Chapter 1, defined a process as an "execution context." By this we mean the collection of information needed to carry on a specific computation; it includes the pages accessed, the open files, the hardware register contents, and so on. An executable file is a regular file that describes how to initialize a new execution context, i.e., how to start a new computation.
Suppose a user wants to list the files in the current directory: he knows that this result can be simply achieved by typing the filename of the /bin/ls external command at the shell prompt. The command shell forks a new process, which in turn invokes an execve( ) system call (see Section 19.4 later in this chapter), passing as one of its parameters a string including the full pathname for the ls executable file, /bin/ls in this case. The sys_execve( ) service routine finds the corresponding file, checks the executable format, and modifies the execution context of the current process according to the information stored in it. As a result, when the system call terminates, the process starts executing the code stored in the executable file, which performs the directory listing.
 The pathnames of executable files are not fixed in Linux; they depend on the distribution used. Several standard naming schemes such as FHS and FSSTND have been proposed for all Unix systems.
When a process starts running a new program, its execution context changes drastically since most of the resources obtained during ...