w1.c       open display and close one;
w2.c       create window and exit
w3.C       write in new window "Hello..." and wait any key
w4.C       draw parabola on the mouse clicks
w5.C       draw something in the new font 
w6.C       print all callable fonts       (?)
w7.C       test on draw  XDrawPoints (draw figure on the mouse click)
w8.C       test for keyboard input; draw buttons with digits; input digit string by keyboard or by mouse press on buttons

gcc -lX11 w8.C