C++ tutorial: http://www.cplusplus.com/doc/tutorial/

The input/output functions of C, stdio.h

The math functions of C, math.h

1) The X Window system (includes a short tutorial and the Xlib manual) http://tronche.com/gui/x/
2) Basic Graphics Programming With The Xlib Library - by Guy Keren http://www.silverhawk.net/notes/tutorials/x/x2.html

The linux and unix man pages with all the basic terminal commands: http://www.unix.com/man-pages.php?query=&apropos=0&section=1&os=All