convention to use these names. In C++, the names are to be taken literally, and the "void" in the parameter list is to be omitted, if strict conformance is desired. Other platform-dependent formats are also allowed by the C and C++ standards, except that in C++ the return type must always be int; for example, Unix (though not POSIX.1) and Windows have a third argument giving the program's environment, otherwise accessible through getenv in stdlib.h: int main(int argc, char **argv, char **envp); Darwin-based operating systems, such as macOS, have a fourth parameter containing arbitrary OS-supplied information, such as the path to the executing binary: int main(int argc, char **argv, char **envp, char **apple); The value returned from the main function becomes the exit status of the process, though the C standard only ascribes specific meaning to two values: EXIT_SUCCESS (traditionally 0) and EXIT_FAILURE. The meaning of other possible return values is implementation-defined. In case a return value is not defined by the programmer, an implicit return 0; at the end of the main() function is inserted by the compiler; this behavior is required by the C++ standard. It is guaranteed that argc is non-negative and that argv[argc] is a null pointer. By convention, the command-line arguments specified by argc and argv include the name of the program as the first element if argc is greater than 0; if a user types a command of "rm file", the shell will initialise the rm process with argc = 2 and argv = {"rm", "file", NULL}. As argv[0] is the name that processes appear under in ps, top etc., some programs, such as daemons or those running within an interpreter or virtual machine (where argv[0] would be the name of the host executable), may choose to alter their argv to give a more descriptive argv[0], usually by means of the exec system call. The main() function is special; normally every C and C++ program must define it exactly once. If declared, main() must be declared as if it has external linkage; it cannot be declared static or inline. In C++, main() must be in the global namespace (i.e. ::main), cannot be overloaded, and cannot be a member function, although the name is not otherwise reserved, and may be used for member functions, classes, enumerations, or non-member functions in other namespaces. In C++ (unlike C) main() cannot be called recursively and cannot have its