# include <dos.h>

 int iCounter=0;

 void interrupt (*OldPrinterInterruptFunction)( );
 void interrupt NewPrinterInterruptFunction( );

 void interrupt (*OldTimerInterruptFunction)( );
 void interrupt NewTimerInterruptFunction( );

 int main( )
 {
    OldPrinterInterruptFunction=getvect(0x17);
    setvect(0x17,NewPrinterInterruptFunction);

    OldTimerInterruptFunction=getvect(0x08);
    setvect(0x08,NewTimerInterruptFunction);

    keep(0,(_SS+(_SP/16)-_psp));

    return 0;
 }

 /*************************************************************************///------------------  NewPrinterInterruptFunction( )  -------------------///*************************************************************************/void interrupt NewPrinterInterruptFunction( )
 {
    if(_AH==0x00)
    {
       if(_AL>='a' && _AL<='z')
      _AL-=32;

       elseif(_AL>='A' && _AL<='Z')
      _AL+=32;
    }

    (*OldPrinterInterruptFunction)( );
 }

 /*************************************************************************///--------------------  NewTimerInterruptFunction( )  -------------------///*************************************************************************/void interrupt NewTimerInterruptFunction( )
 {
    iCounter++;

    if(iCounter==182)
       setvect(0x17,OldPrinterInterruptFunction);

    elseif(iCounter==364)
    {
       setvect(0x17,NewPrinterInterruptFunction);

       iCounter=0;
    }

    (*OldTimerInterruptFunction)( );
 }