Understand that machine code is expressed in binary and is specific to a…

The idea

Machine code is the set of binary instructions a processor executes directly. Each instruction is a pattern of bits, for example a sequence of 0s and 1s, so machine code is expressed in binary. Crucially, machine code is specific to a processor or family of processors: the same binary pattern can mean different things on different processor designs, and an instruction set is tied to a particular architecture. This is why a program compiled for one processor family will not necessarily run on another without recompilation. The examinable points are that machine code is binary and that it is processor-specific, not universal across all hardware.

What earns the marks

• Machine code is expressed in binary, using patterns of 0s and 1s.
• Machine code consists of instructions the processor executes directly.
• Machine code is specific to a particular processor or family of processors.
• The same binary instruction may not be valid or may mean something different on another processor architecture.
• Programs may need recompiling for a different processor family because machine code is not portable across all processors.

Common mistakes and how to put them right

• Saying machine code is written in a high-level language.

  Put it right by stating it is binary instructions for the processor.

• Claiming machine code runs on any processor unchanged.

  Put it right: It is specific to a processor or family of processors.

• Describing machine code as text mnemonics.

  Put it right: Mnemonics belong to assembly language, machine code is binary.

Exam tips

• Emphasise both facts: binary representation and processor specificity.
• Use the idea of an instruction set tied to an architecture to explain specificity.
• Link processor specificity to why code may need recompiling for different hardware.