TERM2 WEEK/PERIOD: 3 CLASS: SS1 TOPIC:OPERATING SYSTEM

CONTENT An operating system is a set of program which takes over the operation of the computer to the point of being able to allow a number of programs to be run on the computer without human intervention. Part of it stays in the core of the storage permanently, during the running of the computer. This part is known as the Executive Supervisor or kernel. The other parts, which are required less frequently are often held on a direct access storage device (disk) and called into the main memory when needed. Functions of the Operating System 1. It serves as a communication link between computer and the console terminal 2. It has control over selection and operation of input/output devices and filled handling 3. Does scheduling and loading of jobs in order to provide for continuous processing 4. Control system security by monitoring the use of passwords 5. It facilitates passing of control from one program to another without human intervention 6. It provide a complete record of all that happens during processing in form of a log 7. Helps programs to run Types of Operating System 1. Single program System: This permits only one user’s program to be in the main storage and processed at a time. It is available on micro-computers based system. Examples are MS-DOS, PC –DOS, 2. Simple Batch System: This provides for multi-programming but it has few facilities for interaction or multi-access 3. Multi access and Time sharing System: This system permits a number of users to access and use the computer at the same time. On larger micro computers as well as the smaller the smaller mini computers are a number of operating systems which are available for use e.g UNIX example is the OS/400 produced by IBM for use on the AS/400 super mini. Examples of Operating System can be looked at from two perspectives: 1. Command line (MS-DOS) Microsoft Disk OS: It was the main operating system for IBM pc personal computer during 1980 up to the mid 1990, until it was gradually overshadowed by operating systems offering a Graphical User Interface(GUI), in particular by various generations of the Microsoft windows OS. 2. Graphical User Interface (GUI) Examples of GUI are windows 95/98/2000/xp. Dos commands: A command instruction given to the computer to perform a specific task. DOS commands are grouped into two: internal and external commands. Internal commands are loaded into the computer memory during booting. They reside on the disk. UNIX: UNIX is widely used in both servers and work stations and mobile devices. UNIX was designed to be portable portable, capable of performing multi tasks and time sharing. MICROSOFT WINDOWS: All versions of Microsoft windows have had an MS-DOS like command Line Interface (CLI) Examples of GUI: Windows 95/98/2000/xp: Microsoft windows are series of software operating systems and graphical user interface produced by Microsoft. LINUS: Linus is an Operating System created hobby, by a young student, Linus Torvalds. It uses home and office desktop operating system. In addition to its adaptability and robustness, it is main alternative for proprietary UNIX and Microsoft OS. TRANSLATORS A translator is a system program that translates written high level language into a machine language. The statements in high level language are called source program. The statements in the machine language are called object program. Examples of Translators I. Assembler II. Compiler III. Interpreters UTILITY PROGRAMS Utility software is a kind of program designed to help, analyze, configure, optimize and maintain the computer. The main types include: Sort, Editors, File copying, Dump, File maintenances, Tracing and debugging