Describe a general-purpose computer system

The computer system

The computer system is a programmable electronic device that processes data, following a set

of instructions to produce information which it can output or store for future use. A computer

system has two major components.

Hardware (Click for details)

Software (Click for details)

other components of the computer system.

Data - Facts like first and last name, subject, gender, and grade. Data should be the broken

down into the small piece of individual fact so that it can be easily stored.

Information - Data that has been interpreted into a useful format. For example, from the data

on subject, we should be able to count how many subjects they are, how many males and

females, or create a report with the student's first and last name, subjects and grades.

A computer has four functions: Input, Processing, Output and Storage. The data stored can

also be used as input to another program or for more processing thus forming a cycle.

Every computer must be able to do

four things

1. Accept Input

2. Process the Input

3. Produce an appropriate

Output

4. Store the results of Processing

Types of computers

Microcomputers

These are the smallest, least powerful, affordable computer system available. Microcomputers

can be broken down into three smaller categories.

Desktops (PCs)

Laptops

Palmtops

Desktops/Personal Computers (pc)

These are sometimes called microcomputers

and they are the most common types of

computers. They are available in many

different styles depending on the

manufacturer.

The PC consists of a system unit, a mouse,

keyboard and monitor.

The PC has all the functional elements of

larger computer and is able to run a wide

array of software that can be installed to it.

Laptops

This is a smaller, easily portable version of a PC,

consisting of:

a flat liquid crystal display (LCD) coloured

screen and weighing approximately four

kilograms;

a touch sensitive area which serves as a mouse;

a rechargeable battery;

built in speakers;

CD/DVD drive

Modern features

Finger print scanner

built in microphone;

built in webcam;

card reader

built-in antenna for (Wireless communication)

Notebooks and sub-notebooks are the two general types

of laptops and have the same functionality of a regular

laptop.

Tablet pc

This is a computer that resembles a notebook except

that is does not have a keyboard attached to it. Tablet

PCs have wide touch screen or digitising tablet that can

be used to operate it by the touch of a finger or a special

pen called a stylus.

Minicomputers

These have now become

outdated and are

seldom used. Their storage

capacity, cost and processing

power falls between a

personal computer and a

mainframe computer. These

computers were originally

designed to facilitate the

processing of multiple users

simultaneously. This was

done by allowing users to

share access to central

hardware through stations

called terminals.

A terminal consists of

keyboard, display screen and

wires that connect the

keyboard and display screen

to the system unit.

Mainframes

These are very large, powerful and expensive

computers. Mainframes offer much greater

storage capacity and processing than

minicomputers and PCs. These computers

will allow more than 1000 users

simultaneously access and use the system.

These computers are most often found in

large organisations such as:

Banks

Government agencies

insurance companies

large corporations

Mainframe computers are useful for the

bulk data processing such as censuses;

industry/consumer statistics and;

Bank transaction processing.

Supercomputers

Supercomputers are the most powerful

computers in the world. Supercomputers are

dedicated mainframes that may be

specifically designed for tasks such as

performing complex and

repetitive calculations.

Two examples of the world’s fastest, largest

and most powerful supercomputers are:

California's Digital corporation's Intel

Itanium2 Tiger4

NEC's Earth Simulators

Embedded computers

These are computers that are used inside devices and are usually dedicated to specific

functions. Embedded computers may be connected to sensors (devices that detect

environmental changes) and actuators (hardware output devices that convert an electronic

control signal into physical action).

Explain the functions of the major hardware components

of a computer system

Hardware

Hardware refers to the physical components that make up a computer system. There are

particular hardware devices that are responsible for each of the following:

accepting input (Raw data or instructions);

processing the input;

outing the result of processing in a understandable format;

Store the result of processing.

The Data Processing

Cycle

Input Devices

An input device is any hardware device that sends data to the computer, without any input

devices, a computer would only be a display device and not allow users to interact with it, much

like a TV. Input devices can be placed into three general categories. There are four major

categories of input devices: Key devices, Point and draw, multimedia and source data

automation.

Keyboard Devices

Keyboard

Keypad

Point and draw

Mouse

Track ball

Joystick

Pen Inputs

Bio-metric systems

POS Pin entry Devices

Track Pad

Touch Screen

Digitiser Tablets

Multimedia Input Devices

MIDI keyboard

Microphone

Web Cam

Digital Camera

Gamepad

Electronic Whiteboard

Source data automation

Optical Character Reader (OCR)

Optical Mark Reader

Magnetic Ink Character Recognition (MICR)

Bar Code Reader

Remote Control

Censors

Scanner

Card Reader

Modem

RFID (radio frequency identification)

Output Devices

Any device that outputs information from a

computer is called, not surprisingly, an output

device. Since most information from a

computer is output in either a visual or auditory

format, the most common output devices are

the monitor and speakers. There are two types

of outputs that are generated by output

devices, Hard copy and Soft Copy. Examples of

Output devices are:

Visual Display units (VDU)

Projectors

Printers

Plotters

Touch Screen

Head Phones

Earphones

Speakers

Video Card (Graphics Card)

Virtual reality Headset

Modem

LEDs

Microfilm

Storage Devices

A storage device is a hardware device capable of holding information. There are two storage

devices used in computers; a primary storage device such as computer RAM and a secondary

storage device such as a computer hard drive. The secondary storage could be

a removable, internal, or external storage.

Primary Storage Devices

ROM

RAM

PROM

EPROM

EEPROM

Secondary Storage Devices

Floppy Disk

Hard drive

CDs (Optical Storage)

DVDs (Optical Storage)

Blu ray discs (Optical Storage)

Magnetic Tape

Tape Drives

Flash Memory

Processing

The CPU (Microprocessor/ Processor)

CPU is short for Central Processing Unit and

is the brain of the computer. It processes

every instruction. Any task that needs to be

executed is sent to the CPU.

The CPU is compose of two components, the

Arithmetic and logic Unit (ALU) which

performs arithmetic and logical

operations, and the Control Unit (CU) which

extracts instructions from memory and

decodes and executes them.

Outline the functions and uses of primary storage devices

Primary Storage Devices:

1. RAM 2. ROM 3. PROM 4. EPROM

Bistable Devices:

A bistable device is a device that can exist in one of two possible states, which could either be on

or off. Think of a key on a keyboard that is either down or up. A letter is either CAPS or not, a

light switch is either ON or OFF. These may help you understand the concept of BISTABLE.

