Instruction Set
An instruction set defines the operations that a processor can perform. These operations range from simple arithmetic computations to complex memory manipulations. Each instruction is represented by a unique binary pattern, known as opcode, which is decoded by the processor to execute the corresponding operation.
Types of Instructions
The instruction set of an assembly language typically comprises various types of instructions. Here are some common categories.
1 Data Movement Instructions
These instructions facilitate the transfer of data between memory locations and registers. Examples include MOV (mov), which copies data from one location to another, and LOAD/STORE instructions, which transfer data between memory and registers.
2 Arithmetic and Logic Instructions
Assembly language provides instructions for performing arithmetic operations (such as addition, subtraction, multiplication, and division) and logical operations (such as AND, OR, XOR, and NOT) on binary data. These instructions are essential for mathematical computations and bitwise manipulations.
3 Control Flow Instructions
Control flow instructions determine the flow of program execution. These include conditional branches (e.g., JMP, JZ, JNZ) for making decisions based on specific conditions, unconditional branches (e.g., JMP) and subroutine call/return instructions (e.g., CALL, RET) for implementing procedures and subroutines.
Understanding Operand Formats
Each instruction in the assembly language operates on one or more operands, which represent the data involved in the operation. Operand formats vary depending on the instruction and the architecture.
Common Operand formats include:
- Immediate: The operand is a constant value specified directly in the instruction.
- Register: The operand refers to a processor register.
- Memory Address: The operand specifies a memory address where the data is located.
- Register-Memory: The instruction involves both a register and a memory operand.