One process is created to start executing the program. When the fork( ) system call is executed, another process is created. The original process is called the parent process and the second process is called the child process.

fork() in C Fork system call is used for creating a new process, which is called child process, which runs concurrently with the process that makes the fork() call (parent process). After a new child process is created, both processes will execute the next instruction following the fork() system call.

A child process is a process created by a parent process in operating system using a fork() system call. A child process is created as its parent process’s copy and inherits most of its attributes. If a child process has no parent process, it was created directly by the kernel.

If the parent and child keep executing the same code (i.e. they don’t check the return value of fork() , or their own process ID, and branch to different code paths based on it), then each subsequent fork will double the number of processes. So, yes, after three forks, you will end up with 2³ = 8 processes in total./span>

The fork() function will fail if: [EAGAIN] The system lacked the necessary resources to create another process, or the system-imposed limit on the total number of processes under execution system-wide or by a single user {CHILD_MAX} would be exceeded.

A system call is a call to a function that is not part of the application but is inside the kernel. So, you can understand printf() as a function that convert your data into a formatted sequence of bytes and that calls write() to write those bytes onto the output. But C++ gives you cout ; Java System. out./span>

There are 5 different categories of system calls: process control, file manipulation, device manipulation, information maintenance, and communication.

In modern POSIX compliant operating systems, a program that needs to access data from a file stored in a file system uses the read system call. The file is identified by a file descriptor that is normally obtained from a previous call to open.

fopen is a function call. A system call interacts with the underlying OS, which manages resources. Its orders of magnitud more expensive than a function call, because many steps have to be taken to preserve the state of the process that made the syscall./span>

System calls are usually made when a process in user mode requires access to a resource. Then the system call is executed on a priority basis in the kernel mode. After the execution of the system call, the control returns to the user mode and execution of user processes can be resumed./span>

Although the two terms are used interchangeably, there is a difference between system call and function call. System calls are used when a program needs to communicate with the kernel while function calls are used to call a specific function within the program./span>

System call is a call to a subroutine built in to the system, while a function call is a call to a subroutine within the program. Unlike function calls, system calls are used when a program needs to perform some task, which it does not have privilege for.

System calls provide an essential interface between a process and the operating system. In most systems, system calls can only be made from userspace processes, while in some systems, OS/360 and successors for example, privileged system code also issues system calls.

System call provides the services of the operating system to the user programs via Application Program Interface(API). It provides an interface between a process and operating system to allow user-level processes to request services of the operating system. System calls are the only entry points into the kernel system./span>

A system call requires that the system switches from User mode to Kernel mode. This makes system calls expensive./span>

A system call does not necessarily require a context switch in general, but rather a privilege switch. This is because the kernel memory is mapped in each process memory. On some systems, like micro-kernels, a system call may involve a context switch because drivers are in a different process./span>

The system call is the fundamental interface between an application and the Linux kernel. System calls and library wrapper functions System calls are generally not invoked directly, but rather via wrapper functions in glibc (or perhaps some other library)./span>

A context switch can also occur as the result of an interrupt, such as when a task needs to access disk storage, freeing up CPU time for other tasks. Some operating systems also require a context switch to move between user mode and kernel mode tasks.

When we switch between two threads, on the other hand, it is not needed to invalidate the TLB because all threads share the same address space, and thus have the same contents in the cache. Thus context switching between two kernel threads is slightly faster than switching between two processes.

So, a mode switch is switch of the mode of a single process. Context Switch – It is when the running process current state is stored some place and a new process is chosen for running and its already stored state is loaded in the CPU registers./span>

Context Switching involves storing the context or state of a process so that it can be reloaded when required and execution can be resumed from the same point as earlier. This is a feature of a multitasking operating system and allows a single CPU to be shared by multiple processes./span>

A context switching is a process that involves switching of the CPU from one process or task to another. In this phenomenon, the execution of the process that is present in the running state is suspended by the kernel and another process that is present in the ready state is executed by the CPU./span>

Context switching allows for one CPU to handle numerous processes or threads without the need for additional processors. Any operating system that allows for multitasking relies heavily on the use of context switching to allow different processes to run at the same time./span>

The key reason context switching is bad is because it takes time and effort to get into focus. So every time we switch tasks, we lose energy that we wouldn’t have lost if we had just stayed on one task./span>