Chapter One

1.1 Hardware and software:

Computer systems are now commonplace in every part of our daily life. This chapter introduces the basic components that make up these computer systems. Comparing books with computers is a good analogy: the actual pages and the ink used on the pages are equivalent to the hardware used to make up these computers; the words written on these pages are equivalent to the software. Without the words, the book is useless. Similarly, without software, computers would be of little use to any of us.

• Hardware is a general term for the physical components that make up a computer system, for example keyboard, mouse, monitor, processor, circuit board and so on.

• Software is a general term for the programs that control the computer system.

There are two types of software:

Systems software: programs that allow the hardware to run properly, e.g. operating systems

Applications software: programs that allow the user to do specific tasks, e.g. spreadsheets.

1.2 Main components of computer systems

A typical computer system is made up of hardware and software. The image below shows an example of a computer system consisting of input devices, output devices and secondary storage include:

Input devices: keyboard, mouse

Output devices: monitor, printer

Secondary storage devices: DVD R/W drive, removable hard drive.

However, one part of the computer system has not yet been mentioned. This is shown as the ‘Processor and internal memory devices’ in the diagram – this consists of four key components called the central processing unit (CPU), internal hard disk, random access memory (RAM) and read only memory (ROM).

• A processor (CPU) is the logic circuitry that responds to and processes the basic instructions that drive a computer.
• An internal hard drive is the primary storage device located inside a computer system. It usually contains pre-installed software applications, the operating system and other files.
• RAM (Random Access Memory) is the hardware in a computing device where the operating system (OS), application programs and data in current use are kept so they can be quickly reached by the device’s processor. RAM is the main memory in a computer.
• ROM (read-only memory) is a non-volatile memory type. This means it receives data and permanently writes it on a chip, and it lasts even after you turn off your computer. The data is coded to not be overwritten, so it’s used for things like your printer software or your startup programs.

The central processing unit (CPU): is the part of the computer which interprets and executes the commands from the computer hardware and software. CPUs used to be made up of discrete components and numerous small integrated circuits, which were combined together on one or more circuit board/s.

1.3 Operating systems

An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.

To enable users to communicate with computer systems, special software, known as operating systems, have been developed. The general tasks for a typical operating system include:

• 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).

Computer users need to be able to communicate with the operating system – this is called the ‘user interface’. There are two main types of user interfaces: command line interfaces (CLIs) and graphical user interfaces (GUIs).

Command line interfaces

CLIs require a user to type in instructions in order  to choose options from menus, open software etc. There are often a number of commands that need to be typed in, for example, to save or load a file.

You can code CLI using CMD.

1.4 Types of computers

There are many types of computer systems in existence. This section summarizes some of the more common types currently available.

• PC/desktop computers:

PC/desktop usually refers to a general purpose computer which is made up of separate monitor, keyboard, mouse and processor unit.

Advantages:

• Spare parts and connections tend to be standardized, which usually results in low costs.
• Desktops tend to have a better specification (e.g. faster processor) for a given price (often due to size and construction constraints in laptops).
• 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, etc. when you want to do some work elsewhere (e.g. at home).

• Laptop computers

Laptop (or notebook) refers to a type of computer where the monitor, keyboard, pointing device and processor are all together in one single unit. This makes them extremely portable systems.

The key features you would expect to find in a laptop are:

• low weight (to aid portability)
• low power consumption (and also long battery life)
• a processor that does not generate too much heat (cooling is very important).

Advantages:

• They are 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, etc. because everything is in one single unit.
• Since they are portable, they can link into any multimedia system.

Disadvantages:

• Since they are portable, they are easy to steal!
• They have limited battery life so the user may need to carry a heavy adaptor.
• The keyboards and pointing devices can sometimes be awkward to use.
• Heat dissipation is more difficult due to the structure of the laptop computers.

• Netbooks:

Netbook is a term used to describe a computer that can almost fit onto a hand and is a smaller version of a laptop. These used to be known as palmtop computers, but this term now generally applies to much smaller devices which use touch screens and often a stylus to key in data (see below).

 Advantages:

Netbook computers have many of the features of laptops and therefore have similar advantages and disadvantages.

Disadvantages:

In addition to the disadvantages listed above for laptops:

• Netbooks don’t have optical drives
• The keyboards are only about 80 per cent the size of laptop keyboards

• Personal digital assistants:

Personal digital assistants (PDAs) are small handheld computers that usually come with a touch screen that is activated using a stylus. Data (e.g. text) is entered by using a keyboard that appears on the touch screen. Originally, these devices were used as personal organizers but their use has expanded somewhat to include new generation mobile phones, data loggers, satellite navigation systems, etc. Many PDAs now have basic database, word-processing and spreadsheet facilities.

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.
• They have very limited capabilities due to the software and the operating system used.