Is "argv[0] = name-of-executable" an accepted standard or just a common convention?

Is "argv[0] = name-of-executable" an accepted standard or just a common convention?

c++ c standards argv

c

Regarding 'main(int argc, char *argv[])' [duplicate]

c argv argc

c

Are char * argv[] arguments in main null terminated?

c argv null-terminated

c

argv[argc] ==?

c argv

c