The statements of the function are inside the curly braces. When there is a function call in the program, that specific function gets the control and is executed. Furthermore, after executing the function, the control passes back to the main program. A system call is a function provided by the kernel to enter kernel mode to access a resource while a function call is a request made by a program or script that execute a predetermined function.
Thus, this is the main difference between system call and function call. Also, another difference between system call and function call is the context switching. Context switching occurs in system calls; however, there is no context switching occurrence in function calls. System calls allow the program to access memory or a hardware resource from the kernel while function calls help to pass the control to a specific function and to execute the defined task.
Hence, this is the functional difference between system call and function call. In brief, system calls are associated with kernel mode while function calls are associated with user mode. This type of situation occurs when a parent process creates a child process, and the execution of the parent process remains suspended until its child process executes.
The suspension of the parent process automatically occurs with a wait system call. When the child process ends execution, the control moves back to the parent process. Processes use this system call to create processes that are a copy of themselves. With the help of this system Call parent process creates a child process, and the execution of the parent process will be suspended till the child process executes.
This system call runs when an executable file in the context of an already running process that replaces the older executable file. However, the original process identifier remains as a new process is not built, but stack, data, head, data, etc. The kill system call is used by OS to send a termination signal to a process that urges the process to exit.
However, a kill system call does not necessarily mean killing the process and can have various meanings. A system call is a request made by the program to enter into kernel mode to access a process.. A library call is a request made by the program to access a library function defined in a programming library.
In kernel mode the programs are directly accessible to the memory and hardware resources. In user mode, the programs cannot directly accessible to the memory and hardware resources. In system call, the mode is executed or switches from user mode to Kernel mode.
In library call, the mode is executed in user mode only. In system call the execution process speed is slower than the library call because there is a mode of transition called context switching. In library call the execution process speed is faster than the system call because there is no mode of context switching.
A system call is a function provided by the kernel to enter into the kernel mode to access the hardware resources. A Library call is a function provided by the programming library to perform a task. System call are the entry points of the kernel, and therefore they are not linked to the program. Library functions are linked into your program. A system call is not portable.
System call provides an interface between the process and the Operating System. System call allows user-level process to request some services from the OS which process itself is not allowed to do.
In handling the trap, the OS will enter in the kernel mode, where it has access to privileged instructions, can perform the desired services on behalf of user-level process.
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