 bits
2^4 = 16 different opcodes