Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
OPERATING SYSTEMS The various hardware pieces that are assembled by an organization to enhance its computerized accounting information systems need an operating system, which is “…an integrated system of programs that manages the operations of the CPU, controls the input/output and storage resources and activities of the computer system, and provides various support services as the computer executes the application programs of users.”(O’Brien, 2004:508). Hove,Mutungwazi and Totev(1996:59) adds that OS is “…a piece of computer software which intermediates between the user and machine(hardware). It is part of the control software.” And “…a master control program which controls the functions of a computer system as a whole and the running of application programs.” (Anderson, 1994:399) The operating system is part of the software a computer uses in conjunction with / interfacing the user and the two are the most important part of the computer system, “No matter how state-of-the-art the computer is, it is of little value without the right software.” (Bodnar and Hopwood, 1998:120) In fact it is best to select the software before selecting the hardware. The software is made up of three categories: operating systems and their extensions; user application programs and computer languages (translator). The purpose of an OS is : to maximize productivity of a computer system by operating it in the most efficient manner. To minimize the amount of human intervention during processing, To assist in accessing a network, data capture, saving and retrieving files, printing/displaying output To boot and activate the computer system before operations. Exhibit 1.1 shows OS: End-users Application Software/ Program Operating System/ System Software Hardware Operating System/ System Software Application Software/ Program End-users Adapted from (O’Brien, 2004:510 and Bodnar and Hopewood, 1998: 120) The OS embraces the hardware with the application program in between the hardware and end-users. Users are directly involved in the design of systems so they need to understand which programs are easy or difficult to use, (Lucas, 1997: 202) As an enduser, the application program you use e.g Pastel, is controlled by the OS whose functions are three according to (Bodnar and Hopewood, 1998) or five according to (O’Brien, 2004:510). These are: accounting and security, management and allocation of computer system resources; and software services to user application programs. O’Brien’s five functions are: providing a user interface, resource management, task management, file management, utilities and support services. User interface: Allows user to communicate with OS enabling user to load programs, access files, do other tasks eg. Command-driven, menu-driven, graphical user interface (GUI) i.e. the trend is , “… moving away from the entry of brief end-user commands …or selection of choices from menus of options.” The trend is on use of “icons, bars, buttons, boxes and similar images.” GUis rely on pointing devices eg. Electronic mouse, touch pad. Resource management: OS uses resource management programs to manage the hardware and networking resources of a computer system i.e its CPU, memory, secondary storage devices, tele-communication processors and input/output peripherals. It incorporates accounting and security of the whole system. For most multi-users, OS, have securityto limit “access to the system and its resources, protects files, and …memory.” (Bodnar and Hopewood, 1998:120). Each user is assigned a user account allowing user to log on /log out, by use of a user account number or user I.D. and log-on password. When logged on, the system monitors, records and limits the activities of the user. Its like an Audit trail. Systems personnel create these user accounts and pre-define user limits e.g what resources are available to users such as: i) Maximum amount of disk storage user can use ii) Maximum number of files user can create iii) Maximum number of lines or pages user can print iv) Maximum amount of CPU time user can use v) Maximum amount of primary memory available to user. It further limits user on: a) Access to magnetic tape drives b) Access to particular files or programs. File management: In terms of security levels, users are assigned levels, eg 1-10 with 1 being the highest level, 10 the lowest level. Security level number 4 enjoys what security level number 5 can do but security level number 4 may not have privileges due to 5. File creation and protection are included in the security system eg. “…a user can create, modify and erase files.” (Bodnar and Hopewood,1998:121).eg: Public files allows any user access to file, while private files allow no one else access to file; and semi-private files allows some users with the correct password access to files. User also specifies if others can or cannot modify, erase these accessible files. Hence the OS keeps “directories of information about the location and characteristics of files stored on a computer’s secondary storage devices.” (O’Brien, 2004: 511) Task management: The OS manages “ the accomplishment of computing tasks of endusers.” Each task is given a slice of a CPU’s time and swapping of other tasks with those that are allocated time to allow for “concurrent processing” in a multi-programming and or time sharing set up. (Bodnar and Hopewood, 1998:121) Time sharing allows”more than one user to concurrently interact with or execute programs on the computer.” Task management involves a “multi-tasking capability where several computing tasks can occur at the same time.” Efficiency of multi-tasking depends on “the processing power of a CPU and the virtual memory and multi-tasking capabilities of the OS it uses.” Hence we find that microcomputers, mid-range, mainframe OS have multi-tasking capabilities. Response time of the system is affected by the number of users demanding use of the CPU hence there is a slow down of the CPU felt by users. You have complained of a slow response time of the Internet at one time. Its because there are too many users using the sever at once. Another example of multi-tasking is “ concurrent execution” of more than one program. When you open an Excel file, are researching on Google and typing a report on WordPerfect, it is concurrent execution. These are windows (Bodnar and Hopewood,1998: 122) that appear on the VDU. In the foreground task is the active program while those programs not being executed are in the background task. Popular Operating Systems: Windows 2000 Microsoft, Solaris 8 UNIX, Netware 5.1 Novel and Linux 6.1 Red Hat Software. Computer languages. According to Lucas (1997: 203) software generations are as follows: Software generation First Period Software 1950-58 Second 1958-64 Third 1964-70 Fourth 1970-80 Machine language, assembly language where binary codes unique to each computer were used Assembly language which reduced difficulties in writing machine language, used translator language called assemblers which allowed computers to convert the instructions of such language into machine instruction a.k.a symbolic languages as symbols are used or mnemonics ( memory aids) to represent codes, storage locations, data elements. High level languages, batch OS, dedicated on-line systems and experimental time-sharing were developed. Preponderance of higher-level languages, expansion of packaged systems, OS mandatory, mixed on-line and batch applications, virtual memory, time-sharing systems. Has less rigid rules, forms and syntaxes, instructions are called statements. Each macro-instruction generates several machine instructions through use of computers/ interpreters. Non-procedural and conversational than prior languages. Users and programmers specify what outcome they want; natural languages are 4GLs that are close to English/ human languages; linked to Artificial Intelligence, virtual memory OS program for PCs, Object oriented languages, Open systems.