Components of a Computer System and Modes
of Use
Hardware, software, input devices, storage
devices and output devices
Hardware
Hardware is the physical - mostly electrical - components which
make up the computer system. Examples of hardware would be the
motherboard and a device controller circuit board.
Software
Software are the programs - made up of program instructions -
which run on the hardware. Software makes the hardware useable.
Input devices
One of the fundamentals principles of any computer system is
that its operation consists of a continuous cycle of input -
processing - output.
Consider when a user key in a search phrase to say
Amazon (the input) - the computer system searches the database for
that product (the processing) and then produce the search result
(the output).
Consider the embedded computer system inside a
washing machine. A user selects the wash programme to use on their
washing machine (the input) - the computer system senses that the
door is shut etc. (the processing) and an LED display shows the
wash time remaining (the output).
The keyboard
The standard QWERTY keyboard is the widely used input
device.
Sensors
Sensors are used to 'sense' physical attributes in the
real-world. Specialist input devices These are often designed for
the rapid input of large quantities of data such as optical
character recognition (for billing applications) and high speed
scanning devices.
Storage
Temporary storage
Short term storage is required for the intermediate processing
of data. The Amazon search example requires that the search results
are temporarily stored immediately before being displayed to the
user. This type of storage is called primary storage.
Permanent storage
Permanent storage is required for all files which are used by
the computer system. A personal computer (PC) which has the
programs and user's data stored on the PC will all require
permanent storage. This is done with an internal hard drive. This
type of storage is called secondary storage.
Output devices
A monitor used as a display screen is the most popular output
device. Other forms of output would be hard copy using a printer or
some form of sound using speakers/earphones such as speech output
or simply a warning 'bleep' to the user.
Central Processing Unit
Primary storage
↑
↓
Input → Processor → Output
↑
↓
Secondary storage
Different types of
software
Software falls into two categories:
• system software
• applications software
Operating System
The one piece of software which will be provided when we
purchase a computer is the operating system. The computer system is
unusable without an operating system.
The role of operating system is to manage the
resources of the processor.
The operating system provides the interface between
the hardware and the user and hides all the complexities of the
hardware away from the user.
Operating system
↗
System software → Programming language translators
↘ Utility programs
↘ Library programs
↗
Classification of software
General purpose applications software
↘
↗
Applications Software → Special purpose applications software
↘ Bespoke software
Applications programs
Applications programs are generally mass marketed and so the
user will have a choice to make.
Applications programs can be classified as either:
• general purpose applications programs
• special purpose applications programs
General purpose applications
Also known as 'generic' software. A general purpose applications
program can be used for a variety of tasks.
Word processor
A word processor can be used for a variety of task
including:
• basic word processing
• producing a company report
• writing a textbook etc.
The software has features for the basic creation, saving,
retrieval and editing of text.
Spread sheet
A spreadsheet consists of a grid of columns and rows called
cells into which text, numbers and formulae can be arranged.
A spreadsheet can be used for a variety of tasks:
• presenting a costing for an event such as a music concert
> This allows for 'what-if' type use - what if we increase
the cost of a ticket to $30? What effect will this have on the
projected profit?
• maintaining a simple list of information.
Database
Early databases were little more that a computerised 'card
file'. Modern relational databases and database management systems
are the backbone of most large commercial applications.
Presentation software
There are now many different applications of presentation
software, such as Microsoft Power Point, that it can be classified
as general purpose. Applications include:
• a student presentation of some research work
• teaching a new topic to a class
• running a rolling display of slides advertising the school at
a marketing event.
As the presentation is in electronic form it can be distributed
on a magnetic medium or through a website to make it more widely
available.
General points
Many of these general purpose software programs (for example,
Microsoft Office) now come with a built-in programming language
(for example, Visual Basic for Applications) and so this extends
the scope of the software's usage and so fits even closer to our
definition of being 'suitable for a variety of tasks').
Use of general purpose software is the 'starting
point' to develop a computer solution which assumes that:
• an audit of the features available with (for example a
spreadsheet) has been done and we are satisfied that the required
software features are present from which the solution can be
produced
• the user has sufficient skills with the software to do
this.
Special purpose applications software
Special purpose software is software designed for one particular
task. The list of applications and uses is almost endless!
Route planner software
The software is designed for the user to key in the start and
final destination (could be the name of the town or some form of
postal code). The software calculates and displays the route,
estimated time etc.
Tax calculator software
The only task for which this is appropriate is the calculation
of the income tax a person will have to pay.
Bespoke software
Bespoke software is written for a particular client following
their program specification. For example, the software needed for a
Examiner to upload all the marks from the scripts they have been
allocated was written specifically for Examinations.