Thread: Stuck in 90s program. please help

Hey guys,

I am still stuck in 90s program of c language looking for someone's help.

I am trying to develop a terminate and stay resident program(TSR) which can displays "HELLO" in bold whenever I press the 'N' key from keyboard.

This is my code here

Code:

#include<dos.h>
#include<bios.h>
#include<stdio.h>
#include<conio.h>
void interrupt (*old)(void);
void interrupt myname(unsigned int AX);
char far *scr=(char far* ) 0xb8000000;

void main()
{
   clrscr();
   old=getvect(0x09);    //SAVE OLD VECTOR IN 'OLD'
   setvect(0x09,myname);//SET NEW VECTOR
   keep(0,1000);        //USED IN TSR TO KEEP MEMORY WHEN TERMINATED
   getch();

    }

     void interrupt myname (unsigned int AX)
      {
      if(*((char*) &AX) == 0x31)
      {
        (*(scr))=0x7048;    //H
        (*(scr+1))=0x7045;    //E
        (*(scr+2))=0x704C;    //L
        (*(scr+3))=0x704C;    //L
        (*(scr+4))=0x704F;    //O

        }
        else{
        (*old)();}        

      }

Looking forward for help

Regards

Jessica

Originally Posted by Salem

Let's assume for the moment you're running on an actual DOS machine, or a virtual machine running an actual DOS machine, and that you're running an actual 90's era 16-bit DOS 'C' compiler like TurboC.

> void interrupt myname(unsigned int AX);
ISR's don't have parameters.
If you want to inspect registers, then you use whatever magic comes with your compiler. Maybe it's a magic variable like _AX, maybe it's a 'struct regs' of some sort.

> (*old)();
I don't think you need an else here, you should always pass on the interrupt to the next service in the chain.

OK. but which condition should I use in order to intercept the 'N' key from keyboard?