A program shall contain a global function named
main, which is the designated start of the program.
|argc||-||Non-negative value representing the number of arguments passed to the program from the environment in which the program is run.|
|argv||-||Pointer to the first element of an array of pointers to null-terminated multibyte strings that represent the arguments passed to the program from the execution environment (argv through argv[argc-1]). The value of argv[argc] is guaranteed to be 0.|
|body||-||The body of the main function|
|other_parameters||-|| Implementations may allow additional forms of the main function as long as the return type remains
argv are arbitrary, as well as the representation of the types of the parameters: int main(int ac, char** av) is equally valid.
main function is called at program startup after initialization of the non-local objects with static storage duration. It is the designated entry point to a program that is executed in hosted environment (that is, with an operating system). The entry points to freestanding programs (boot loaders, OS kernels, etc) are implementation-defined.
The parameters of the two-parameter form of the main function allow arbitrary multibyte character strings to be passed from the execution environment (these are typically known as command line arguments), the pointers
argv .. argv[argc-1] point at the first characters in each of these strings.
argv is the pointer to the initial character of a null-terminated multibyte strings that represents the name used to invoke the program itself (or an empty string "" if this is not supported by the execution environment). The strings are modifiable, although these modifications do not propagate back to the execution environment: they can be used, for example, with std::strtok. The size of the array pointed to by
argv is at least
argc+1, and the last element,
argv[argc], is guaranteed to be a null pointer.
main function has several special properties:
mainin the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace (since C++17))
mainwithout encountering a return statement, the effect is that of executing return 0;.
 See also
C documentation for main function