Introduction to

Introduction To Computer Science
40
The Control Unit
The control unit is responsible for managing the process of moving data and program into and 
out of memory. It is also responsible for carrying out (executing) program instructions - one at a 
time. This includes the idea of a ‘register’ to hold intermediate computational values. 
Peripheral Devices
A peripheral device is generally defined as any device such as mouse or keyboard connected 
to a computer system to add functionality[4]. 
Types of Peripheral Devices
Types of peripheral devices fall into three general categories, they are:
• Input devices: such as a mouse and a keyboard
• Output devices: such as a monitor and a printer
• Secondary Storage devices: such as a hard drive or flash drive.
Devices like CD-ROM fall into more than one category in that users can use a CD-ROM to read 
data or music (input) as well as to write data to a CD (output).
Peripheral devices can be further divided into external or internal. For example, a printer is an 
external device that you connect with the computer using a cable, while an optical disc drive is 
typically located inside the computer case. 
For a desktop computer, a keyboard and a monitor are considered peripherals in that you can 
easily connect and disconnect them as needed. For a laptop computer, these components are 
built into the computer system and can’t be easily removed.
Activity Conclusion
The von Neumann architecture, also known as the von Neumann model and Princeton 
architecture, is the first model to represent the stored-program concept that has fundamentally 
changed computing. The following are characteristics of the Von Neumann Architecture:
√ It uses a single processor.
√ It uses one memory for both instructions and data.
√ It cannot distinguish between data and instructions in a memory location
√ It distinguishes between data and instructions only because of the location of a