Random-access memory (RAM):

RAM is a form of primary storage, it is volatile (remember that the data is lost when the

computer is turned off). RAM is stored on an integrated circuit shown above.

The purpose of RAM is that it allows quick access to this stored data. That means, if you are

working on a ten-page assignment, and you are at page 4, then if you scroll to page 9, the

processor will quickly access the information on page 9 from RAM and show it on the screen for

you with you realizing what is happening in the background. It may even swap the data on pea 4

and store it in RAM temporarily until you scroll up to that page again!

Read-only memory (ROM):

Computers contain a small amount of read-only memory that holds instructions for starting

up the computer. Unlike RAM, ROM data cannot be written to it. It is non-volatile which

means once you turn off the computer the information is still stored in it.

ROM is not only found in computers. Most devices with electronic components such as

microwaves, cell phones, videos contain ROM chips

There are various types of ROM. These include PROM and EPROM

Programmable Read-only memory (PROM):

PROM is a memory chip on which data can be written only once. Once a program has been

written onto a PROM, it remains there forever. Unlike RAM, PROM keeps their data stored

when the computer is turned off. The difference between a PROM and a ROM (read-only

memory) is that a PROM is manufactured as blank memory, whereas a ROM is programmed

during the manufacturing process.

Erasable Programmable read only memory (EPROM):

EPROM Differs from PROM or ROM in that it can be erased by exposing it to strong ultraviolet light.

Do you notice the difference in the graphics of RAM and those of ROM and PROM? There is an area to

program and erase the code for the PROM and EPROM.

Now that you have read this note, let’s see if this short video will help you some more. It is a bit

outdated with cassette and disk but the concept is the same!

Comparison chart

RAM ROM

Definition Random Access Memory or RAM is a form of data storage that can be accessed randomly at any time, in any order and from any physical location. allowing quick access and manipulation.

Read-only memory or ROM is also a form of data storage that cannot be easily altered or reprogrammed. Stores instructions that are not necessary for re-booting up to make the computer operate when it is switched off. They are hardwired.

Stands for

Random Access Memory Read-only memory

Use RAM allows the computer to read data quickly to run applications. It allows reading and writing.

ROM stores the program required to initially boot the computer. It only allows reading.

Volatility RAM is volatile i.e. its contents are lost when the device is powered off.

It is non-volatile i.e. its contents are retained even when the device is powered off.

Types The two main types of RAM are static RAM and dynamic RAM.

The types of ROM include PROM, EPROM and EEPROM.

Manipulate units of storage

Units of Storage

As we store more data and information on our secondary storage devices and media, it is

important that we know how large a file is and how much space we have left on our device.

Let's see if we can understand these concepts of data size, storage capacities, flash drive size, and

so on.

How to transform from one unit to the other:

One character (say for example the letter 'a') = 1 bit

8 bits = 1 byte

Remember bistable devices? On or off, 0 or 1? Well a bit can be in one of two states! On or off,

0 or 1.

we can therefore store 2 8 bytes or 1024 bytes = 1 Kilobyte (KB)

1024 kilobytes = 1 Megabyte (MB)

1024 Megabytes = 1 Gigabyte (GB)

1024 Gigabytes = 1 Terabyte (TB)

CONVERTING BETWEEN UNITS:

Example 1: If we have 1 Kilobyte and want to know how many bits it contains:

1 Kilobyte = 1024 Bytes

and 1 Byte = 8 bits

Therefore

1 Kilobyte = 1024 Bytes

= 1024 X 8 bits

= 8192 bits

Example 2: We want to know how many bytes there is in 2 Megabyte::

1 Megabyte = 1024 Kilobytes

1 Kilobyte = 1024 Bytes

SO!

1 Kilobyte = 1024 Bytes

AND

1024 Kilobytes = 1024 * 1024 Bytes = 1048576 Bytes

AND

1 Megabyte = 1024 Kilobytes

= 1,048,576 Bytes (1 KB) X 1024

= 1,073,741,824 Bytes

Therefore 2 Megabytes = 2 X 1073,741,824 Bytes

= 2,147,483,648 Bytes

Compare the types of secondary storage media

with respect to portability, speed and capacity

Secondary storage media

There are several types of secondary storage media, some are seldom used while others used

daily. Let us compare these media in terms of portability, speed and capacity. Here are

discussions on some Secondary Storage Devices:

Storage Media Portability Speed Capacity

Magnetic Tape

Composes a thin tape

with a coating of a fine

magnetic material Cheaper and are more

durable

The tape itself is thin or

narrow and is portable.

However, the tape needs

to be inserted in a tape

drive for the data to be

read

Slowest of all storage

media,

so ideal for backing

up old data

(archiving)

Can store up to about 5

Terabytes

Floppy Disk

Were popular in the 1980's and

early 2000's

The disk itself is small

enough to be portable.

However, the disk needs

to be inserted in a disk

drive for the data to be

read

Floppy disks sizes were

5.5-inches, and 8-inches,

but the popular size was

3.5-inches.

Very slow to access

and store data

Between 640kb and

1.44 Mb

Hard Disk

A Hard Disk is normally mounted

inside a case.

Usually there are multiple hard

disks stored in a hard disk drive.

Hard disks that are used

internally in a computer

system are not portable.

However, there are now

some external hard

drives

Very fast compared to

the floppy and

magnetic disk

Range from hundreds

of megabytes to

hundreds of gigabytes

or terabytes

Optical Disks

Flat, circular, plastic or glass disk on which data is stored in the form of light and dark pits.

Types:

Compact Disk (CD):

CD-ROM: CD-Read Only Memory - data cannot be erased from it

CD-RW: CD-Rewritable, these disks can be erased and rewritten at any time.

Portable Faster than magnetic

tape, but slower than

hard disk or flash

memory

CD: Can transfer

data up to the speed

of 7800 KB/s, or

about 70 minutes of

audio.

CD: About 650 MB

Digital Versatile Disk (DVD):

DVD-ROM:DVD-Read Only

Memory - data cannot be erased

from it

DVD-RW: DVD-Rewritable,

these disks can be erased and

rewritten at any time.

