Components of an Information System

Difference Between Hardware and Software

Hardware:• Physical equipment that makes up a computer system• If you can kick it or take an axe to it it is hardware.

Software:• Programs, routines and procedures (together with their

associated documentation) which can be run on a computer system.

It is important not to confuse the media used to transport software with software itself

• A CD is a piece of hardware which you can touch and kick and it may contain software which you cannot touch.

• The CD is not software it is hardware

Examples of Hardware Hardware:

• Central Processor

• Peripherals – these are hardware devices which are attached to the central processor:

» They can be classified into four types: Input:

– Keyboard, Mouse, Scanner Output:

– Monitor, Speakers Backing Storage:

– Hard Disk, Floppy Disk Drive Communications:

– Modem

Standardisation In general, hardware produced by one company

will not be compatible with that produced by another

Hardware:• A POS terminal by IBM could not plug into an ICL system

Software:• A program written for the Mac would not run on a PC

Standardisation Software standardisation

• Output may appear different:» E.g. web pages viewed on different systems

Different layout, resolution of images, etc.

• Standardisation of file formats» Importing and exporting of data between applications

Advantages of Standardisation• Hardware and software will be known to be compatible• Choices from where to purchase equipment• Agreed standards for equipment – comeback if not up to standard

Disadvantages of standardisation• Less choice• Less competition amongst suppliers

Components of a Computer Control Unit

• This is the part of the central processor (CPU) which manages the execution of instructions. The control unit fetches each instruction in sequence, decodes and synchronises it before executing it by sending control signals to other parts of the computer.

Arithmetic and Logic Unit (ALU)• This is the part of the CPU where data is processed and

manipulated. This consists of arithmetic and logic operations.

Random Access Memory (RAM)• Memory which holds data loaded from the backing store – data

that the computer is to process, screen display etc.

Computer Performance Machine Cycle

• A computer runs on a clock – a 2.5 GHz machine is running at 2.5 thousand million cycles per second. Each cycle is a clock pulse. The faster the clock, the more instructions per second.

• The complexity of the instructions affects the speed of processing. » A program consisting of a larger number of simple instructions drawn from

a reduced instruction set (RISC) may run faster than an equivalent program consisting of a smaller number of complex instructions drawn from an extended instruction set (CISC).

Number of Processors• A single processor can only run 1 instruction at a time. To get beyond

this you need an additional processor. This allows more than one instruction to be run and increases the speed of the computer. Programs and computers have to be written to make use of the second processor.

Computer Performance (cont.) Bus Speed

• The speed of the computer is also determined by how fast the data can travel. Data travels down buses

• Increasing the speed of the bus decreases the waiting time and increases the speed. The speed of the bus is determined by the clock speed

RAM• The more RAM you have, the more instructions you can store without having

to access the disk which is slow. It decreases disk thrashing

• Cache memory is even faster and with more of it, the machine runs faster still

Dedicated Processing Devices• Instead of using the processor to do all the processing you can use specialist

processors to take some of the load and thus speed up the machine. These include sound and graphics processors

Making a Machine Run Faster Hardware Options

• Replace motherboard» Increases BUS speed

• Processor» Add second/subsequent processor

» Overclocking processor

• Dedicated device» Dedicated processing device – sound card/graphics card, etc

• RAM» Increase RAM – holds larger swap files/more data

Making a Machine Run Faster Software Options

• Defragment Hard Drive» Increases BUS speed

• Remove Unused Programs» Frees up hard drive space» Large swap file

• Memory Optimiser» Better use of memory

• Replace programs with up to date ones» Make better use of memory and resources

• Patch software / run anti virus / anti spyware» Remove programs using resources

Input Devices

Keyboard Numeric Keypad

Joystick Mouse

Trackerball Microphone

Touch Screen Scanners

OCR Digital Camera

Graphics Tablet Digitiser

Push Switch Sensor

ADC Foot Mouse

Puff Suck Switch Eye-Typer

Examples include:

Output Devices

Loud Speaker

Printer

Monitor

Plotter

Buzzer

LED

Examples include:

Loud Speaker Used to give confirmation of actions

Can be used to read lines of text

Increased use with CDs and Music (MP3s)

Music technology requires specialist sound output devices.

LED and Buzzer

LED• Can display the status of a device

» FDD light displayed when in use

» Lights on a Printer indicates status - on-line or off line for example.

• Can be used to signal to hearing impaired people

Buzzers• Gives confirmatory actions

» Set sounds to events in Windows

» Bar Codes beep to indicate successful entry

Printers

Three main types of printers:• Impact Printers

• InkJet Printers

• Laser Printers

Choice of:• Colour

• Black and White

Selection of different resolutions

Impact Printers Physical Connection between print head and

paper Noisy Slow (chain printers can be very fast) Cheap to run Colour or Black and White Low Resolution Can do Carbon Copies Print on multi part paper

InkJet Printers Ink is fired at the page and the number of DPI can

be very high• High resolution

Colour or black and white High running costs Faster than a dot matrix but not as fast as laser Can not print carbon copies

Laser Printers High Quality Images Fast Printing Colour or Black and White (Colour is expensive) Medium to low running costs Excellent Quality Need special transparencies to produce OHPs Cannot do Carbon Copies

Monitor (VDU) Most common Output device Range of Sizes – standard is 17”, but 21” or

greater is available for specialists: • For example, designers• Newspapers and magazines

High quality output Bulky, but LCD screens can reduce footprint size

• More expensive than standard monitors• Less affected by glare• Fewer health issues compared to standard monitors

Possible health issues with standard VDU’s

Storage Devices

Tape

Hard Disk

Floppy Disk

CD ROM / R / RW

Other Storage Devices

Examples include:

Role of Storage Devices To store data that is not currently being processed

Non volatile storage of programs and data

Sometimes referred to as secondary store or mass storage.

