Fundamental OF Hardware And Software- Primary Storage

Seite 1

Fundamentals

of Hardware and Software

MEMORY STORAGE

The

computer is able to store information for future use. This proves to be very important especially

when it comes down to the fact where you need to transfer information from one

place to another or need to update or finish your work at a later date or

time. The computer's memory stores

information the computer is using at the time.

Its capacity is limited and data and processing results are lost when

the computer is switched off or power is disrupted from the computer. If data, programs and processing results are

to be preserved for repeated and permanent use, additional storage capacity

must be available. Secondary Storage

Devices serves this purpose. Secondary

Storage is still slower than Primary Storage in that it takes a longer time to

access information stored but it is less expensive that Primary Storage.

MAIN MEMORY

This is the memory area in which all

programs and data are stored while the computer is executing programs. Main Memory is very important to a computer

because it can be written to and read from at high speed. Main Memory is also referred to as Primary

Memory/Primary Storage/Immediate Access Storage. Primary Storage may also be defined as

the component of the computer that temporarily stores program instructions and

data being used.

Functions of Main Memory

1. Stores program instructions prior

to execution

2. Stores the data which can be

immediately processed by the program instructions

3. Stores information temporarily

after processing is complete

TYPES OF MEMORY

RANDOM ACCESS MEMORY (RAM)

This is a type of memory that allows information to be

written to and read from by the CPU. RAM stores information temporarily so that it

is directly and speedily available to the Microprocessor. It is also a memory storage device (chip)

used for short-term storage of data and program instructions. Random Access Memory is constantly being

refreshed with electrical impulses.

Random Access Memory is said therefore to be volatile (information

is stored depending on electrical power). The contents of Random Access Memory are

temporarily stored and are lost when electrical power is disrupted or when the

computer is turned off. All programs and

data must be transferred to RAM from an input device (such as a keyboard) or

from a secondary storage device (such as Magnetic Disks) before programs can be

executed and data can be processed. Why

is it called Random Access Memory? The term Random Access doesn’t

imply that the memory stores data randomly!

A better term for RAM would be Direct

Access Memory. In RAM, each

memory location has an address, just like a post office box. Using this address, called a Memory

Address, the CPU can store and retrieve data by going directly

to a single location in memory.

Fig. 1 In RAM, each memory location has an address

like a P.O. Box. Using the Memory

Address instructions can be stored and retrieved directly.

1001

1002

1003

1004

1005

1006

1007

1008

1009

DATA

1010

READ ONLY MEMORY (ROM)

If everything in RAM is erased when the power is turned off from the

computer, how does the computer

maintains important instructions?

The answer – ROM.

The

instructions to start the computer are stored in ROM Chips, which are

non-volatile. This is a type of memory

that allows information to be read from and cannot be written to

(changed or altered) by the user.

It

is also a memory storage device (chip) used to store important data and program

instructions permanently. Read Only

Memory is said to be static or non-volatile (information storage does not

depend on the availability of electricity). This means that what is stored in Read Only

Memory is not lost when the electrical power to the computer is disrupted or

when the computer is turned off. Read

Only Memory can be used to store programs that will be required to perform

specialized routine functions. Example,

sometimes the Operating System which is a program which controls the operations

of the computer and its resources, are stored into Read Only Memory so that

every time the computer is switched on, the computer will check and load the

Operating System Program into Random Access Memory from Read Only Memory. What is stored in this memory may not be

destroyed if someone tries to write over/to erase/to modify (change) what is

stored. The information stored in Read

Only Memory is "burnt in" by the manufacturer and the user can

only read and use the information and program instructions stored. The data and program instructions stored on

Read only Memory Chips is stored in a way so that it cannot be changed by the

user hence it is called Read Only Memory. So as to allow for upgrades to ROM, most

computers use Flash Memory, or Flash BIOS, PROM and EPROM.

In

Personal Computers (PCs), ROM is used to store the computer’s Basic

Input/Output System (BIOS).

When you start your computer (also called Booting), the

BIOS execute a Boot Sequence. In

the Boot Sequence, the BIOS conducts various Power-On Self-Tests (POST),

including memory tests, configuring the system’s hardware, and locating the

Disk Storage containing the Boot Sector.

The Boot Sector contains the computer’s basic functions for start up

operations.

Functions of Read Only Memory

1.

To store start-up instructions for the computer permanently

2.

To store program instructions/machine instructions the computer will

need to use to control its operations

THE ROLE OF READ ONLY MEMORY Vs. RANDOM ACCESS MEMORY

It is important to note that every computer must

have both Read Only Memory and Random Access Memory. One needs to understand that the computer

requires a memory to store programs and instructions that are currently in use

by the CPU.

This type of memory is known

as Random Access Memory. However, the

computer also has to be comprised of a memory to store program instructions,

programs and data that are essential to the running of the computer. This type of memory as known as Read Only

Memory.

