JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV REAL-TIME SYSTEMS Previous Question Paper (December - 2020 - R16)

While Linux and UNIX share a similar architecture and command-line interface, they differ significantly in their origin, licensing, and development model:

• Origin: UNIX was developed by AT&T Bell Labs in the 1970s as a proprietary operating system. Linux was created by Linus Torvalds in 1991 as a free, open-source clone of UNIX.
• Licensing: UNIX is a proprietary, copyrighted operating system owned by various vendors (e.g., IBM, Oracle). Linux is released under the GNU General Public License (GPL), making its source code freely available for modification and redistribution.
• Development: UNIX development is typically restricted to the vendor's internal teams. Linux is developed collaboratively by a global community of volunteers and corporate contributors.
• Portability: UNIX was originally designed for specific hardware architectures. Linux is highly portable and runs on a vast range of hardware, from embedded systems to supercomputers.
• Cost: UNIX usually requires a paid license for commercial use. Linux is generally free to use, though enterprise support versions may have associated costs.

The fork() system call is used to create a new process, known as the child process, which is an exact duplicate of the parent process. After the call, both processes continue execution from the next instruction. The function returns 0 to the child process and the process ID (PID) of the child to the parent process.

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>

int main() {
    pid_t pid = fork();
    if (pid < 0) {
        printf("Fork failed\n");
    } else if (pid == 0) {
        printf("Child process: PID = %d\n", getpid());
    } else {
        printf("Parent process: Created child with PID = %d\n", pid);
    }
    return 0;
}

In this program, the fork() call splits the execution flow. The parent process receives the child's PID and prints its branch, while the child process receives 0 and executes its own branch.