DVD: access rates of

600 KBps to 1.3

MBps

DVD: Ranges from

4.7 GB to 17 GB

Flash Drive

small external storage device,

typically the size of a

finger; inexpensive and durable

Portable 30 to 100′s of MB

(megabytes per

second)

8 Megabytes to 512 Gigabytes

Flash Memory Card

An EEPROM non-volatile

computer storage chip.

They are flat and also have a

smaller version which is used

within cell phones

Portable About 15 MB/s 1 Gigabytes -16

Gigabytes

Let's put access speed for some devices in order:

Use terms associated with storage devices

Read/Write Head

Disk read/write heads are the small parts of a disk drive that move above the disk platter. Once

the read/write head "crashes" onto a platter, data recovery is highly unlikely at best.

A Hard Disk is divided into concentric tracks.

Tracks are divided into sectors (pie slices)

A sector is the smallest addressable unit on the disk.

Data on this hard disk is positioned into these tracks and sectors so they can be easily read by the heads and

also to help reduce fragmentation on the hard disk

When a program read data from the disk, the operating system finds the surface, track and sector

containing that byte of data and reads that entire sector into a special area in main memory called

a buffer.

Data on a hard drive are accessed by two methods:

1. Fixed Head: Hard Disks with fixed heads have a read/write head for each track on the hard

disk, since there is no moving of heads to access data, the data access time is generally faster.

2. Moving Head: A moving head hard disk is one in which one or more read-write heads are

attached to a movable arm which allows each head to cover many tracks of information

Device Interfaces

Device Interfaces can be either Parallel or Serial.

A parallel interface transfers data simultaneously in multiple bits. Common parallel interfaces include SCSI

and ATA also known as IDE.

1. SCSI (small computer system interface)

SCSI is a parallel interface used for attaching peripheral devices such as printers to computers. These are used by Apple Macintosh computers, IBM computers and many UNIX systems. These SCSI interfaces provide data transmission rates up to 80 MB per second.

2. ATA / IDE

This interface is used to connect hard disk drives, CD ROM drives and similar peripherals to the controller on the motherboard. They can transfer up to between 8 and 100 MB per second.

A serial interface transmits data serially by using packets of bits where it is able to transfer the data faster than the parallel interface.

1. SATA (Serial ATA)

SATA uses a single cable with a minimum of four wires which creates a point to point connection between two devices

Transfer rates for SATA are minimum 150 MB per second.

Here is a comparison of a SATA hard drive and an IDE Hard drive showing the connectors:

8. STATE THE TYPES AND FUNCTIONS OF OUTPUT

DEVICES

Output Devices

You should take a quick review of the functions of the components of the computer and its peripherals. Two important peripherals are INPUT and OUTPUT devices.

We have already looked at Input devices (they accept data into a computer)

So let's turn our attention to Output devices (they output data or information from the computer).

Information can be output from a device in the form of sound, movement, printed pages, images and so on. This section addresses output of printed pages and images.

Visual Display Units

Visual Display Units (VDUs) are used to display text, images and numbers in a rage of colour.

Types of VDUs: The most common output device used with desktop computers is the Visual display unit (VDU) which first looked like an old television set (diagram at left above) but was replaced by flat-screen monitors such as Liquid Crystal Display (LCD) (above right).

Laptop computers have Thin Film Transistor (TFT) displays since they are smaller in size overall.

Many Televisions and Monitors are LCD, although plasma screens are the current trend with large screen sizes up to 60". Apart from being used in homes for watching downloaded videos, they are also used as hanging screens in reception areas to display information.

Resolution: The output you see on a monitor is made up of thousands of tiny coloured dots called pixels. The more pixels that the monitor can show the better quality of the output

Advantages

Relatively cheap and reliable Can display text and graphics in a wide range of colours. They do not waste paper.

Disadvantages

Output is not permanent Not suitable for users with visual problems.

Printers

Printers produce a printed 'hard copy' of your output on paper which is a permanent output that can be physically distributed held or used away from the computer. Apart from printing on paper, some printers can also print directly on to a CD or DVD.

A major factor with printers is the cost of the ink, the speed to print the output and the quality of the printed output.

Different printers are suited to different purposes and have a range of purchase and costs.

Impact Printers

Impact printers are similar in action to a typewriter.

Dot-Matrix Printers

Dot matrix printers remain in common use in businesses where multi-part forms are printed. This allows the output to be printed on two or more sheets of paper through the carbon paper at the same

time. This is useful when the customer signs a copy on a multi-part printed form, keeps one copy and another copy is kept for filing, and say, a third copy is sent to process the order.

Dot matrix printers use a print head containing a line of pins. As the print head passes over the

paper, the pins impact on the inked ribbon (shown below) forming characters on the paper.

Dot matrix ribbon

Advantages

Can print duplicate copies simultaneously when quality is not a priority Very cheap Very noisy when printing

Disadvantages

Cannot print high quality images Slow to print

Sample of printed document showing low quality of output

Non-Impact Printers

Inkjet printers are examples of non-impact printers. They operate by using droplets of ink onto the page.

Inkjet Printer

Ink-jets are better for low volume printing as they produce good quality output of text and graphics.

These printers use cartridges that contain the ink. Colour ink-jet printers are ideal for use at home where only a few documents need to be printed and the quality of the printout is not a priority

Ink-jet cartridge

Advantages

Inkjet printers are cheaper than lasers They can produce high quality images for photos Ideal for home use

Disadvantages

Slower than lasers Relatively expensive Colour printing can be slow and use up lots of ink Cartridges need to be replaced more often than with the laser printer The ink can be smudged if still wet on the paper The ink can saturate the paper

Laser Printer

Lasers are examples of non-impact printers. A laser printer rapidly produces high quality text and graphics.

Laser printers are similar to photocopiers as they use toner cartridges. They are used mainly because they are quiet, and can quickly print large quantities of high quality printed output such as text and graphics.

Laser printers can print in black and white for manuals and other documents or in colour for flyers and brochures.

More recently there are laser-jet printers which are a cheaper laser printer with features of both the laser and ink-jet printer.

Toner cartridge

Advantages

Fast printing Cheaper to produce large volumes of printing High quality printouts - better than ink-jet or dot-matrix

Quiet printing compared to ink-jet and dot-matrix

Disadvantages

It is probably the most expensive printer, especially the colour printer The toner it uses is more expensive than the ink cartridges of the ink-jet and ribbon for the

dot-matrix Takes up a larger space than the ink-jet or dot-matrix

Plotter

Plotters are a specialist type of printer which print high quality images on very large pieces of paper such as, say 4 feet wide by 8 feet long. They are used by engineers, architects and map-makers to draw plans of buildings, diagrams of machines or large scale maps.

