Software

Systems Software Computers require two types of software Applications software ; such as word processing, spreadsheet or graphics packages Operating systems software : to control and monitor the running of application programs, and allow users to communicate with the computer

Functions of an operating system Memory management. Resource allocation and scheduling Backing store management Interrupt handling Allowing a user to communicate with the computer

Utility programs As well as the basic operating system, the systems software available to users includes numerous utility programs, such as: Virus checkers - check disks and memory for viruses and delete them if detected; Security and accounting software - checks user IDs and passwords, counts and reports the number of attempts made to log on under each user ID, the amount of processor time used at each session, total login time and so on;

Utility programs (continued) File management utilities - attempt to repair corrupted files, reorganise files on disk so that free space is ‘defragmented’, ‘zip’ (compress) files so that they occupy less space.

DOS (Disk Operating System) tells the computer how to format, read and write information on disk (either floppy or hard) manages peripheral devices such as printer and keyboard controls the execution of application software Also specifies how many files can be held in a disk directory what is an acceptable file or directory name the number of bytes that can be on a disk the amount of memory usable by a program

Command-driven interface eg DOS The user had to type in commands in exactly the correct syntax to perform any operation This allowed complex commands to be entered to customise the operating system for a particular user Experienced users could perform operations faster using DOS than by using a mouse and menus or icons in a Windows interface 1.   Each digit of the code number is assigned a ‘weight’. The right hand (least significant) digit is given a weight of 2, the next digit to the left 3 and so on. 2.   Each digit is multiplied by its weight and the products added together. 3.   The sum of the products is divided by 11 and the remainder obtained. 4.   The remainder is subtracted from 11 to give the check digit. The two exceptions are: If remainder is 0, check digit is 0, not 11 If remainder is 1, check digit is X, not 10 Example: To calculate the check digit for the number 1587: Original code number 1 5 8 7 Weights 5 4 3 2 Multiply digit by its weight 5 20 24 14 Add products together 5 + 20 + 24 + 14 = 63 Divide by 11 5 remainder 8 Sub remainder from 11 11 - 8 = 3 Check digit = 3. Complete code number is 15873. To check that a code number is valid, it is not necessary to recalculate the check digit completely. If the check digit itself is assigned a weight of 1, and the products of the digits (including the check digit) and their respective weights are calculated, their sum will be divisible by 11 if the check digit is correct.

Operating Systems DOS Windows Apple Macintosh (MacOS) UNIX Linux

Systems software Operating system Utility programs perform common useful tasks such as search for lost files, sort files of data into a particular sequence, copy disk files to magnetic tape for backup purposes and so on. Programming language compilers / interpreters are different types of program used to translate the statements in a programming language such as Pascal, Visual Basic or C into a form that the computer can understand.

Systems software (continued) Performance monitoring software is used to monitor, analyse and report on the performance of a computer and its components. It can provide information such as the overall utilisation of the processor and number of disk accesses over a given period of time. Communications software In a mainframe environment, this is executed on a separate, dedicated processor (‘front-end processor’) and controls the flow of data to and from remote locations.

Applications software Written to perform specific tasks such as order entry, payroll, stock control or hospital appointments May be designed specifically for a company (‘bespoke software’) and written especially for them using a programming language or software such as a database management system Alternatively, the software may be purchased ‘off the shelf’

General purpose software Includes all common application packages such as: word processing desktop publishing spreadsheet database computer-aided design (CAD) presentation graphics. Most general purpose software is sold as a package, including a CD containing the software and manuals to help you get started and to be used as a reference.

Productivity tools used by organisations include Integrated packages WP, SS, DBs Presentation Graphics (Powerpoint) Communications Integrated packages combine features from all five of these once very popular because they offered capabilities from all these packages in a single product at a relatively low price, and data could be transferred between applications. However, have fewer and less sophisticated features than are found in separately purchased packages.

Productivity tools (continued) Software suites offer four or more products packaged together cheaper than buying the packages separately e.g. Microsoft Office includes Word, Excel, Access, a multimedia presentation graphics package called PowerPoint and Microsoft Mail. Lotus SmartSuite