Answer Posted / jp

The trick is to use register variables. I have written a sample code in C. There might be some cosmetic works for indention, plz don't bother ;)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#include <dos.h>
#include <stdio.h>
union REGS ax_regs;

/*
Title : Using Registers To Swap Values

Description : Declaring a single variable and using it to swap two values

Author : Jayapriyan VITTOBANE
Turbo C++ V 3.0
*/

void main()
{
clrscr();
ax_regs.h.ah=2;
ax_regs.h.al=3;
printf("\n\n\n\n\n\t\t\tBefore Swapping");
printf("\n\n\n\t\tFirst Value:%5d",ax_regs.h.ah);
printf("\n\n\n\t\tSecond Value:%5d",ax_regs.h.al);
ax_regs.h.ah=ax_regs.h.ah^ax_regs.h.al;
ax_regs.h.al=ax_regs.h.ah^ax_regs.h.al;
ax_regs.h.ah=ax_regs.h.ah^ax_regs.h.al;
printf("\n\n\n\n\n\n\n\n\n\n\t\t\tAfter Swapping");
printf("\n\n\n\t\tFirst Value:%5d",ax_regs.h.ah);
printf("\n\n\n\t\tSecond Value:%5d",ax_regs.h.al);
getch();
}

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