Advantages

cheap to run can produce very precise technical drawings

Disadvantages

It is hard to combine colours as you would in an inkjet Slow

Machine-Readable and Human-Readable Output Devices

You should take a quick review of the functions of the components of the computer and its peripherals. Two

important peripherals are INPUT and OUTPUT devices.

We have already looked at Input devices (they accept data into a computer)

So let's turn our attention to Output devices (they output data or information from the computer).

Information can be output from a device in the form of sound, movement, printed pages, images

and so on. This section addresses output of that can be read by users only or by computers only

Machine-Readable Devices

Machine readable devices are those that output data or information in a form only a computer can process.

Machine readable documents are those where the written or printed characters and or words can be scanned

and interpreted by Optical Character Recognition (OCR) software, and converted into an electronic document.

Machine readable devices include:

Disks (Floppy, CD, DVD , flash disks, and so on)

Magnetic Tapes Sensors (light, pressure, heat, and so on)

The following are machine-readable, and require a machine-readable device:

Barcode QR Code

Human-Readable Devices

Output devices produce hard or soft copies of data or information that can be read and interpreted by

users (humans).

Any document that a human can read and understand without needing the reader's native language is human-

readable.

Human readable devices include:

Computer Screen or monitor Printer Keyboard Mouse

The following are human-readable and can be read or interpreted by users:

9. DESCRIBE HOW DATA ARE STORED AND MANIPULATED

WITHIN THE COMPUTER

Binary

Computer systems manipulate numbers. Inside the computer, the numbers are represented as bits

or bytes that represent words.

For example, the number three is represented by a byte with bits 0 and 1 set; 00000011. This is numbering

system using base 2. People commonly use a decimal or Base 10 numbering system. What this means is that in

Base 10, count from 0 to 9 before adding another digit. The number 22 in Base 10 means we have 2 sets of

10's and 2 sets of 1's.

Base 2 is also known as binary since there can only be two values for a specific digit; either a 0

= OFF or a 1 = ON. You cannot have a number represented as 22 in binary notation. The decimal

number 22 is represented in binary as 00010110 which by following the below chart breaks

down to:

Bit Position 7 6 5 4 3 2 1 0

1 1 1 1 1 1 1 1

Decimal 128 64 32 16 8 4 2 1

22 or 00010110:

All numbers representing 0 are not counted, 128, 64, 32, 8, 1 because 0 represents OFF

However, numbers representing 1 are counted, 16 + 4 + 2 = 22 because 1 represents ON

Decimal Values and Binary Equivalents chart

Decimal Binary

1 1

2 10

3 11

4 100

5 101

6 110

7 111

8 1000

9 1001

10 1010

16 10000

32 100000

64 1000000

100 1100100

256 100000000

512 1000000000

1000 1111101000

1024 10000000000

1. A base 2 number system that uses 8-bits has each represented by the numeric values of 0 or 1,

also known as ON or OFF, UP or DOWN, and is the primary language that computers use to

communicate.

Below is an example of the maximum 8-bit value of 255, which is 11111111 in binary.

To get this value add each column, so 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255.

Value: 128 64 32 16 8 4 2 1

ON/OFF: 1 1 1 1 1 1 1 1

Tip: Counting on a computer normally start with 0, instead of 1. Therefore, counting all the bits

does equal 255, however, if you start at 0, it is really 256.

Below is another example of 10001101, which is 141 or 1 + 4 + 8 + 128.

Value: 128 64 32 16 8 4 2 1

ON/OFF: 1 0 0 0 1 1 0 1

Real Numbers

There are two types of real numbers, Fixed-Point and Floating Point.

Fixed Point

Fixed point data items are numbers which have embedded decimal point i.e. 1.5,

458.4589, -0.569.

Floating Point

Floating point data items are numbers, which are, held as binary fractions by a computer.

The numbers are expressed in a form where you have a mantissa and an exponent. The exponent

indicates how many digits the decimal point should move. For example an exponent of 2

indicates that you move the decimal point to the right by two places to get the original number

12.3. Then, an exponent of -3 would take the decimal point to the left by three places to again,

obtain the 0.000123.

Note that we are not changing the original number, only representing it in a different form so that

it can be stored in the computer.

Number Mantissa Exponent

12.3 = 0.123 * 102 0.123 2

123000 = 0.123 * 106 0.123 6

0.000123 =0.123 * 10-3

0.123 -3

Signs and Magnitude in Binary

Negative signs are not used in binary however the bit zero (0) at the furthest left is used to

indicate that a number is positive. While a 1 placed at the furthest left of a note indicates that

the number is negative. For example:

001011012 is positive

101011012 is negative

If you are given a four bit number example such as 10012 and you are asked to represent it as an

8 bit negative binary number, you can add zeroes as a place filler to the left then a 1 at the on

the eighth until you have bits in total.

For example 10012 as an eighth bit negative number is 100010012. 10012 displayed as a positive

number 000010012.

000010012= 910

100010012 = -910

Binary Coded Decimal (BCD). This is a method used to represent decimal numbers in a simpler way. If you were to convert 25010 to binary you would normally have to divide it by 2 and record the remainders. However using Binary Coded Decimal (BCD), each digit is represented in binary by a 4-bit binary code.

Digit (Base 10) Binary code

0 0000

1 0001

2 0010

3 0011

4 0100

5 0101

6 0110

7 0111

8 1000

9 1001

Therefore 25010 can be represented as 2 5 0 0010 0101 0000 25010 = 0010010100002

We can take this a little further.

1010 = Positive sign (+)

1011 = Negative sign (-)

Therefore

250 represented in BCD is 1010 0010 0101 0000 + 2 5 0 And

-250 represented in BCD is 1011 0010 0101 0000 - 2 5 0

Octal

A base-8 number system commonly used to represent binary numbers and other numbers in a

shorter form. Below is a basic chart of how a binary number comprising 8 bits is converted to an

octal number.

Binary 1 1 1 1 1 1 1 1

Octal +200 +100 +40 +20 +10 +4 +2 +1

Below are some binary examples and their octal equivalents.

