Internal components

Question 1

What are the main components of a computer system?

Answer 1

Processor
Main memory
Input/output (I/O) controllers

Question 2

What is a processor?

Answer 2

Executes program instructions (machine code)

Question 3

What is main memory?

Answer 3

Memory that can be directly accessed by the processor

Question 4

What are the two types of main memory?

Answer 4

RAM, which is the working memory that is used by the processor during the fetch-decode-execute cycle
ROM, which is used in the boot process for the computer system

Question 5

What is the system bus made up of?

Answer 5

an address bus
a data bus, and
a control bus

Question 6

What is the purpose of the system bus?

Answer 6

The system bus is used to connect the processor (CPU), main memory, and the I/O controllers. The following diagram illustrates an abstract model of the connections.

Question 7

What is the purpose of the data bus?

Answer 7

The data bus is used to transfer data and instructions. The data bus is bidirectional, i.e. it allows a two-way connection between internal components of the system — allowing values to be written to or read from a location.

Data is transferred to and from the processor
Data is transferred to and from main memory
Data is transferred to and from the I/O controllers
Instructions are carried from main memory into the processor (to be decoded and executed)

Question 8

What is the purpose of the address bus?

Answer 8

The address bus is used to specify the address of a memory location to either read (i.e. load) data from or write (i.e. store) data to that memory location.

There is a one-way connection from the processor to the address bus and a one-way connection from the address bus to the main memory and to the I/O controllers. This is because the address bus is a unidirectional bus, which allows the processor to establish a connection with an addressable ‘unit’, whether it’s a memory location or an I/O controller.

Question 9

What is the purpose of the control bus?

Answer 9

The control bus is used to send control signals that manage and orchestrate the operations that take place inside a computer system. This includes exchanging status signals between the components of the computer system, and transmitting clock signals required for the coordination of operations. For example, a control signal can be used to:

Request communication between two units
Acknowledge a communication request
Specify the type of data that is being transferred via the other buses (i.e. data values, instructions, or addresses)
Synchronise the communication between the components using the clock pulses
The control bus is bidirectional, i.e. there are two-way connections between the components that the control bus connects.