Lesson 4 0x004 100. Operating Systems. Topics. OS Definition Types of PC OS Functions of OS Terms and Concepts DOS Commands. Operating Systems. Operating System
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Lesson 4 0x004100 Operating Systems
Topics • OS Definition • Types of PC OS • Functions of OS • Terms and Concepts • DOS Commands
Operating Systems • Operating System • Is a set of programs which manage all operations of the computer system, and enables the user to interact with the hardware ‘HW’. • It provides a consistent environment for other software to execute commands.
Examples of PC OS Microsoft Windows Me, NT, 2000, XP, Vista, 7, 8 (Client) Windows 2000, 2003 , 2008, 2012 (Server ) Windows 98 Macintosh Mac OS X snow Leopard Mac OS X Lion Mac OS X Mountain Lion
Examples of PC OS (Cont.) Chrome OS Linux OS/2
Examples of Mobile Devices OS Mobiles OS -iOS 5 -iOS 6 -iOS 7 -Android 4 Ice Cream Sandwich -Android 4.2Jelly Beans -Android 4.3 Kit Kat Microsoft -Windows 7 m -Windows 8 m
Functions of the operating systems • Input and output: allows computer to display and get data from the I/O devices to interact with users. • Memory and secondary storage management: • allows the user to organize their data on secondary storage into files & folders • alsomanagesthe use of main memory by splittingmain memory into two parts (user area, system area). • Time sharing: operating system can allow more than one user to work on the same computer, and run more than one program at the same time.
Functions of the operating systems (cont.) Communication: it is the ability to a computer to communicate with other computers to transfer programs and data. Accounting: this is to keep track of what each user has done on the computer, to bill each for the resources used(if necessary). (for each user a separate account). Program Execution Environment : OS loads the program into the memory and manage program execution Security: make sure that only authorized users can access computer.
Functions of the operating systems as a diagram Input/Output Memory and storage Management Operating System Security Time Sharing Program Execution Environment Communication Accounting
Components of an operating system • The Executive or Supervisor • The Command Interpreter • The Internal Commands • The External Commands
Components of an operating system • (1) The executive or supervisor: • this is the main part of the operating system. • it is a memory resident program which stays in RAM as long as the computer is on. • it supervises all operations like data storage and memory access. • The supervisor is loaded into main memory at switch-on time by a small program in ROM called the Bootstrap loader. this program looks for the supervisor program on the first track on the disk(boot sector). It loads the supervisor into the ram and runs it, this process is called(Booting the system).
Components of an operating system (cont.) • (2) The command interpreter: • each operating system has a set of commands, each command has a valid syntax. • the command interpreter interprets each command issued by the user and calls for the appropriate program from the operating system to carry out the command. • If there is a syntax error, it will notify the user and may lead the user how to handle it.
Components of an operating system (cont.) • (3) The internal commands: • those are the mostly used commands set, they remain in the ram. • Examples: Dir, Cd, Ren, …etc. • (4) The external commands: • Large and less frequently used commands. • They kept in the disk to save the ram space, they will be loaded in ram once they are used. • Examples: Format, Diskcopy, Fdisk ..etc
OS Terms and Concepts • Graphical User Interface GUI: • The method by which a person communicates with a computer. It uses a mouse, touch pad, icons to interact with the computer. • Shell: • A program that runs on top of the OS and allows the user to issue commands through a set of menus or GUI. • Networking Operating System NOS: • Similar to a standard OS, except that the NOS is optimized to provide services to other machines on the network.
OS Terms and Concepts • Cooperative Multitasking: • A multitasking method that depends on the application itself to be responsible for using and then freeing access to the processor. • Preemptive Multitasking: • A multitasking method in which the OS allots each application a certain amount of processor time and then forcibly takes back control and gives another application or task access to the processor. • Multithreading: • The ability of a single application to have multiple requests in to the processor at one time.
OS Terms and Concepts • Virtual Memory ( swapping or paging file): A+ book p53 How • It uses what is called a swap file, or paging file. • A swap file is actually hard drive space into which idle pieces of programs are placed, while other active parts of programs are kept/swapped into main memory ( RAM). Why • Modern applications requires huge memory to run. • Also a lot of programs can work at the same time, so virtual memory takes the advantage of the vast nature of recent computer programs. Disadvantages • The disadvantage here is that it is not as fast as the real memory.