System Calls

System Calls-System calls provide an interface to the services made available by an operating
system or interface between a pEocess and the operating system.the purpose of a system call is to request the operating system to perform some activity. For ex writing a  simple program to read data from one file and copy them to another file. The first input that the program will need is the names of the two files: the input file and the output file.This requires many I/O system calls.Once the two file names are obtained, the program must open the input file and create the output file.Each of these operations requires another system call.
 
  There are different system calls for performing different kinds of tasks -
•File manipulation system calls for example, are open, close, read, write, lseek etc.
•There can be system calls for process control. These can be like abort, execute, create
    process, terminate a process, allocate and free ‘memory for a process etc.
•For device management, the system calls that can be there are — request device, release:
device, read, write, reposition, get and set device attributes etc
•For managing the information, the system calls that can be there are — get and set
time, get and set file or device attributes etc.. ‘‘