How does the operating system initiate the launch of an executable program?

The operating system initiates the execution of a program through a system call, usually the exec family of functions in Unix-like systems or CreateProcess in Windows.

The process of launching includes the following steps:

1. Loading the executable file into memory.
2. Creating a new process or replacing the current process with a new image.
3. Initializing the execution context (registers, stack, memory segments).
4. Transferring control to the program's entry point (for example, the main function in C/C++).

For example, in Unix:

pid_t pid = fork(); // create a new process
if (pid == 0) {
    execl("./program", "program", NULL); // load and run the program
}

Thus, the OS manages resources and ensures process isolation when launching programs.