2.3

Assembly language

2.3.1 Instruction set

A microprocessor can only act upon instructions which are specified in its instruction set. The instruction set consists of a series of hexadecimal codes, or opcodes, which are recognisable to the instruction decoder within the CPU. Each series of microprocessor has a unique instruction set, although many instructions are so common that they are found with only minor modifications in all microprocessors. In the 8086 CPU, instructions are 1 to 6 bytes long.

Some common classes of operations for which instructions are usually provided are:

• Data movement

• Integer and floating-point arithmetic

• Logical operations

• Shift and rotation of bits

• Bit manipulation

• Program control (branching)

A sequence ...

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