NB A

computer does not have to search its entire memory each time it needs to find

data because

the CPU stores and retrieves each

piece of data (information) using MEMORY ADDRESSES.

TERMS ASSOCIATED WITH MEMORY

CACHE Memory

RAM is fast but isn’t fast enough to support the processing speeds of

today’s super fast microprocessors such as Pentium II. To enable these microprocessors to operate at

such high speeds, today’s computer designers uses CACHE Memory. This memory is much faster than RAM, but it’s

also more expensive. CACHE Memory helps to improve the computer system’s

overall performance. The

microprocessor can use this memory to store frequently and recently accessed

instructions, programs and data.

Bistable Device This is a device, which exists in two (2)

discrete states. Example, the Binary

System exists in only zero and 1.

Programmable Read Only Memory

(PROM) This

is a type of Read Only Memory where the user can only read the

program instructions stored and not alter (change/modify) its contents. PROM is used to program instructions

into Read Only Memory. Also, PROM

is a form of ROM, which is manufactured without program instructions

stored on it. Program instructions can

be read into PROM and therefore allowing it to become Read Only Memory. PROM is a variation (type) of ROM into which

you, the user, can load read only programs and data. Generally, once a program is loaded into

PROM, it is seldom, if ever, changed. It

may also be seen as a blank memory chip on which you can place data items

permanently.

Erasable Programmable Read Only

Memory (EPROM)

This is a type of Read Only Memory that allows the user to erase or update PROM. They are used in robots and other devices in

which the program instructions stored will only be changed or may only be

changed periodically.

Write Once Read Many (WORM)

Program A

program that erases data and/or program instructions from the computer system's

memory. It is usually used with

malicious or purposeful intent to destroy and/or erase information and program

instructions stored on a computer.

BIT This is a binary digit. Examples of binary digits are 0 or 1. A bit may also be described as the smallest

unit of data storage.

BYTE This is a group of 8 adjacent bits joined

to represent a character.

KILOBYTE (KB) This is 1024 bytes or little

over 1000 bytes of storage capacity.

MEGABYTE (MB) A Megabyte is one million (1,

048,576 – 1024 x 1024) bytes of storage capacity.

GIGABYTE (GB) A Gigabyte is one billion bytes

of storage capacity.

TERABYTE (TB) A Terabyte is one trillion bytes

of storage capacity.

WORD An established number of bits that the

computer handles as one unit.

ADDRESS Name, numeral or label that designates

(tells) a particular location in memory.

LOCATION This is where data is stored.

WORD SIZE This is the number of bits in each word.

MEMORY LOCATION/ADDRESS This is an address in memory.

BUFFER This is an intermediate memory that

temporarily stores data that is being taken from Main Memory and sent to an

output device. Buffer might also be

described as a special area of memory from

which data can be accessed.

REGISTERS A high-speed storage area built directly

into the ALU and is used to hold

instructions and data currently being used by the CPU. It may also be described as a high-speed

storage area in which data pertaining to the execution of a particular

instruction is stored.

CMOS - Complementary Metal Oxide Semiconductor A type of

semiconductor often used in computers for batter-powered circuits that store

the date, time and system configuration information.

Additional

Content: Synchronous Dynamic Random Access Memory

(SDRAM), Single In-line Memory Module (SIMM), Dual In-line Memory Module (DIMM),

Flash Memory and Cache.

Memory Bit

Internal Storage

Volatile Memory - SDRAM,

Rambus DRAM, Cache and Registers

Nonvolatile Memory - ROM, ROM and Flash Memory

64 – 128 MB

(Minimum)

128 – 256 MB (Minimum)

512 and up

(Minimum)

USE

Home and business users managing personal finances, using

standard application software such as Word Processing; using educational or

entertainment CD-ROMs, communicating with others on the Web.

Users requiring more advanced multimedia capabilities;

running, number intensive accounting, financial or spreadsheet programs;

using voice recognition; working with videos, music and digital imaging;

creating Web sites; participating in video conferences; playing Internet

guides.

Power users creating professional Web sites; running

sophisticated CAD, 3 D design, or graphics intensive software.

Fig. 2 RAM Guidelines

Processor

600 – 750 MHz Celeron Processor

866 MHz – 933 MHz Pentium 4 Processor

1.2 GHz – 1.5 GHz Pentium 4 Processor

Memory

64 – 128 MB RAM

128 – 256 MB RAM

Greater than256 MB RAM

Fig. 3 Determining how much RAM you need depends on

the applications you intend to run on your computer. Advertisements for computers normally list

the type of processor, the speed of the computer

measured in MHz or GHz, as well as the amount of RAM installed.

Assignment to do: Collect several advertisements for

computers that are being sold and determine whether the size of memory stated

is sufficient for the given speed of the CPU.

Make your recommendations.