Chapter 1.1 Components of a Computer System and Modes of Use
1.1 (a and b) Hardware and Software Definitions
A computer system consists of hardware and software.
· An input device is any piece of hardware that allows data to be transmitted to the computer processor. No computer, however powerful, is of value unless it is possible to give it instructions and also data to be used when those instructions are carried out.
· An output device is any piece of hardware that allows the computer processor to convey information, or the results of its processing. There is no point in having a computer system carrying out processing of any sort unless the results of that processing can be either reported, or used to effect future input to the system.
· Storage is any piece of hardware which can store data outside the processor in a form which is suitable for input back into the processor. This is necessary because data must be saved for future use if the processor is switched off and for transfer from one machine to another.
The software of a computer system is the various sets of instructions which tell the system how to do things. These sets of instructions are collected together in workable groups known as programs. Without programs of instructions computers would not be able to function because they would not know what to do.
1.1. (c) Different Software Types
Sets of instructions to make a computer do something are grouped together as programs. These programs make up the software of a computer system.
Depending on the sort of task that a program is expected to accomplish they are grouped into different types of software.
· Operating system software is a set of programs, known as system programs, which control the operation of the computer system. They are responsible for the way that the pieces of hardware communicate with each other and for monitoring the way that the hardware of the system is used.
· User interface software is used to provide a method of communication between the person using the system and the system itself. Put very simply it is what you see on the screen when you are using the computer.
· Translator software is necessary because the computer uses a language that is difficult for human beings to understand and a computer is not capable of understanding human language. The translator software provides the computer with the equivalent of a Chinese-English dictionary so that it can look up what things mean.
· Utilities, or utility programs, are system programs designed to carry out common tasks, for instance the programs that control output to the printer or the storage of data.
· Programming languages are used to write sets of instructions that the processor can understand because it has a translator for that language. There are many different programming languages, each of which has been designed to solve a particular type of problem by having commands that are useful for solving the problem.
· Common applications software includes word processors, graphics, spreadsheets, and many others. These are the programs that you use to produce something worthwhile on the computer. They will be looked at in more detail in chapter 1.8.
Systems Software and Applications Packages
Systems Software
Computers are machines that can carry out operations very quickly. This does not mean that they are in any way intelligent. However fast the machine can work, it is useless if it does not know what to do. Computers need specific instructions for even the most trivial of tasks. If a computer user had to supply these instructions there would be very few people able to use one. Consequently, the manufacturer of the machine will provide programs that are accessible to the user by using very simple commands, these programs are the system software.
· The operating system is the set of programs that control how the computer responds to user requests. Examples that you may have used include DOS and Windows.
· Utility programs are additional routines that can be added to an operating system or that are available to the user within an operating system. An example that you may have on your computer system would be a piece of back-up software that can be used to make sure that you do not lose all your work when the computer fails.
· Some frequently used routines are stored in such a way that they are accessible to users. These routines are stored together in a system library, and form part of the system software. This is something of a grey area between system software and application software because application software also gives access to library areas.
· Program translators are needed in order to allow users to produce programs in a simple format which can then be translated into something which the computer will understand.
Applications Packages.
A piece of applications software is a program, or set of instructions, designed to make the computer carry out some task. It differs from system software in that it makes the computer do something that is useful for the user. Word word-processing software, or Paintbrush graphics software are both examples of applications software because they both allow the user to produce something that is of general use.
If the software can be used in many different situations to accomplish different things then it is said to be generic software. For example a word processor can be used to write a letter, or to produce a report, or type an essay,… A word processor is a piece of generic software.
If the software contains programs that allow lots of different tasks to be carried out, together with a book of instructions telling the user how the software should be used, then it is called an Applications Package.
An integrated package consists of several parts, each of which is an application package. Further, the integrated package is designed so that users can easily move data between the different parts of the integrated package. For example, if two of the parts are a word-processor and a drawing package, users can move a drawing, created using the drawing package, into the word processing package.
1.1. (d) Communications Hardware
Computing becomes really powerful when it is possible for different computers to communicate with each other. In order to do this the two computers that are ‘talking’ to each other will need to have a set of rules to keep to otherwise they will not understand each other, there is more about these rules in chapter 1.6. But there is no point in having rules if they are not connected together in some way. The hardware that is used to connect them is known as communications hardware.
Communications hardware can be as simple as a wire going from one computer to another, along which electronic signals can be sent. There are two problems with ‘hardwiring’, the first is that the computers are fixed according to where the wire is and the second is that there is a limit to how far the signal will travel down a wire before degrading and becoming useless.
The first problem can be solved by using radio communication or infra red or any means that does not need a wire.
The second problem can be solved by using a better quality wire to increase the range or by using the telephone lines that are already there. The problem with a telephone line is that it cannot take computer signals, so a special box is needed to change the computer signal to one that can go down the phone line, this box is a piece of communication hardware called a modem.
Whatever the means used to send the signals, the computer has to be able to get the signals ready for sending in the first place, it does this by using a special piece of communications hardware called a network card. The job of the network card is to connect the processor to the wire (or whatever is being used) so that information can be sent and received.
Example Questions.
1. Explain the difference between hardware and software. (2)
2. Give two reasons why a computer system would need to have some type of external storage device. (2)
3. Describe the difference between system software and application software. (2)
4. An integrated applications package contains a number of different pieces of generic software.
State what is meant by an integrated applications package and generic software. (3)
one part. In this type of question, some of the marks are always reserved for the last part of the question.
5. The computers used by two examiners, who live in different cities, need to communicate with each other. State two pieces of hardware that would be necessary to allow the computers to communicate and explain why each is necessary. (4)
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