Types of Services in Operating Systems

 Operating  System provides certain services to the programs and to the users. there are following three major types of services.

      1) Information Management

      2) Process Management

      3) Memory Management

1- Information Management  

It refers to a set of services used for storing , retrieving , modifying or removing the information on various devices. It manages the organization of information in terms of directories and files, allocating , deallocating, the sectors to various files ensuring right people have access to information and driving various devices.

Some of the System calls in this category are as follows:

1)Create a file                                                                                                                          6) Move the file pointer.

2) Crete a Directory                                                                                                                  7) Read and return file's status.

3) Open a File                                                                                                                            8) Create a link.

4) Close a file                                                                                                                             9) change working directory .

5) Read data from file to buffer                                                                                               10) Write data from buffer to file .  

2 - Process Management  

 If operating system supports multiple users than services under this are very important . In this regard operating systems has to keep track of all the completing processes , Schedule them, dispatch them one after another. But user should feel that he has the full control of the CPU.

some of the systems calls in this category are as follows.

1) create a child process  identical to the parent.

2) Terminate a process

3) Wait for a child process to terminate

4) Change the priority of process

5) Block the process

6) Ready the process

7) Dispatch a process

8) Suspend a process

9) Resume a process

10 ) Delay a process

11) Fork a process

3- Memory Management

 The services provided under memory management are directed to keeping track of memory and allocating , deallocating it to various process. The operating Systems keeps a list free memory locations. Before a program is loaded in memory from the disk , this module consults this free list, allocates the memory to the process, depending upon program size and updates the list of free memory.

some of the systems calls in this category are as follows:

1) Allocate a chunk of memory to process

2) Free a chunk of memory from a process.