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Computer Software
Computer software refers to a set of instructions that direct a computer on what to do. Computer software is classified into two main categories:
- System software
- Application software 1) System software Manages the operation of the computer itself, and makes sure that the computer works efficiently. It enables the user to communicate with the computer and its hardware e.g. mouse. Examples of system software: i). Operating system: It’s a set of programs that control and supervise the hardware resources of a computer during processing. Examples are: Microsoft Windows 95/98/2000/XP/Vista/NT, Macintosh OS, OS/2, CP/M, VMS, UNIX, MS-DOS ii). Firmware: also referred to as stored logic , It’s a combination of both hardware and software etched on a single silicon chip which accepts and interprets external commands from the user. iii). Utility software: also called service programs , is software that provides support to the application software. It performs commonly used services that make certain aspects of computing to go on more smoothly. Can also be defined as special programs used to enhance performance of the system. Functions of the utility software
- Formatting disk s
- Repairing diskettes
- Renaming files
- Sorting files
- Copying and deleting files
- Repairing damaged files, etc. Examples of utility software: System level, application utility, program translator, settings editor, text editor, sort editor, graphics editor, file manager, calculator, time, backup utility, recovery utility, compress/decompress utility, defragment utility, antivirus utility, diagnostic utility, sound player utility, internet browsing utility, calendar utility. iv). Networking software: It’s used to establish communication between two or more computers by linking them using a communication channel e.g cables to create network. Also it enables computers and other peripheral devices connected on a network to communicate and share resources. Examples: Novel Netware and Linux 2) Application Software Are designed to help the end - user to accomplish their tasks. Application software can be either a general purpose/off the shelf software or Custom /Tailor made software.
a). General purpose /off the shelf software – are not written to solve any particular problem, and can be used in different ways depending on the problem to be solved These programs are developed by software engineers, packaged and made available for purchase through a vendor. Off-the – shelf software are widely used because; It takes less time to assess company’s needs, buy and install them They are less expensive to acquire and maintain They are readily available for almost any task They are thoroughly tested before being released hence less chances of errors Easily modified to meet specific user needs. Disadvantages May not meet special needs They are not as efficient as made programs When changes occur extra costs is usually needed from user Not all packages are compatible with all computer system They may have some features not needed by user which may take extra storage Examples of general purpose software :
- Word processor – for typing documents like letters e.g. Ms Word, Lotus, Word Pro, WordStar
- Database – for keeping records e.g. Ms Access, Dbase, FoxPro, Paradox
- Spreadsheets – for calculations e.g. Ms Excel, Lotus 1- 2 - 3, Quattro Pro.
- Desktop Publishing (DTP) – designing publication like cards, pamphlets, magazines e.g. Adobe PageMaker, Ms Publisher
- Computer Aided Design – for technical drawing e.g. AutoCAD
- Graphics software – for designing and manipulating graphics e.g. Corel Draw, Adobe Photoshop. b). Special purpose/Custom/ tailor made software These programs are designed/tailored to meet specific needs of an organization. e.g in banks for managing their operations, airlines for booking, school for grading and test analysis etc. The software may be developed In- house or developed by a Software house to meet the specific requirements of an organization. It is expensive and needs specific Training to be able to use it. Classification according to End – User Licence (EUL) Software may be classified as open source(non-proprietary), proprietary or freeware. Open source software – is a software whose source code (programmed set of instruction) is freely made available to users. Users are encouraged to modify and distribute the modified product. Proprietary software – are software whose source code is hidden from users. Modifications can only be made by the software manufacturer. They are licensed to users at a fee or applied freely. Examples are; Microsoft Operating Systems, Microsoft Office, Adobe PageMaker and CorelDraw suit. Freeware are software products that are freely made available to the user. Some may be malicious software.
Reliability Good software must be reliable and secure.
3.0 OPERATING SYSTEM
3.1 Definition:
An operating system (OS) is the program that manages all the other programs in a computer. An operating system is a set of programs that manage computer hardware resources and provide common services for application software. Is a group of programs that manage all activities on the computer. Main program that controls the execution of user applications and enables the user to access the hardware and software resources of a computer. A program that controls the execution of an application programs and acts as an interface between the user of a computer and the computer hardware. The operating system provides a software platform on top of which other programs (application programs), can run. Examples of Operating Systems: Microsoft Windows XP/Vista 8/10/NT, Macintosh OS, OS/2, CP/M, VMS, UNIX, MS-DOS
3. 2 Functions of Operating System
i). Processor/ job Scheduling(CPU) Processor scheduling refers to allocating each job waiting for execution processor time at each given interval. The processor can only handle one task at a time. A job is a group of tasks taken as a unit of work for a computer which may include one or more computer programs, files and instructions to the Operating System. The [OS] scheduler decides which of the jobs is allocated to the CPU for processing first. ii). Resource control and allocation Includes controlling the use of computer resources by other system software and application programs being executed. The resources include I/O devices, CPU and processing time. The OS strives to avoid deadlocks by allocating resources wisely to tasks or programs that are competing for them. Each device has unique identification number called an interrupt number. So when two tasks request to use a resource at the same time, the one with higher4 priority interrupt is granted control. Deadlock is a situation where a particular task holds a needed resource and refuses to release it for use by other tasks. Analogy: John has a pen but needs a book to write on while Mary has a book but needs a pen to write with. Neither of the two wants to release whatever they have for the other to use first. Hence a deadlock occurs because neither is able to write.