10001111 =

200 + 0 + 0 + 0 + 10 + 4 + 2 + 1 = 217

10101111 =

200 + 0 + 40 + 0 + 10 + 4 + 2 + 1 = 257

Can you calculate 11010100 to be 324?

Hexadecimal numbering system

The other major numbering system used by computers is hexadecimal, or Base 16. In this

system, the numbers are counted from 0 to 9, then letters A to F before adding another digit. The

letter A through F represents decimal numbers 10 through 15, respectively.

The chart below indicates the values of the hexadecimal position compared to 16 raised to a power and

decimal values. It is much easier to work with large numbers using hexadecimal values than decimal.

To convert a value from hexadecimal to binary, you merely translate each hexadecimal digit into

its 4-bit binary equivalent. Hexadecimal numbers have either and 0x prefix or an h suffix. For

example, the hexadecimal number:

0x3F7A

Translates into, Using the Binary chart and the below chart for Hex:

0011 1111 0111 1010

Decimal Hexadecimal Binary

0 0 0000

1 1 0001

2 2 0010

3 3 0011

4 4 0100

5 5 0101

6 6 0110

7 7 0111

8 8 1000

9 9 1001

10 A 1010

11 B 1011

12 C 1100

13 D 1101

14 E 1110

15 F 1111

1. Alternatively referred to as Base 16 and hex, the hexadecimal numbering system uses

combinations of 16 digits and characters (letters) to represent all numerical values. In addition to

the ten numbers in the decimal system (0, 1, 2, 3, 4, 5, 6, 7, 8 and 9), hexadecimal also uses the

letters A through F to create a hexadecimal number.

For example, "computer hope" in hexadecimal becomes "636f6d707574657220686f7065".

Anyone who has designed a web page has encountered hexadecimal value when doing colors.

For example, to create red text use the HTML color code #FF0000, which translates to 255 Red,

0 Green, and 0 Blue in hexadecimal.

Ones complement

To convert a number using the ones complement, simply change the 0s to 1s and the 1s to 0s.

So the ones complement of 111010112 is 000101002. Also the ones complement of 000101002 is

111010112.

Two’s complement

This is another method for representing signed integers.

Steps

a. Write the integer in its sign and magnitude form

b. Flip the bits, i.e. change all 1’s to 0’s to 1’s

c. Add a bit 1 to this number

Example

Write the following decimal integers two’s complement representation using 8 – bit store:

a) 9

b) -9

Solution

a) 0000 0110 sign and magnitude form

1111 0110 flip the bits

Ans 1111 0111 add bit 1

b) 1000 1001 sign and magnitude

0111 0110 flip the bits

Ans 0111 0111 add bit 1

ASCII codes (American Standard Code for Information Interchange)

So far we have been using binary to represent numbers. ASCII codes is used to represent number, symbols as well as things as DELETE, BACKSPACE, etc. Basic concept of the ASCII Each code takes up 1 byte (8bits) Capital letters are represented with the binary digits for: 65 – 90 Lower case letters by the binary digits for: 97 – 122

The digits 0 – 9 by the binary digits for: 49 – 57 Example The ASCII code for D is 010001002. What is the binary code for W? D is the 4th letter of the alphabet while W is the 23rd. 23 – 4 = 19. We should therefore add the binary equivalent 19 to the ASCII code of D. Thus: binary code for D 01000100 Binary code for 19 +00010011 01010111 The ASCII code for W is 010101112

10. INTERPRET THE HARDWARE SPECIFICATIONS OF A COMPUTER

SYSTEM

This page is mostly taken from https://wikis.engrade.com/interpretthehardwarespec

The hardware specifications of a computer will vary depending on what you mainly want to use it

for. If you want to use a computer for work that involves Microsoft Office applications, using email

and surfing the Internet, then those specifications will be quite different from using a computer for

interactive games that use lots of graphics and video.

Take a look at this advertisement that was copied from an online store.

Intel® Core™ i5-4430 processor + 6M Cache, up to 3.2 GHz. This high-performance CPU Running

on an Asus P5GC-MX 945GC motherboard, a 1TB - 7200RPM SATA II hard drive, 6GB DDR3-

1333MHz SDRAM, XFX GeForce 7300 GT 512MB DDR2 PCI Express Video Card, 10/100/1000

Ethernet card, 802.11b/g/n WLAN and a Blu-ray player & SuperMulti DVD burner, Microsoft

Windows 8

To many of us, this may be similar to understanding Latin, Let’s try to analyze some of this.

Intel® Core™ i5-4430 processor + 6M Cache, up to 3.2 GHz -

The two major players in the processor arena are Intel and AMD. Intel makes the "Core Duo" and "i”

series" class of processors.

AMD makes the "Athlon" and "Opteron" class of processors.

The Pentium and Athlon processors are Intel and AMD's low end and cheaper processors and would

be the ones to choose if you wanted a computer for email, surfing the Internet and using Microsoft

Office applications such as Word.

The higher end Opteron or Intel Core processor is best for gaming programs with lots of graphics or

business oriented software tasks.

There is no need to make a choice between AMD or Intel at this point, other than comparing price.

The CPU or processor

The two name features of CPUs that you need to be aware of are its speed and type.

The processor speeds of most of today's PCs are measured in GHz (Gigahertz). 1 GHZ means that it

can execute approximately 1 billion instructions per section.

The CPU type determines the type of application for which a particular type of processor is used.

The two most popular companies that currently produce CPUs are Intel and AMD. Intel processors

are little more expensive than AMD's due to the small difference in performance.

Main Memory

The capacity of a computer's memory determines the number of programs that it can hold at a time,

which affects the performance of a computer system. More memory indicates that it can hold more

programs at a time. Modern PCs memory capacity is measured in GB (Gigabytes).

There are two main types of RAM - SDRAM (Synchronous Dynamic RAM) and RDRAM (Ramous Dynamic

RAM). RDRAM is faster and more expensive than SDRAM and is used mainly for high performance

computers.

Word size determines the number of bits that can be stored and processed at a time by the CPU. Most

modern PCs have a word size of either 32-bit off 64-bit.

RAM speed determines how fast the chip updates the data that it contains. In modern PCs it is

measured in MHz (Megahertz) and is usually above 400MHz.

Hard drive

Storage capacity determines how much information can be stored for later use. More hard disk

space means you can store more programs and data. In modern PCs it is measured in Gigabytes

(GB) but are reaching up to Terabytes (TB).

