1.1 The Central Processing Unit

The CPU (Central Processing Unit) is the most important component in any computer system.


The CPU processes data and instructions by constantly repeating the fetch - decode - execute cycle.


CPU Components

Directs the flow of data and information into the CPU.

Also controls the other parts of the CPU.

Stands for ‘Arithmetic Logic Unit’. It performs simple calculations and compares data.

The registers are temporary storage spaces for data and  instructions inside the CPU. The registers are used during the FDE cycle.


Computer Architecture

The way a computer is designed and laid out is known as its architecture (like how a house is planned).

There are two main types of computer architecture. Von Neumann, which is used most often, and Harvard.

Von Neumann Architecture

Von Neumann architecture stores both instructions and data in memory, a revolutionary idea when it was created in 1945.

Being able to store programs in memory allows computers to be re-programmed for other tasks - this allows us to multi-task and run several programs at the same time. Data input and output is another key feature of this architecture.

Harvard Architecture

Harvard architecture has separate storage areas and buses (data circuits) for instructions (Program memory) and for data (Data Memory).

The control unit is the most important component of Harvard architecture. 

Questo's Corner

The CPU:

Describe the role of each CPU component:

a. Control Unit

b. Arithmetic Logic Unit

c. Registers


a. Which type of architecture do most modern computers use?

b. What is the most important feature of Von Neumann architecture?

c. How is Harvard architecture different than Von Neumann?

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