Operating System
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Operating System is a program, which acts as an interface between the user of computer and the computer hardware. the operating system can be viewed as a set of software programs, normally supplied along with hardware for the effective and easy use of the machine. examples - Linux,Microsoft Windows,Android.
The Main Functions of an Operating System
- Operating system is to make the hardware convinient to use.
- Operating system help user to execute programs.
- Operating system control execution of program to stop errors and improper use of computer System.
- Operating system give security to information of users.
- Operating system give facility to share the same hardware among the users.
- Information Management
- Process Management
- Memory Management
Information Management
Information management provides the facility to store, retrieve, modify or remove the information on file and directories. These system servies manage the organization of information into files and directories by allocating memory space to them. It also ensures that correct programs have access to information, have occupied memory space and driving various devices. Some of the services provided under Information management are:
- Create a file.
- Create a directory.
- Open a file for read or write purposes.
- Explore a directory.
- Close a file.
- Read data from file to buffer.
- Write data from buffer to file.
- Move file pointer.
- Create a link.
- Chang working directory.
In multi-user operating system, a number of user, at different terminal of a network, may execute same or different programs at a time. But such a computer system has only one C.P.U. and it can execute one instruction at same time. The process management of operating system keep the track of all running programs called process. the process management module of single user operating system are less complicated then multi-user operating system. The services provided under process management are:
- Read a process.
- Block a process.
- Resume a process.
- terminate a process.
- suspend a process .
- delay a process.
- Change a priority of a process.
- Genrate a process.
When a job is to be executed, the operating system loads the job in main memory from disk. But before loading it in memory, it should know that how much of free memory is avaliable and how much of memory should be allocated to the job. For this, the operating system keeps list of all free memory location. before a program is loaded in the memory the operating system consults with this list. When the program is executed complete, it remove program from main memory and again modify the list.
The system call in it are:
- To allocate a chunk of memory to a process.
- To free chunk of memory from a process.
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