Primary Storage and Secondary Storage Devices Chapter 3 October 6 University Primary Storage and Secondary Storage Devices Chapter 3 Prof. Dr/ Moussa Ibrahim Moussa Dean of Faculty of Information Systems and Computer Science

Learning Objectives Name several general properties of storage systems. Describe how magnetic disk systems (such as hard drives) work. Discuss the various types of optical disc systems available and how they differ from each other and from magnetic systems.

Identify some flash-memory-based storage devices and media and explain how they are used today. List at least three other types of storage systems. Summarize the storage alternatives for a PC, including which storage systems should be included on a typical PC and for what applications other storage systems are appropriate.

Storage Unit: A storage unit is that part of the computer system which is used to store the data and instructions to be processed.

There are two types of storage: 1) Primary storage 2) Secondary storage.

1) Primary storage Primary storage is characterized by:- faster access time less storage capacity higher costs The primary storage is volatile Primary storage is also called Random Access Memory (RAM)

ROM : * ROM: ROM is Read Only Memory. *ROM are not lost even when the power is turned off * This memory is non-volatile.

PROM PROM: PROM is Programmable Read Only Memory. PROM is non volatile .

EPROM It is possible to erase the data which has been previously stored on an EPROM and write new data onto the chip.

Cache Memory The Cache Memory is a very special type of high speed memory cannot be accessed by the user. The main function of this cache memory is to make the programs and data available to the CPU very fast.

Registers Registers are used to retain information temporarily Some of the common registers are: - Memory Address Register (MAR) - Memory Buffer Register (MBR) - Program Control Register - Instruction Register

Program Control Register Instruction Register

2) Secondary storage.

Information stored on secondary storage devices can be accessed in two ways:  Sequential Access  Direct Access

 Sequential Access a) Punch Paper Tape: b) Magnetic Tape:

 Direct Access a) Magnetic Disk: b) Floppy Disks :

THANKS