iii). Input / Output management The OS coordinates between I/O devices and other peripheral devices making sure that data flows properly between them and sorting out any possible confusion. It will also monitor the state of I/o devices and signal any faults detected. It also governs the input/Output of data and their location, storage and retrieval. iv). Memory management Since data and instruction entered into the computer are temporary held in the main memory before and after processing. Since RAM is a scarce resource, the OS determines which task remains in memory awaiting for execution and which one will be kicked out back to secondary storage. The OS organize the main memory into partitions called page frames. Processes are equally divided into pieces that can fit into the frames called pages. The OS swaps pages between the main memory and the secondary storage. and ensures that each program and the data it requires are allocated adequate space in memory To access data or instruction, the OS knows where to find each piece of data as long as the correct address of the partition is used. In the hard disk where pages are held is referred to as Virtual memory. v). Communication control and management The OS manages various communication devices and provide protocols that governs communication between devices on a network. vi). Error handling The operating system alerts the user of errors that may arise out of illegal operations, hardware or software failure. The OS deals with errors produced during program execution by expressing what the error is and provides the error correction routines to ensure smooth operations within the CPU. vii). Security Modern operating systems implement security policies such that unauthorized users cannot get access to a computer or network resource. viii). Job sequencing The OS keeps a list of tasks currently being run and arranges them in a particular order to make it easy for the processor to execute them and to know how and when to fetch instructions and data for each task. i.e. clocks them in and out of the processor. v). Interrupt handling An interrupt is a break from the normal sequential processing of instructions in a program. The OS determines the cause of the interrupt and transfer the control to the most appropriate program. An external request causes the processor to stop executing the current task, and do something else before returning the control back to the program that was interrupted. Each hardware device communicates to the processor using Interrupt Request Number (IRQ number) which is a special number.
Enables the user to choose commands, start programs and see lists of files and other options by pointing and clicking at objects icons or pictures that appear on the screen. Besides menus, GUI make use of rectangular frames called windows , graphical objects called icons, most commands are executed using a pointing device. These features are given an acronym WIMP which stands for windows, icons, menus and pointer. Examples GUI operating systems include Microsoft Windows 95/98/2000/XP/Vista, MacOS and Linux.
3.4 Factors to consider when choosing an operating system
Hardware configuration of the computer such as the memory capacity, processor speed and hard disk capacity The type of computer in terms of size and make. Basic design of the computer is it IBM Compatible or Apple Computer. Applications intended for the computer User friendliness of the operating system, GUI will be preferred. Cost of the operating system The documentation available Availability in the market e.g. Microsoft Windows based OSs are very common. Reliability and security provided by the OS– can it run without crashing or hanging. Hanging is to stop responding to commands. The number of users it can support Review Questions 3.
- Give examples of two multi-user operating systems.
- Describe four functions of operating system.
- What is an interrupt?
- Name and explain four types of human computer interfaces.
- What are the advantages of GUI based operating system over the command-line?
- Differentiate between Multitasking and Multi-user operating system.
- Outline the factors you would consider if you were to buy an operating system.
- What is deadlock in reference to the operating system?
- Outline the factors you would consider if you were to buy an operating system.
3.5How an Operating System Organises Information
Introduction: Some of the OSs from Microsoft Corporation which is a software company are: Windows 8/10/NT/Me/XP/FD/VISTA. Others from various corporations are Linux, UNIX, Mac OS and OS/2. The following factors dictate how an Operating system organizes information: Rapid aces - the organization should allow quick access of stored data. Ease of update - the method should allow ease of update and the operating system should be able to keep a record of the date of modification. Economy of storage – the method should use the least storage possible because memory is a scarce resource.
Simplicity of maintenance – the method should enable quick navigation through the file system and make it easy for it to be maintained. Reliability - the file organization method should be reliable. Windows organize information in three tier hierarchy i.e; Files Folders and subfolders Drives.
