A bus is a collection of wires through which data/signals are transmitted…

The idea

A bus is the shared pathway that lets parts of a computer exchange data and control signals. Picture the CPU, memory and input/output devices as separate rooms: the bus is the corridor of parallel wires linking them. Because the same wires are shared, only one transfer happens at a time, so the bus carries an address identifying where data should go, the data itself, and control signals such as read or write. The key idea is that a bus is a collection of wires carrying data or signals between components, not a single device and not the processor itself. In a multiple-choice question, decide whether an option describes a set of connecting wires moving information between components; reject options describing storage, processing or a single wire carrying power only.

What earns the marks

• A bus is a collection of wires, not a single wire and not a processing unit.
• Its function is to transmit data or signals from one component to another.
• The components involved are separate parts of the system, such as the CPU, memory and input/output devices.
• The bus is shared, so transfers between components use the same set of wires.
• An option describing storage or processing rather than transmission between components is incorrect.

Common mistakes and how to put them right

• Thinking a bus is a single wire.

  Put it right by stressing it is a collection of wires forming a pathway.

• Confusing the bus with the CPU or with memory.

  Put it right by saying the bus connects components rather than performing processing or storage.

• Assuming the bus only carries data.

  Put it right by noting it also carries signals such as addresses and control information between components.

Exam tips

• Read each option and ask whether it describes wires carrying data or signals between components.
• Eliminate options that describe a component doing processing or storage rather than a connection.
• Check the option mentions transmission from one component to another, not just internal operation of one part.