Hard disk speed is normally expressed in revolutions per minute (rpm). The rpm is how fast the disk

is spinning and varies from 5400 rpm - 15000 rpm.

Other specifications

Ports

A computer system need to send and receive information from peripheral devices. A port is a piece

of technology that is used to connect external devices to a computer.

Parallel: used mainly to connect printers but can also be used to connect certain scanners and

external hard disks.

Serial: Used to connect certain types of mouse, modem and printers.

Universal Serial Bus (USB) Used to connect around 127 devices including printers, scanners, flash

drives and digital cameras. There are USB-1 and USB-2 (this one is faster).

Firewire/IEEE 1394: used to transfer video images from digital devices.

Expansion Slots

Expansion slots are sockets found on the motherboard and are used to insert additional circuit

boards (cards). They can be used for adding more memory, graphics facilities and other special

devices. There are three types of expansion slots:

1) Peripheral Component Interconnect (PCI) - used to attach sound cards, network cards and video

cards.

2) Accelerated Graphics Port (AGP) - mainly used for graphics cards

3)Industry Standard Architecture (ISA) - used for attaching modems and not commonly seen on

most modern computers.

DISTINGUISH BETWEEN SYSTEMS PROGRAMS AND

APPLICATION PROGRAMS

Application Programs

Application programs are groups of programs that help the computer to carry out a specific task, such as

creating a brochure.

To make most output devices run we need to use the correct type of software. Application

software is software designed to help the user to perform specific tasks. Here is an example to help

differentiate between application software and system software:

Computer Games are for entertainment for the user, so it is categorized as application

software

Virus scanning program scans to prevent damage to programs and help the computer to

run better, therefore it is system software

Application software is designed for users to perform tasks and create documents using different

applications. These tasks can include creating a word document, playing a computer game,

analyze data using a spreadsheet, database. There are several categories of application software

such as:

General purpose application software. Special purpose application software. Custom written application software

General purpose application software

General purpose application software can be used for a variety of tasks. These types of software

are not usually limited to one particular function. For example a word processor could be classed

as general purpose software as it would allow a user to write a report, perform mail merge, and

create a brochure or an exam paper.

Examples of General Purpose application software include generic Word processors,

Spreadsheet, Database and Presentation software.

Examples:

Word processing - for writing letters, reports and other documents.

Examples: Microsoft Word, Word Perfect.

Facilities include: editing of text, font & size changing, find & replace, spell checker, word

count, mail merging (combining data from a database with text in a standard letter to produce

customised letters).

Desk-top Publishing (DTP) - for producing posters, leaflets and newspapers.

Examples: Microsoft Publisher, Adobe PageMaker.

Facilities include: ability to import text and images from other programs or from disk plus ability

to position them individually on the page. Usually have some text editing tools included.

Data handling - for creating databases.

Examples: Microsoft Access.

Facilities include: creation & editing of fields, sorting and searching records and displaying data

in graphical or chart form.

Spreadsheet modeling - for producing invoices and cost plans. Can be used to create models,

simulations or expert systems for others to use.

Examples: Microsoft Excel, Lotus 1-2-3.

Facilities include: entry of formulas to perform calculations, also ability to display data in

graphical and chart form. Acts rather like a multifunction pocket calculator, but once set up for a

particular purpose there is no need to remember all the formula and functions each time you use

it.

Graphics package - for drawing and painting.

Examples: Photoshop.

Facilities include: cropping, resizing, various digital filters, drawing, painting and editing tools.

Computer-Aided Design (CAD) - for floor layouts and product design.

Examples: 2D Design, AutoCAD.

Facilities include: various drawing and editing tools and ability to scale accurately, sometimes in

three dimensions and with ability to rotate in any direction.

Presentation software - for demonstrations and lectures to live audiences.

Examples: Microsoft PowerPoint, Prezi.

Facilities provided to produce and edit on screen multimedia presentations involving text,

images, video and sound.

Music software - for composing a musical performance.

Example: Sibelius.

Facilities provided to create, edit, store, print and play scripts; to record, process and replay a

variety of sounds via input from a music keyboard and other "midi" instruments.

Special purpose application software

Special purpose application software created for one specific task. For example a camera

application on your mobile phone deals specifically with taking and sharing photos. Other

examples would be a Solitaire game (it would only allow you to play solitaire), calculators, media

players, and calendar programs since they perform SPECIFIC tasks.

Custom written application software

Custom written application software, also called 'Bespoke application software' is software that

is made for a specific user and purpose, so this type of software is not widespread. For example a

factory may require software to program a robot to lift huge crates of eggs, so the software

required would have to be specially built for the task since not many businesses will lift huge

crates of eggs.

Other examples might include software for the military, the space shuttle program, software for

3-D scans in hospitals and other medical equipment, software being written for specific tasks in

financial institutions.

Application Programs

Application programs are groups of programs that help the computer to carry out a specific task, such as

creating a brochure.

To make most output devices run we need to use the correct type of software. Application

software is software designed to help the user to perform specific tasks. Here is an example to help

differentiate between application software and system software:

Computer Games are for entertainment for the user, so it is categorized as application

software

Virus scanning program scans to prevent damage to programs and help the computer to

run better, therefore it is system software

Application software is designed for users to perform tasks and create documents using different

applications. These tasks can include creating a word document, playing a computer game,

analyze data using a spreadsheet, database. There are several categories of application software

such as:

General purpose application software. Special purpose application software. Custom written application software

General purpose application software

General purpose application software can be used for a variety of tasks. These types of software

are not usually limited to one particular function. For example a word processor could be classed

as general purpose software as it would allow a user to write a report, perform mail merge, create

a brochure or an exam paper.

Examples of General Purpose application software include generic Word processors,

Spreadsheet, Database and Presentation software.

Examples:

Word processing - for writing letters, reports and other documents.

Examples: Microsoft Word, Word Perfect.

Facilities include: editing of text, font & size changing, find & replace, spell checker, word

count, mail merging (combining data from a database with text in a standard letter to produce

customised letters).

Desk-top Publishing (DTP) - for producing posters, leaflets and newspapers.

Examples: Microsoft Publisher, Adobe PageMaker.

Facilities include: ability to import text and images from other programs or from disk plus ability

to position them individually on the page. Usually have some text editing tools included.

