debian man page for readkey

readkey(3alleg4)						  Allegro manual						  readkey(3alleg4)

NAME
       readkey - Returns the next character from the keyboard buffer. Allegro game programming library.

SYNOPSIS
       #include <allegro.h>

       int readkey();

DESCRIPTION
       Returns	the next character from the keyboard buffer, in ASCII format. If the buffer is empty, it waits until a key is pressed. You can see
       if there are queued keypresses with keypressed().

       The low byte of the return value contains the ASCII code of the key, and the high byte the scancode. The scancode remains the same whatever
       the  state  of  the  shift,  ctrl  and  alt keys, while the ASCII code is affected by shift and ctrl in the normal way (shift changes case,
       ctrl+letter gives the position of that letter in the alphabet, eg. ctrl+A = 1, ctrl+B = 2, etc). Pressing alt+key returns  only	the  scan-
       code, with a zero ASCII code in the low byte. For example:

	  int val;
	  ...
	  val = readkey();
	  if ((val & 0xff) == 'd')     /* by ASCII code */
	     allegro_message("You pressed 'd'
");

	  if ((val >> 8) == KEY_SPACE) /* by scancode */
	     allegro_message("You pressed Space
");

	  if ((val & 0xff) == 3)       /* ctrl+letter */
	     allegro_message("You pressed Control+C
");

	  if (val == (KEY_X << 8))     /* alt+letter */
	     allegro_message("You pressed Alt+X
");

       This function cannot return character values greater than 255. If you need to read Unicode input, use ureadkey() instead.

SEE ALSO
       install_keyboard(3alleg4), ureadkey(3alleg4), keypressed(3alleg4), clear_keybuf(3alleg4), simulate_keypress(3alleg4)

Allegro 							   version 4.4.2						  readkey(3alleg4)