What is system calls in os?  

system call - a feature built into an application program that requests a service from the operating system, as when a word processing program requests the use of the printer to print a document.

Answered by Nishu%27s , an ibibo Master, at 9:50 PM on November 24, 2008

A system call is a request made by any arbitrary program to the kernel for performing tasks -- picked from a predefined set -- which the said program does not have required permissions to execute in its own flow of execution. System calls provide the interface between a process and the kernel. These calls are generally available as assembly language instructions and they are usually listed in the various manuals used by the assembly-language programmers. Most operations interacting with the system require permissions not available to a user level process, i.e. any I/O performed with any arbitrary device present on the system or any form of communication with other processes requires the use of system calls.

Answered by Kamlesh B , an ibibo Specialist, at 6:49 PM on November 24, 2008

A System Call is a frequently used low level operating system function, available to programmers as functions in high-level languages, to ask the operating system to perform a service such as memory allocation or device I/O.

For example, all operating systems have a routine for creating a directory. If you want to execute an operating system routine from a program, you must make a system call.

Answered by Suparna , an ibibo Master, at 6:30 PM on November 24, 2008

Hi
system call in os is refered to the communication between the components of os.
ex- if we have to copy and paste to new place.
first we will copy..then we will paste it to the destination place.
sometimes, we get an message that "there is a file/folder with this name already exist ".

how it happens, have u ever think this, how do they know for this..these are the system calls which communicate with the processor and memory which trransfer information about ur process .

bye and best of lcuk

Answered by Abhishek , an ibibo Advisor, at 3:26 PM on November 24, 2008