Assembly

  • Assembly is one level up from machine code and provides a more human-friendly abstraction layer

  • An assembly instruction is a mneumonic that comprises an “op code” plus operands

  • It is translated back to machine code by an assembler for the computer to execute.

Example instruction

We can translate the machine instruction e3a07004 into the assembly instruction mov r7, #4. This translates to: move the value number 4 to the register r7.

Assemblers

Although assembly is useful for humans, computers still work at the level of machine code. Therefore you need an assembler to translate the assembly code to machine code. An assembly language text file is fed into an assembler and a binary object file containing machine code is returned.

A disassembler does the opposite: translate machine code into assembly.

Relation to instruction set architectures

  • the ISA defines the hardware capabilities and the instructions that can be run on the hardware
  • machine code is a binary representation of these instructions and can be directly executed by the CPU
  • humans use an assembly language version of the machine code which is then translated back to machine code for the computer to execute.

Hexadecimal number system, Instruction Set Architectures, CPU architecture

logo