1. File It’s a collection of related data or information given a unique name for ease of access, manipulation and storage on a backing storage and stored in one location a. A file has details that indicate:
- A unique name and an optional extension
- Its size, date and time the file was created or modified. Types of files There are three are types namely; system, application and data files. System files : contain information that is critical for the operation of the computer. Application files: these files hold programs or application files that are executable. Data files contain user specific data. The are some file extension; Extension File type Description .doc Data A Microsoft Word document file .txt Data A plain text file created using note pad or DOS editor. .exe Application file The file that launches a particular application e.g. PM 7.0 .exe, Winword.exe, etc .bat System files File containing a series of commands loaded during boot up. .sys System files System files that perform fundamental operation in a computer. Function of file
- Storage of data
- Organization of information
2. Folder / Directory It’s a named storage area where the user can store related files for easy access. All folders or directories originate from a special directory called the root directory or folder. The root directory is represented by a back slash (). Sub-folder is a folder or directory within another folder/directory. In Windows folders and sub- folders icon appear in yellow colour while file icons are mostly white with a fold at the top right hand corner. File icon Folder icon
Icons – are small images representing objects such as files, application programs, peripheral devices, operator tools in programs, etc. Are manipulated using pointing devices. Examples icons on the desktop are My Computer, Recycle bin, Internet Explorer, My Documents, Antivirus, etc The task bar A long bar that runs across the desktop. Enables the user to switch between programs and documents (tasks) that are currently running. It has three main parts: Start button: Left most button on the taskbar that the user clicks to display the start menu. Task manager: Plain stripe that displays buttons of all currently running tasks. System tray: Right most part of the taskbar. It has icons of the tasks running in the background but are not displayed on the screen e.g. Time and Calendar etc. To display the task simply double click its icon. The Start Menu When you click the Start button , a Start Menu appears which a list of choices is. When you click any choice in the Start Menu, the list of choices displayed is called Sidekick Menu. Common Start Menu Items: All Programs – which displays a list of all programs installed in the computer. Start Menu Task Manager System Tray Sidekick menu Start Menu
My Recent Documents – which lists the last 15 recently accessed files. Control Panel – provides tools which user can use to maintain and make changes to the computer setup. Control panel – provides options for you to customize the appearance and functionality of your computer, add or remove programs, and setup network connections and user accounts. My computer – give access to, and information about, the disk drives, cameras, scanners and other hardware connected to your computer. Search – opens a window where you can pick search options and work with search results incase the user forgets file or folder name or its location. Help and support – opens a central location for help topics, tutorials, troubleshooting and other support services.. Run – enables the user to: Install programs on the hard disk, open files and folders from a storage location, and Run programs from removable media. It also opens a program, folder document or a web site. Log on / log off: Log on is a security measure that restricts unauthorized users from accessing computer resources. It prompts the user for a User name and Password in order to gain access. After using the computer Log off the computer before leaving. Review Questions 3.
- Explain the following mouse concepts: a) Click b) Double click c) Drag and drop
- Define the following terms: a) Desktop b) Icon c) Sidekick menu d) Taskbar
- List and explain the three parts of a taskbar 4.Why is it important to first shut down the computer before you turn it off? 5.Explain how you would move the taskbar to the top of the desktop. 6.With the help of the teacher and a computer running Windows, customize the taskbar such that: a) The start menu is displayed in small icons. b) The clock is not displayed. c) The taskbar is hidden. d) A program is added on or removed from the start menu
3.8 Managing Files and Folders
Windows Explorer Lets the user display the drives and folders in a hierarchy or trees structure. The explorer divides the window into two panes.
Parts of an application window Title bar – displays the name of the current application program or task. Menu bar – provides a drop down list of commands that can used to manipulate tasks. Toolbars – are buttons of commands arranged in a row that are shortcuts to menu commands. Work area – is the working area where you can create your documents. Creating a new file To create a file for a specific application program installed in your computer proceed as follows: a. Display the Explorer Window b. From the From the folder tree on the left pane, select the location in which you want to create a new folder e.g. Local C, 3 ½ etc c. From File menu, click New then select the Application Program e.g Microsoft Word, Microsoft Excel Worksheet etc.. A new file with a temporary name of the application appears on the right pane. d. Type a new name for the file to replace the temporary name then press enter. To work in the file double click and the application program opens, as shown in the figure below. Menu bar Toolbar Status bar Work area
NB: A file can be contained in a folder or subfolder and subfolder and a file can be contained in the same folder. Renaming Files and folders Renaming is changing the original name to a new name. To rename right click the file or folder icon then select rename. Type a new name to replace the existing. Sorting files and folders Refers to organizing files and folders in a particular way. To sort select the location, or folder then in the View menu select Arrange Icon by option to choose either by name, size, type or date modified. Deleting files and folders When you delete an item from the hard disk, it is temporary held in the recycle bin. Recycle bin is a special folder which temporarily holds items deleted from the hard disk. NB: Items deleted from removable storage devices are not held in the recycle bin and are completely lost. Don’t attempt to delete system and application files from the hard disk. To delete file or folder In the folder tree, right click the file or folder and then select delete from the shortcut menu. NB: Holding down Shift key as you command delete, the deleted file or folder is completely discarded bypassing the Recyclebin folder. Restoring deleted files and folders double click the Recycle bin icon
b) Sort files c) Copy d) Move e) Delete 6 Of the five commands in Question5, which two must be used with a lot of caution when manipulating files? 7 Briefly explain the importance of each part of a window 8 Why is it important to give descriptive names to file or a folder 9 Draw a directory tree showing how files and folders are organized by an operating system. 10 Explain how you would: a. Minimize b. Close and exit an application window. c. Move a window from one location to another. d. Access the folder/the directory tree.
