MAIN MEMORY / PRIMARY STORAGE

MAIN MEMORY / PRIMARY STORAGE

This is also called memory, primary storage, and internal memory or Random Access memory.  It refers to working storage.

Main memory

-       holds data for processing.

-       Holds instructions for processing the data

-       Holds data after it is processed.

The contents in the main memory are temporal, meaning that if you turn off the computer before saving your work, you will loose any your latest edits.

It is characterized by fast access to information, low capacity and high costs.

There are two types of main memory in use today: These are;

(a)      RAM (Random Access Memory):  This is the primary storage device.  It stores information as one is currently working on the computer.  A computer will be slow with little RAM.

Characteristics of RAM

➢    It can be changed removed or changed.

➢    It is volatile. If you have data in this memory and there is power failure, all your work will be lost.

To avoid this, you should always save your work on a permanent memory such as a hard disk, flash disk, diskette e.t.c..

(b)      ROM (Read Only Memory):  This contains instructions which are permanently recorded in the memory.  Its contents can be read but cannot be written during normal computer operations.

Characteristics of ROM

➢    It cannot be changed or deleted.

➢    Rom is non-volatile.  It stores information permanently.

(c)      Registers: These are high speed staging ideas that temporarily store data and instructions that will be used immediately by the CPU.   To process an instruction, the control unit of the CPU retrieves it from memory and places it in a register.

Differences between RAM and ROM

RAM	ROM
1. It is volatile 2. RAM is read and write. 3. RAM is temporal 4. RAM can be increased	1. It is non volatile 2. ROM is read only 3. ROM is permanent 4. ROM is normally not increasable.

 N.B

(a)   Volatile memory loses its contents when the computer is turned off.  Almost all RAM is volatile.

(b)   Non-volatile memory does not lose its contents even when the computers power is turned off.  Examples include ROM, Flash memory, SMOS

(c)    ROM (Read only Memory is an example of non-volatile memory.  ROM chips containing data, instructions or information which is recorded permanently by the manufacture are known as Firm ware

(d)   BIOS (Basic Input Output System) is a firmware that contains the computers start up instructions.

Variations of ROM chips include

            (i) Programmable Read only memory (PROM).  This is a type of ROM chip on

     which permanently items can be placed.

            (ii) Erasable Programmable Read only memory (EPROM). Or Electronically

     Erasable programmable read only memory (EEPROM) are Rom chips

     designed to be modified by the user.

(e)     BIOS Rom contains the Basic input out system .  It is a sequence of instructions that a computer follows to load the operating system and other files when the computer is turned on.

(f)     Flash Memory also known as Flash Rom or Flash Ram is a kind of non-volatile memory that can be erased electronically and reprogrammed.  It is used to store programs and data on personal computers.

(g)   CMOS (Complementary Metal Oxide Semiconductor).  This is used to store configurations about the computer which includes;

➢    The amount of memory

➢    Type of disk drives

➢    Current data and time.

➢    Keyboard and monitor

CMOS chips use battery power to retain information even when the computer is turned off.             Unlike Rom, information stored in cmos can be changed.  The cmos chip is updated when ever new components are installed.