OPERATING SYSTEM An operating system is a group of computer programs that coordinates all the activities among computer hardware devices. It is the first program loaded into the computer by a boot program and remains in memory at all times. In other words, it’s what runs your computer

Functions of an Operating system 1. Processor Management duty of processor to different tasks being performed by the computer system. 2. Memory Management allocation of main memory and other storage areas to the system programs as well as user programs and data. 3. Input/output Management coordination and assignment of the different output and input device while one or more programs are being executed.

4. File Management the storage of file of various storage devices to another. It also allows all files to be easily changed and modified through the use of text editors or some other files manipulation routines. 5. Establishment and enforcement of a priority system. it determines and maintains the order in which jobs are to be executed in the computer system. 6. Automatic transition from job to job as directed by special control statements. 7. Interpretation of commands and instructions. 8. Coordination and assignment of compilers, assemblers, utility programs, and other software to the various user of the computer system. 9. Facilities easy communication between the computer system and the computer operator (human). It also establishes data security and integrity.

Components of Operating system The kernel, which represents the operating system's basic functions such as management of memory, processes, files, main inputs/outputs and communication functionalities. The shell, allowing communication with the operating system via a control language, letting the user control the peripherals without knowing the characteristics of the hardware used, management of physical addresses, etc. The file system, allowing files to be recorded in a tree structure. 

4 Types of Operating System Real-Time Operating System (RTOS) Single-User, Single Task Single-User, Multi-Tasking Multi-User

Real time Operating System (RTOS) Used to run computers embedded in machinery, robots, scientific instruments and industrial systems. Typically, it has little user interaction capability, and no end-user utilities, since the system will be a "sealed box" when delivered for use. An important part of an RTOS is managing the resources of the computer so that a particular operation executes in precisely the same amount of time every time it occurs Examples: Wind River, QNX, Real-time Linux, Real-time Windows NT

Single-User, Single Task   OS designed to manage the computer so that one user can effectively do one thing at a time The Palm OS used in many palmtop computers (PDA's) is an example of a single-user, single-task OS 59

Single-User, Multi-Tasking Lets a single user interact with several programs, simultaneously Most popular OS Used by most all PC's and Laptops Examples: Windows, Mac OS, Linux

Multi-User A multi-user OS allows many users to take advantage of the computer's resources, simultaneously The OS must make sure that the requirements of the various users are balanced, and that the programs they are using each have sufficient and separate resources so that a problem with one user doesn't affect any of the other users. Examples: Linux, Unix, VMS and mainframe OS, such as MVS

Examples of Operating System Windows 7, Vista, XP Mac OS Unix Linux Embedded Operating system

Advantages of Operating System Easy to use User friendly Intermediate between all hardware and software of the system

Disadvantages of Operating System If any problems affected in OS, you may lose all the contents which have been stored already Unwanted user can use your own system Compatibility