System call is an interface between a running program and operating system. It allows user to access services provided by operating system. This system calls are procedures written using C, C++ and assembly language instructions. Each operating system has its own name for each system call.
1. Each system call associated with a particular number.
2. System call interface maintains a table indexed according to these numbers.
3. The system call interface invokes intended system call in operating system kernel and returns status of the system call and any return values.
4. The caller needs to know nothing about how the system call isimplemented. Just needs to obey API and understand what OS will doas a result call.
5. Most details of operating system interface hidden from programmersby API. It is managed by run-time support library.
Open ( ) system call for most file systems, a program initializes access to a file in a file system using the open system call. This allocates resources associated to the file (the file descriptor), and returns a handle that the process will use to refer to that file.
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