Data handling - for creating databases.

Examples: Microsoft Access.

Facilities include: creation & editing of fields, sorting and searching records and displaying data

in graphical or chart form.

Spreadsheet modeling - for producing invoices and cost plans. Can be used to create models,

simulations or expert systems for others to use.

Examples: Microsoft Excel, Lotus 1-2-3.

Facilities include: entry of formulas to perform calculations, also ability to display data in

graphical and chart form. Acts rather like a multifunction pocket calculator, but once set up for a

particular purpose there is no need to remember all the formula and functions each time you use

it.

Graphics package - for drawing and painting.

Examples: Photoshop.

Facilities include: cropping, resizing, various digital filters, drawing, painting and editing tools.

Computer-Aided Design (CAD) - for floor layouts and product design.

Examples: 2D Design, AutoCAD.

Facilities include: various drawing and editing tools and ability to scale accurately, sometimes in

three dimensions and with ability to rotate in any direction.

Presentation software - for demonstrations and lectures to live audiences.

Examples: Microsoft PowerPoint, Prezi.

Facilities provided to produce and edit on screen multimedia presentations involving text,

images, video and sound.

Music software - for composing a musical performance.

Example: Sibelius.

Facilities provided to create, edit, store, print and play scripts; to record, process and replay a

variety of sounds via input from a music keyboard and other "midi" instruments.

Special purpose application software

Special purpose application software created for one specific task. For example a camera

application on your mobile phone deals specifically with taking and sharing photos. Other

examples would be a Solitaire game (it would only allow you to play solitaire), calculators, media

players, and calendar programs since they perform SPECIFIC tasks.

Custom written application software

Custom written application software, also called 'Bespoke application software' is software that

is made for a specific user and purpose, so this type of software is not widespread. For example a

factory may require software to program a robot to lift huge crates of eggs, so the software

required would have to be specially built for the task since not many businesses will lift huge

crates of eggs.

Other examples might include software for the military, the space shuttle program, software for

3-D scans in hospitals and other medical equipment, software being written for specific tasks in

financial institutions.

System Programs / Systems Software

System programs are software that manages computer peripheral devices. The term Systems Software is used for the programs that handle the running of your computer's hardware.

Modern computers are complex instruments involving many different parts. System software is necessary to control and manage the running of various computer components along with ensuring that the computer performs at its best.

The three main categories of system software are:

Operating Systems Translators Utilities

Operating Systems

An operating system is systems software, consisting of programs and data that manage computer hardware resources (like printers, monitors etc), and provides services to keep the applications running or performing as they should. An operating system therefore acts as an intermediary or a 'go between' between a user of a computer and the computer software and hardware.

These are a collection of programs that manage most of the work in helping you get your tasks completed. Examples of Operating Systems include Windows XP, Widows 8 or Linux). These are the programs that interpret commands issued by application software (such as your word processor or spreadsheet). Operating systems can be found on almost any device that contains a computer, from mobile phones and video game consoles to supercomputers and web servers.

The Operating System is also acts as an interface between the application software and the computer meaning that without the operating system, the application programs would be unable to communicate with the computer.

Utility programs These are small, powerful programs that the user accesses to maintain a smooth running of the

computer Examples of Utility programs include file management (copy, paste, delete, file searching), disk defragmenter, disk cleanup.

Many other utility programs can also be installed and used for various purposes

Examples of utility software include:

Virus scanner: protects your system from viruses Disk defragmenter: speeds up your hard disk System monitor: looks at your current system resources File managers: adds, deletes, renames and moves files and folders

Translator software (Compiler, Assembler, Interpreter)

Translator software allows new programs to be written and run on computers, by converting source code into machine code. Three types are:

Interpreter - converts third generation languages (such as JavaScript) into machine code one line at a time

Compiler - converts 3rd generation languages (such as Pascal, C++) into machine code all at once

Assembler - converts assembly code into machine code Software can be described as computer programs that provide instructions for telling computer

hardware how to process data and interact with devices.

Hardware and Software need to work well together since hardware has limited performance

without software and software would not be able to run at all without the support of

hardware.

12. EXPLAIN THE FUNCTIONS OF AN OPERATING SYSTEM

Functions of an Operating System

Before we look closely at the functions of an operating system, let's review the purpose of an operating system.

It is systems software, consisting of programs and data that manage computer hardware resources (like

printers, monitors etc), and provides services to keep the applications running or performing as they should.

An operating system therefore acts as an intermediary or a 'go between' between a user of a computer and the

computer hardware.

An operating system has the following functions:

File Management Memory Management Input/Output Management Secondary Storage Management Process Management

File Management Since files are collections of documents or programs created by users, they need to be kept and stored so that

they can be easily found. Files are usually given names so (1) that they can be located and (2) users know what

types of files they are using such as word documents, excel files or a Paint Program. Format of a file Files are named so that the user knows where the file is located and what type of file it is, such as, the hard

drive letter, folder or directory name, file name and file extension: Examples of file names include: C:/PROJECTS/Functions.doc Excel_SBA.xls Word_SBA.docx When managing files, the user also needs to know some information about the file such as

the file’s type (e.g. excel file, word, file, graphics file), the file’s size, in bytes who created the file, information about other potential users of this file, access constraints on the current user and other users, dates and times of creation, last access and last modification, dates and times of last backup and recovery

So, the operating system's responsibilities regarding file management include:

File creation and deletion. Directory or folder creation and deletion. Control over the creation, movement and deletion of files and folders. File backup on secondary storage media.

Memory Management

Memory management handles or manages primary memory to keep track of every memory location that is

either allocated to some process or is free. It checks how much memory is to be allocated to a process and

decides which process will get memory and at what time. It also tracks whenever memory becomes free or unallocated.

A process can be swapped temporarily out of main memory to secondary storage and then brought back into

memory for continued execution.

Typical secondary storage used is a hard disk drive or any other secondary storage which is fast in access and

large enough to accommodate copies of all memory images. It must be capable of providing direct access to

these memory images.

Major time consuming part of swapping is the transfer time in swapping the process between main memory

and secondary storage.

Here is a video which explains a bit on memory management:

Security Management

If a computer program is used by an unauthorized user then he/she may cause severe damage to computer or

data stored in it. Operating System security involves specified steps or procedures used to protect the

Operating System from these unwanted access, viruses, worms, malware or remote hacker intrusions.

