#include <dos.h>
#include <time.h>
#include <stdio.h>
#include <bios.h>
#include <conio.h>
#define F10 0x0144 /* F10 key */
#define F1 0x013b /* F1 key */
#define TRUE 1
#define FALSE 0
#define PJN_INTER 0x001C /* Timer interrupt */
#define NO_WAIT 0#define WAIT 1
#define CLEAR_WAIT 2
typedef struct {
unsigned key;
void (*function_ptr) ();
} PJN_KEYS;
static int on_key_flag =FALSE;
extern PJN_KEYS *active_keys; /* Nominates active keys in calling program */
void setup_screens(void);
void output_screen(int i, int j);
void print_message(void);
void help_message(void);
void press_a_key(int row);
extern void on_key(void);
extern void off_key(void);
void check_key(void);
void on_key(void);
void off_key(void);
unsigned GetKey( int fWait);
void (interrupt far * old_handler) ();
extern void (*pjn_next_fn)();
PJN_KEYS *active_keys; /* Pointer to pass active keys to functions in ON */
void (*pjn_next_fn)() = NULL; /* Global function to pass to control loop */
main()
{
int i = 0;
int function;
static PJN_KEYS key_calls[] = { { F10, print_message},
{ F1, help_message},
{ '', NULL}
};
active_keys = key_calls; /* Nominate active keys */
setup_screens ();
on_key();
do
{
output_screen(i, function);
i++;
if (pjn_next_fn ! = NULL)
{
function = 1;
printf("Executing a function %lx", pjn_next_fn);
(*pjn_next_fn) (); /* go to next function if not Null */
}
} while (i < 100);
off_key();
}
/*_________Print message that required key pressed ______*/
void print_message(void)
{ off_key();
printf("System stopped with F10 key");
exit(99);
}
/*________Print help message ________________________*/
void help_message(void)
{
off_key();
printf("Help message - F1");
on_key();
return;
}
/*_____________Paint initial screens _________________*/
void setup_screens(void)
{
printf(" Demo program for keyboard interrupts");
press_a_key(10);
}
/*_________________Wait for a key press _________________*/
/* Note: New handler must be off if this is to work.*/
void press_a_key(int wrow)
{
printf(" Press a key");
GetKey(WAIT);
}
/*__________________Dummy screen output __________________*/
void output_screen(int i, int j)
{
printf("\nThe current value is %d function %d ", i, j);
}
/*****************************************************************/
/* ON KEY function similar to the Basic one */
/* NOTE: When the keys are on, no returns are made to the
input buffer. Therefore if a 'press a key' type
function is required, the keys must be turned off
first
*/
/*______________New timer interrupt handler _________________*/
void interrupt far our_handler()
{
int i;
unsigned m_char;
m_char = GetKey ( NO_WAIT );
for( i = 0; i <= 10; i++)
{
if (m_char == active_keys[i].key)
pjn_next_fn = active_keys[i]. function_ptr;
/* Assign next fn ptr */
if ((active_keys[i].function_ptr) == NULL) return;
}
/* Not required, but nice to have */
_chain_intr(old_handler);
}
/*_________________-Turn on new handler __________________*/
void on_key(void)
{
if(on_key flag) /* Handler already loaded. */
{
off_key();
printf("\nYou cannot load the ON_KEY handler twice.");
printf( "\nProgram aborted.");
exit(99);
}
printf(" Turning on key");
old_handler = _dos_getvect(PJN_INTER);
_disable();
_dos_setvect(PJN_INTER, our_handler);
_enable();
on_key_flag = TRUE;
}
/*_______________-Return old keyboard interrupthandler _______*/
void off_key(void)
{
printf(" Disabling");
_disable();
_dos_setvect (PJN_INTER, old_handler);
_enable();
on_key_flag = FALSE;
pjn_next_fn = NULL;
}
/*_______________-Microsoft get key function _________________*/
/* GetKey - Gets a key from the keyboard. This routine
* distinguishes between ASCII keys and function or control
* keys with differenct shift states. It also accepts
* a flag to return immediately if no key is available.
*
* Params: fWait - Code to indicate how to handle keyboard buffer:
* NO_WAIT Return 0 if nokey in buffer, else return key
* WAIT Return first key if available, else wait for key
* CLEAR_WAIT Thow away any key in buffer and wait for new key
*
* Return: One of the following:
*
* Keytype High Byte Low Byte
* ____________ __________ ________
*
* No key available (onlywith NO_WAIT) 0 0
* ASCII value 0 ASCII code
* Unshifted function or keypad 1 scan code
* Shifted function orkeypad 2 scan code
* CTRL function orkeypad 3 scan code
* ALT function or keypad 4 scan code
*
* Note: getkey cannot return codes forkeys not recognized by
* BIOS int 16, such as the CTRL-UP or the 5 key on the
* numeric keypad>
*/unsigned GetKey( int fWait)
{
unsigned uKey, uShift;
/* If CLEAR_WAIT, drain the keyboard buffer. */
if( fWait == CLEAR_WAIT )
while(_bios_keybrd(_KEYBRD_READY ))
_bios_keybrd( _KEYBRD_READ );
/* If NO-WAIT, return 0 if there is nokey ready. */
if ( !fWait && !_bios_keybrd( _KEYBRD_READY ))
return FALSE;
/* Get key code. */
uKey = _bios_keybrd( _KEYBRD_READ );
/* If lowbyte is not zero, it's an ASCII key. Check scan code to
* see if it's on the numerickeypad. If not, clear high byte and
* return.
*/
if( uKey & 0x00ff )
if( (uKey >> 8) < 69 )
return( uKey & 0x00ff );
/* For function keys and numeric keypad, put scan code inlow byte
* and shift state codes in high byte.
*/
uKey >>= 8;
uShift = _bios_keybrd( _KEYBRD_SHIFTSTATUS ) & 0x000f;
switch( uShift )
{
case 0:
return ( 0x0100 | uKey ); /* None (1) */
case 1:
case 2:
case 3:
return( 0x0200 | uKey ); /* Shift (2) */
case 4:
return( 0x0300 | uKey ); /* Control (3) */
case 8:
return( 0x0400 | uKey ); /* Alt (4) */
}
}
/* End of File */