Tape Serial Access to data

Used almost exclusively to hold backup data

Can hold in excess of 100Gb of data

Specialist devices required to read the tape

Slow access to data.

Hard Disk Sealed unit holding many GB of data Fast direct access to the data. Two types (standards):

• SCSI (Small Computer Systems Interface)» High speed of transfer (historically – catching up)

» Specialist card required – controller separate from device

» Can daisy chain devices

» MTBF (mean time between failures) greater on SCSI – reliability

• IDE (Integrated Device Electronics)» Standard interface in PC’s (More common than SCSI)

» Cheaper and slower than SCSI (catching up in speed)

Floppy Disk Floppy Disk Drive is standard on PCs Portable between machines Limited storage capacity (1.44 MB) Slow access to data Can be set to read only by use of a tag Inexpensive Constant use increases unreliability

CD ROM WORM (Write Once Read Many)

• Holds 650 MB Data

• Used for static data (data which does not change)» Encyclopaedias

» Software Programs

RW CDs allow you to rewrite onto the CD. • This is only possible a limited number of times and requires specialist

equipment. (approximately 1000)

DVD now available – Holds 12GB of data• Also RW DVDs

CDs/DVDs used to hold Music, Video, Pictures, etc.

Other Devices Zip disks (100 MB, 250 MB, 750MB etc) Super Floppy Disk (120 MB) Jazz Disks (1GB +) Flash Memory (1 GB+)

All storage devices are pushing amount of storage they can hold• Figures constantly changing

Magnetic v Optical Devices Magnetic

• Disk or Tape» Can be reused many times

» Very large storage capacity

Optical• CD Rom, DVD

» RW CD ROMs/RW DVDs exist – limited life cycle

» Limited storage capacity

Backup and Archive Backup

• Making copies of data or programs in case the originals are lost or corrupted.

Archive• The storage of information for long periods of time.

• Removing the data from the original medium and transferring it to off line/secondary storage

Considerations of Media: Speed of Backup (Direct or Serial) and speed of recovery Amount of data (MB or GB) Portability (Tapes, Removable disk) Compatibility with other systems (CD, tape, etc)

Hardware Related to Use Answers based on:

• Portability

• Specialist hardware required

• Cost

• Speed

• Ease of use

• Compatibility

Types of Software Operating Systems User Interfaces Utilities Translation Application Programming Languages

Operating Systems A program or suite of programs that control the

entire operation of the computer. Deals with the basic functions of the computer. At a technical level, it handles the basic and

central functions such as input and output operations and interrupts.

Examples include: MS-DOS, OS/2, UNIX, RISC-OS, Windows XP, LINUX, BeOS, etc.

User Interfaces Methods by which the user can interface with the

operating system/application• Command line

• Dialog boxes

• Menus

• Windows

Utilities Designed to perform a commonplace task, for

example the transfer of data from one storage device to another, sorting a set of data, disk editor.

They are designed to make the operation of the computer easier.

Other examples: formatting programs, backup programs, anti-virus, etc.

Translation Programs which convert a program from one

language to another, for example from low level language to machine code.

This is the general name for three types of translators:• Assemblers

• Compilers

• Interpreters

Application Generic Tailor-Made Off-the-shelf Programming Languages

Cross over between categories:• Generic is off-the-shelf• Programming languages can be off-the-shelf and used to create

tailor-made software

Generic These are off-the-shelf packages which do not

meet a specific purpose but serve a general purpose

For example:• Microsoft Office and components• Corel Suite• Lotus Suite

» Word Processors, Spreadsheets, Databases

The software can then be customised to produce the result you want.

Tailor-Made Either:

• Bespoke» The application is written for the purpose by a software house

Disads: Time consuming, expensive, limited support/books. Ads: Fulfils purpose, individual support

Or:• Customisation

» A generic application is customised using a programming language Disads: Need to purchase the application and you get more than

required. Ads: Cheaper, lots of support.

Off-the-Shelf Purchasing solutions from a shop without

alteration For example:

• SAGE payroll package• Heritage Library Database

The idea is to be able to open the package and run the software which delivers a specific solution

Can be generic (word processors)

Programming Languages There are a variety of programming languages

available. Each language has a specific purpose

• FORTRAN – Formula Translation» Mathematical and Scientific

• COBOL – Common Business Orientated Language» Business, Data Processing

Languages can also be used to enhance the application:• Use of VBA to write macros, or write dll’s