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GCSE ICT Theory: SOFTWARE
What is software?
A computer system is made up of hardware and software. The hardware is the physical components like input, output and backing store devices. Software is the computer programs that instruct the computer to perform particular operations.
Software consists of very simple instructions that tell the computer what to do with the data that it is processing. These instructions are carried out so quickly the computer seems to be doing complicated things.
Systems Software - Operating System
Operating System Tasks:
Memory Management
Allocate memory to programs and make sure that one program does not interfere with memory allocated to another.
Communication
Handle communication between the different parts of the system so that they work together.
Data Transfer
Moving data between the different parts of the system - e.g. transfer of data from hard drive to memory. Handling input and output operations.
Processor management
Deciding which program should be given processor time and for how long.
Security
Detecting, handling and reporting error situations to minimise loss of data. Handling log-in for password protected systems.
Systems software is provided to ensure that the hardware works as computer and it usually supplied with the computer. The most important type of systems software is a special program called the operating system. This program is loaded and run when the computer is first started up. It performs a number of essential tasks and it remains loaded in memory all the time that the computer is switched on. It is responsible for controlling and managing the way that the different components of the computer system communicate and interact. The user's programs (applications software) will call on the operating system to carry out many basic tasks.
For example if a word processor program needed to print a page of text it would pass the output to the operating system. The operating system would communicate with the printer to make sure that it was available and ready to print. It would then pass the output to the printer.
Since an operating system is a computer program, it is possible to run different operating systems on the same computer, the user can select the operating system that is most appropriate at the time. This is an important consideration because a particular application that the user has bought may require a particular operating system.
The operating system will determine the way that the computer behaves. Two important types of operating system are multi-tasking and multi-user.
Multi-tasking operating systems allow several programs to be loaded and apparently running at the same time. For example one program might be accepting input from the keyboard while another is reading data from a disk, processing and printing it.
In order to achieve this the operating system will allow each of the different programs access to the central processing unit (CPU) in turn. The CPU will actually process one program's data at a time. When that program cannot continue immediately - perhaps because it is waiting for data to be found on a hard drive - then the operating system will hand the processor over to another program that can continue. In this way the CPU, which is the fastest part of the computer, is kept busy and does not have to wait for data transfers to or from slow peripherals because it can get on processing data for another program.
A multi-tasking operating system will need to ensure that two programs do not try to access the same peripheral at the same time preventing, for example, printout from two programs being mixed up. It will also need to manage memory so that one program does not interfere with the memory allocated to another. In large computer systems it will also select the next program to load in when it detects that there are resources available to run it.
Multi-user operating systems allow more than one person to use the computer at a time. The computer will be connected to a number of terminals. The operating system will allocate a short amount of time to each terminal. During this time it will check the terminal to see if it needs processor time. If it does then that terminal's job will be processed for a short length of time. At the end of that time the operating system will move on to the next terminal so that each is checked and given processor time in turn. This is the system used in supermarkets to allow the shop's computer to handle several checkout terminals at once.
A multi-user operating system will need to identify each user who logs on to a terminal and ensure that they have access to their data. It will also need to ensure that users cannot gain unauthorised access to other users' data and software.
Systems Software - Utilities
Utilities programs allow the user to carry out various computer-related tasks. For example the user may need to format a floppy disk or to find the location of a file on the hard drive. Different utility programs will allow the user to carry out these tasks.
Although utility programs are part of the systems software, they are not usually part of the operating system. The operating system is always loaded while the computer is running. A utility program will usually be loaded and run only when the particular task it performs needs to be carried out.
Applications Software
Systems software is important because it makes the computer hardware work as a computer system. However the computer user will have bought the computer system to perform one or more tasks. The software that makes the computer perform these user-related tasks is called applications software.
Some applications software may be written to perform a particular specialised task, such as stock control or payroll for particular company. Other applications such as a word processor program or spreadsheet may be general purpose or generic. Generic software can be used in a variety of ways for different purposes. A word processor program could be used to produce posters, prepare legal documents or write a school assignment.
Nearly all applications programs can be customised. This allows the user to set up the application in a way that suits them. Examples of customisation include setting up special dictionaries for a word processor, choosing the format for currency or dates and setting default fonts and background colours.
Non-generic (task specific) Applications Software:
Payroll
Game
Stock-control
Customer Billing
Generic (general purpose) Applications Software:
Word processor
Desk-top-publisher
Database
Spreadsheet
Software needs to be customisable because it will usually be used by a large number of users each having different needs. If the software can be customised then the user can configure it to in a way that allows them to work efficiently. For this reason generic packages such as word processors, spreadsheets and databases usually include a large number of configuration options. A non-generic application, written for one specific purpose, will normally have fewer configuration options because there will be a more limited user base and the tasks that the users will carry out are more clearly defined.
Sometimes a customer's software needs cannot be met by an existing package. In this case software may be specially written for the customer. This is called bespoke software and the customer should end up with an application that exactly matches his or her needs. However software development costs are high so this is an expensive option. In addition it can take a months or even years for software to be developed. Once the software has been produced it is likely to have a number of bugs that will need to be sorted out.