Therefore many techniques are used to safeguard data from being stolen, edited or deleted if the operating

system security is compromised. One method is to set passwords at many levels, from prompting you for a

password when you system starts up, to using firewalls to keep viruses and hackers from accessing your work.

Authentication is a security management method that identifies each user of the system and associates the

executing programs with those users. It is the responsibility of the Operating System to create a protection

system which ensures that a user who is running a particular program is authentic. Operating Systems

generally identifies/authenticates users using following three ways:

Username / Password - enter a valid username and password to login into the system. User card/key - use a swipe card to login into the system. Biometrics - fingerprint/ eye retina pattern/ signature - User needs to scan body part over a special

input device used by operating system to login into the system.

Input/output Management A device driver is a program or routine developed for an input or output (I/O) device. The operating system

must ensure that the devices are used correctly by the executing programs. For example:

A printer must be managed so that the printed material from two different programs belong to the

correct documents and are not mixed together. A disk drive must be managed so that all programs get scheduled use of the disk for reads and writes.

User Interface User interfaces are discussed in more detail in section 15. Two types of user interfaces are: Command line user interface Graphical user interface Process Management

A process is a program in execution in a sequential manner.

As a process executes, it changes state, and therefore its current activity must be noted at all times. A process

can be in any one of the following states at any one time:

New: the process is being created

Ready: The process is waiting to be assigned to the processor so that it can be executed

Running: Process instructions are being executed

Waiting: The process is waiting for some event to occur before it can continue (such as the completion of some

other operation)

Terminated: The process has finished running.

13. Distinguish among multitasking, multiprocessing and

multiprogramming

Multiprogramming - A computer running more than one program at a time (like running Excel

and Firefox simultaneously). So two or more tasks or programs or processes can reside into the main

memory at one point of time.

Examples include using the computer to listen to a song on YouTube while playing a computer game and

working on an assignment using Microsoft Word, Excel and other applications simultaneously

Multiprocessing - A computer using more than one CPU at a time

Multitasking - Two or more tasks sharing a common resource (such as one CPU) at one point in time.

This is achieved by scheduling the instructions for the various tasks. So for example, a task may

be the one running at any given time, while another task waits to get a turn. These instructions are

managed so that the resource (e.g. CPU) switches from one task to another one

14. Explain the different types of processing modes

Types of Processing Modes

Before we describe these processing modes, let us first understand that groups of data or

transactions need to be processed to get information so that we can understand what the data

means or what information we get from those transactions. Therefore, there are different ways to

process this data or set of transactions. You can process them as they come, wait and process

them later or a combination or variation of these methods.

Batch Processing

Batch processing is used for very large files or where a fast response time is not critical.

A batch is also called a group, a set or a bunch. So, Batch Processing, as the term implies, processes data,

invoices or transactions, in a group or batch.

Batch processing is an efficient way of processing high volumes of data which can be carried out at any time,

but usually at the end-of-cycle processing, so the files or data to be transmitted or processed are gathered over

a period of time and then transmitted or processed together as a batch.

Examples of batch processing include processing a bank's reports at the end of a day, or generating monthly or

bi-weekly wages, or processing utility bills each month-end.

Here is a video to help you understand the concept of batch processing and how it involves more time to

complete a process

On-line Processing

On-line processing ensures that when a transaction is ready to be processed, it will be

immediately or almost immediately without delay.

An example to illustrate on-line processing would be having a printer plugged in and turned on

so that you can print your document at anytime without having to ask if the printer is plugged in

and turned on!

So ideally, data is processed by the system as it is entered.

Real-Time Processing

In order for real-time processing to occur the system must be on-line!

Processing is said to be real-time if the data or a transaction appears to take place, or actually takes place

immediately after entering the data or instruction to process the transaction. Therefore response time and

processing speed are very important.

So, real time data or transaction processing involves on input, the continuous processing and

output of data. The data or transaction must be processed in a short time period (or near real

time).

Examples include radar systems and bank Automatic Banking Machines (ATMs or ABMs).

Time-sharing

Sometimes many people are accessing and processing transactions from a system at the same

time. In order to complete each user's transaction, the computer system processes each user's

transaction in pieces, thus paying attention all user's transactions and completing them all.

Time Sharing therefore involves the sharing of computing resources among many users by

means of multiprogramming or multi-tasking.

15. Distinguish between types of user interface

An interface is a way to get instructions from the user to the computer and feedback from the

computer to the user.

There are three main ways in which users can input data or instructions to and get results or

feedback from the computer

Software Interface

Command Driven Interface

This type of interface means that all commands for the computer must be typed in using a

keyboard.

The prompt C:\Documents and Settings\Glenda> at the bottom of the screen is used

to enter commands.

This means that the commands must be known in order to get the correct results. Usually

programmers and experts would use the command driven interface.

Examples of Command driven interfaces are MS-DOS and UNIX.

Command Driven Interface

Menu Driven Interfaces

The Menu Driven Interface was an improvement over the Command Driven Interface. The user

now had menu options to choose from instead of having to memorize the commands.

Menu Driven Interface

Some popular programs now include a menu and ribbon so that the options are easily accessed,

as shown below:

Menu Driven Interface with Ribbon

Options from the menus can be pulled-down from the top of the screen as shown below...

...while other options pop-up anywhere on the screen, as shown below.

Graphical User Interface (GUI)

An improvement of the pop-up or pull-down menu driven interface is the Graphical User

Interface (GUI - pronounced GOO-ee).

In addition to the menu driven interface, this interface also uses pictures called icons to represent commands

and programs. So a picture of a printer would represent the option to print something. This makes it easier and

more user friendly for the user. The diagram below illustrates some of the icons of a GUI.

Examples of GUIs are Windows and MAC OS.

The mouse is typically used with a GUI.

Hardware Interface

Hardware interfaces are sometimes used to help with the input of data. Voice activated

interfaces, touch screens and Braille keyboards are some examples of hardware interfaces:

Some Automatic Banking Machines (ABMs)

have audio-controlled

instructions for the visually impaired.

Other ABMs have lights that blink to show the

user where the collect

cash or deposit envelopes.

Touch screens are becoming popular. They are

replacing

the use of the mouse as an input device where

the user's finger

acts as to select icons on the screen.

Braille Keyboards are also useful for the

visually impaired to input data to the computer.

End of Chapter Summary