Hardware: components that make up the computer system, for
example keyboard, mouse…
Software: programs that control the computer system. There are
two types of software
• Systems Software: programs that allow the hardware to run
properly
• Applications Software: program that allow user to do specific
tasks
A typical computer system is made up of hardware and software. It
also consists of:
• Input Devices: keyboard, mouse
• Output Devices: monitor, printer
• Secondary Storage Devices: DVD R/W drive, removable hard drive
• Another part of the computer system are the ‘Processor and
Internal Memory Devices’ called the central processing unit
(CPU), internal hard disk, random access memory (RAM) and
read only memory (ROM).
Central Processing Unit (CPU):
• Interprets and executes commands from the computer hardware
and software
• Made up of discrete components and numerous small integrated
circuits combined together on one or more circuit boards
• Due to manufacturing techniques, the term microprocessor is
used instead of CPU
• Found in many household devices where some monitoring is
needed
Internal Hard Drive:
• Computer’s main memory
• Where the applications software, disk operating system and data
files are stored
• Advantage of these memories is fast data transfer/access times
and the large capacity to store data
Random Access Memory (RAM):
• Internal chip where data is temporarily stored when running
applications
• Memory can be written to and read from
• Contents are lost when computer is turned off so it is often
referred to as a ‘temporary’ memory
Read Only Memory (ROM):
• Used to store permanent information
• Used to contain, for example, configuration fata for a computer system
• Chips cannot be altered and can only be read from
• Information stored on ROM chip is not lost when computer is turned off
• Referred to as ‘non-volatile’ memories
BIOS (basic input/output system):
• Coding contained in ROM known as boot file
• Stores fate, time and system configuration in a non-volatile chip called a CMOS
(complementary metal oxide semiconductor).
Operating System Tasks:
• Controlling the operation of the input, output and backing storage devices
• Supervising the loading, running and storage of applications programs
• Dealing with errors that occur in applications programs
• Maintaining security of the whole computer system
• Maintaining a computer log (which contains details of computer usage)
• Allowing communication between user and the computer system (user
interface)
Being able to communicate with the operating system is called the ‘user
interface’. Two main types of user interfaces: command line interfaces (CLIs) and
graphical user interfaces (GUIs).
Command Line Interfaces (CLIs):
• require users to type in instructions to do specific tasks
• user has to learn the commands to carry out basic operations
• the user is in direct communication with the computer
Graphical User Interfaces (GUIs)
• allow the user to interact with the computer using images and
symbols (icon) rather than having to type CLI codes
• use various technologies and devices to provide the user interface
like the windows icons menu and pointing device (WIMP)
developed for personal computers (PCs)
• uses a mouse to control a cursor, which selects icons to open/run
windows that can open many windows at the same time
• touch screen devices use post-WIMP interaction where fingers
are in contact with the screen
PC/Desktop Computers: General purpose computer, IBM compatible
Advantages
• Spare parts and connections tend to be standardized, which usually results in
low costs
• Desktops tend to have a better specification for a given price
• The large casing allows good dissipation of any heat build-up
Disadvantages
• Desktops are not particularly portable since they are made up of separate
components
• All the components need to be hooked up by wiring, which can be quite
complex and clutters up the desk space
• Because they are not particularly portable, it is necessary to copy files
Laptop Computers:
Extremely portable systems with these expected features:
• Low weight
• Low power consumption
• A processor that does not generate too much heat
Advantages
• Very portable, since the monitor, pointing device, keyboard, processor and backing
store units are all together in one single box
• There are no trailing wires
• Can take full advantage of WIFI
• Since they’re portable, the can link into any multimedia system
Disadvantages
• Since they’re portable, they are easy to steal
• Have limited battery life so the user may need to carry a heavy adaptor
• Keyboards and pointing devices can sometimes be awkward to use
• Heat dissipation is more difficult due to the structure of the laptop components
Netbooks: A computer that can almost fit onto a hand
Advantages
Netbooks have many features of laptops so it has similar advantages and
disadvantages
Disadvantages
In addition the disadvantages listed above:
• They don’t have optical drives
• Keyboards are only 80% the size of laptop keyboards
• Lack some of the features found in larger machines
Personal Digital Assistants (PDAs): Small handheld computers that comes
with a touch screen and a stylus
Advantages
• They can be used anywhere because of their size
• They are very lightweight and are more portable than laptop computers
Disadvantages
• It is difficult to enter text quickly
• Have very limited capabilities die to the software and the operating system
used
Mainframe Computer: Large, very powerful, computer system used to run commercial
applications where huge amounts of data need to be processed each day
Main Features
• They can have several CPUs
• They have very fast processor speeds
• They can support multiple operating systems
• They have huge amounts of storage capacity
• They have huge internal memories
• They often operate using time sharing or batch processing
Advantages
• Capable of doing very large jobs that require large memories and fast processor time
• Allow users to be given a time slice of the very powerful facilities
• Capable of very large number crunching and deal with complex mathematical functions
Disadvantages
• Need to be permanently housed in a large room
• Very expensive to operate and maintain