define system calls, Operating System

 

When a computer is started on, the program that executed first is named the ''operating system.'' It controls pretty much all applications in the computer. This adds who logs in, how disks are consumed, how memory is accessed, how the CPU is used.

The way that applications talk to the operating system is via ''system calls.'' A system call seems like a procedure call, but it's not same -- it is a request to the operating system to operate some application.

There are 5 basic system calls that Unix gives for file I/O.

        1.  int open(char *path, int flags [ , int mode ] );

        2.  int close(int fd);

        3.  int read(int fd, char *buf, int size);

        4.  int write(int fd, char *buf, int size);

        5.  off_t lseek(int fd, off_t offset, int whence);

The reason the operating system operates I/O is for safety -- the computer has to ensure that if my program has a exception in it, then it doesn't affect the system, and it doesn't collide other people's applications that can be running at later or the same time. Whenever you do screen or disk or network I/O, you have to go through the operating system and use system calls.

 

 

 

1541_System calls.png

Posted Date: 7/28/2012 8:12:03 AM | Location : United States







Related Discussions:- define system calls, Assignment Help, Ask Question on define system calls, Get Answer, Expert's Help, define system calls Discussions

Write discussion on define system calls
Your posts are moderated
Related Questions
what is deadlock

Grouping Threads That Execute Similar Functions   Thread Groups are generally used to group threads that execute similar functions of the application program. For instance, if

Extend task 1 so that the requests are issued by the clients instead of the server. The server now do not use the "all_requests.dat" file. Instead every client thread reads from

What do you mean by semaphore?  Semaphore : A synchronization variable that acquires on positive integer values. Invented by the Dijkstra P (semaphore): an atomic proce

What is an acyclic graph? A tree that has been corrupted by links to other branches, but does not have any cyclic paths in it.

Unix process API The two most important function calls to use when programming with several processes are fork and exec:  fork() creates a copy of current process. It gives

What is an operating system? An operating system is a program that acts as a mediator between a user and the computer hardware. The function of an operating system is to provid

Q. Define Input - Output operations? Serial lines, Disks, tapes and other devices should be communicated with at a very low level. The user require only specify the device and

What is a reference string? An algorithm is evaluated by running it on a particular string of memory references and computing the number of page faults. The string of memory re

explain simple segmentation