x86 Assembly/X86 Instructions

These pages will discuss, in detail, the different instructions available in the basic x86 instruction set. For ease, and to decrease the page size, the different instructions will be broken up into groups, and discussed individually.

• Data Transfer Instructions
• Control Flow Instructions
• Arithmetic Instructions
• Logic Instructions
• Shift and Rotate Instructions
• Other Instructions
• x86 Interrupts

For more info, see the resources section.

Conventions

The following template will be used for instructions that take no operands:

Instr

The following template will be used for instructions that take 1 operand:

Instr arg

The following template will be used for instructions that take 2 operands. Notice how the format of the instruction is different for different assemblers.

Instr src, dest	GAS Syntax
Instr dest, src	Intel Syntax

The following template will be used for instructions that take 3 operands. Notice how the format of the instruction is different for different assemblers.

Instr aux, src, dest	GAS Syntax
Instr dest, src, aux	Intel Syntax

Suffixes

Some instructions, especially when built for non-Windows platforms (i.e. Unix, Linux, etc.), require the use of suffixes to specify the size of the data which will be the subject of the operation. Some possible suffixes are:

• b (byte) = 8 bits.
• w (word) = 16 bits.
• l (long) = 32 bits.
• q (quad) = 64 bits.

An example of the usage with the mov instruction on a 32-bit architecture, GAS syntax:

movl $0x000F, %eax  # Store the value F into the eax register

On Intel Syntax you don't have to use the suffix. Based on the register name and the used immediate value the compiler knows which data size to use.

MOV EAX, 0x000F