ANSI method: printf("\033[2J");
Turbo C and C++: void clrscr(void) in conio.h
MSC and Watcom: void _clearscreen(_GCLEARSCREEN)
in graph.h
MIX Power C: void clrscr(void) in bios.h
ECO C: void clrscr in ??? (not given)
IBM MVS: an assembly language routine
on a public library
#pragma linkage(cls,OS)
void cls(void)