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BBA 1st

INTRODUCTION

In computing memory refers to the physical devices used to store programs (sequences of instructions) or data (e.g. program state information) on a temporary or permanent basis for use in a computer or other digital electronic device.

TYPES OF MEMORIES

PRIMARY OR MAIN MEMORY

Main memory is divided into two parts :

Random Access memory (RAM), should be better known as Read Write Memory (RWM).

Read Only Memory (ROM) .

RANDOM ACCESS MEMORY

(RAM)

A RAM memory chip is an integrated circuit (IC) made of millions of transistors and capacitors. In the most common form of computer memory, dynamic random access memory (DRAM), a transistor and a capacitor are combines to create a memory cell, which represents a single bit of data.

TYPES OF RAM

STATIC RAM

Semi conductor memory

Uses flip flop to store each bit of memory so does not need to be periodically refreshed

Fast and consumes low power

Expensive and has complex structure(6 transistors) so not used for high capacity applications

DYNAMIC RAM

Stores each bit of memory in capacitor in an intrgrated circuit

Real capacitors leak charge so capacitors need to be refreshed periodically

Simple structure (1 capacitor and 1 transistor per bit) so it has very high density

D RAM

READ ONLY MEMORY

(ROM)

New contents cannot be added

Used to store the instructions of routine type,permanent in nature and used to control or supervise the hardware

Read only memory (ROM)

TYPES OF ROM

PROGRAMMABLE READ ONLY MEMORY (PROM)

Programmed to record the information using a facility PROM – programmmer

Once the information is recorded it cannot be changed

TYPES OF ROM

ERASABLE PROGRAMMABLE READ ONLY MEMORY (EPROM)

Information can be erased and chip can be reprogrammed to record different information using PROM programmer

In formation is erased using UV radiations

It is of two types- Ultra Voilet Erasable Programmable Read Only Memory (UEPROM) and Electrically Alterable Programmable Read Only Memory (EAPROM)

ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM)

Memory is erased by electrical signals

Provides easy means to store temporary or permanent information in the form of ROM memory

Types of Rom

CACHE MEMORY

Faster and expensive than RAM

It improves the computer’s performance and is less than 512 KB

Processor can use it to store frequently accessed data and programs instructions

It is of two types – L1 / primary cache(inside microprocessor) and L2/ secondary cache(in the mother board or near the microprocessor)

CACHE MEMORY

SECONDARY MEMORY

It supplements the main memory. It is permanent memory.

Programs, data entered into the system, intermediate results and final results produced are stored in the secondary memory

SECONDARY MEMORY

CLASSIFICATION

MAGNETIC BASED STORAGE DEVICES

Prepared using using formatting

Data is recorded on disk in concentric circular bands calledtracks.

MAGNETIC TAPE

FLOPPY DISK

HARD DISK

OPTICAL STORAGE MEDIA

Stores large amount of data in some formats as much as the entire hard disk

Reads data by focusing a laser- generated beam of light on light on disc’s surface

CD- ROM discs

DVD- ROM discs

MEMORY HIERARCHY

Ranking of computer memory devices, with devices having the fastest access time at the top of hierarchy, and devices with slower access time but larger capacity and lower cost at lower levels

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