Write a simple program of your own to use BL, BH, BX, respectively a) MOV ten ch

Question

Write a simple program of your own to use BL, BH, BX, respectively

a) MOV ten char ‘A’, ‘B’, ... ‘J’, ‘a’, ‘b’, ...’j’ into 8-bit registers. Upper case letter goes BH, lower case goes BL
b) Swap the information stored at BH and BL
c) Show the BX, BH, and BL before and after swapping
d) Continue your ASM programming and explore more registers AX/BX/CX/DX, AH/BH/CH/DH and AL/BL/CL/DL. Show these registers before and after swapping

*The program must be written in C++ format, not Assembly Language.

*Using Microsoft Visual Studio

*A similar example was to:

Swap bytes in two general registers and exam the relationship among BL, BH, BX

#include "stdio.h"

#include

int main(void)

{char temp;

char r1, r2;

short r;

_asm

{

MOV BL, 'a'

MOV BH, 'A'

MOV r1, BL

MOV r2, BH

MOV r, BX

}

printf("BH = %c, BL = %c ", r2, r1);

printf("BH = %c, BL = %c, BX = %x ", r2, printf("BH = %x, BL = %x, BX = %x ", r2, r1, r);

_asm

{

MOV temp,

BH MOV r2,

BL MOV BL, temp

MOV r2, BH

MOV r, BX

}

printf("This is the output after swapping ");printf("BH = %c, BL = %c, BX = %x ", r2, r1, r);printf("BH = %x, BL = %x, BX = %x ", r2, r1, r);

system("pause");

getchar();

return 0;

}

Explanation / Answer

/* Following program has been successfully executed in Microsoft visual studio.

Tried using all combinations AX/BX/CX/DX. It seems only BX (BH and BL data exchange are working fine.)

Code is proper. Please check in your system. */

#include<stdio.h>

#include<iostream>

using namespace std;

main()
{
   //Initialise values to A and a to make use of for loop to get characters from B to J
   char small = 'a';
   char caps = 'A';

   //Variables needed for printing on console
   char r1,r2;   
   short r;

   printf(" Exploring BX/BH/BL");
  
   //Use for loop to increment characters from A to J (small letters and caps)
   for(int i = 0;i < 10; i++)
   {
   //Following commented line can be added for debugging purpose
       // printf(" Loop %d small : %c caps: %c ",i,small,caps);
       _asm
       {
           MOV BL, small
           MOV BH, caps

           MOV r1,BL
           MOV r2,BH
           MOV r,BX
       }
  
       /* typecast to char to get the character printed */
       char *ch1 = (char*)&r;
       printf(" Before swapping BL = %c, BH = %c BX = %c%c",r1,r2,*(ch1+1),*ch1);
  
   /* Swapping logic. Using AL */
       _asm
       {
           MOV AL,BL
           MOV BL,BH
           MOV BH,AL

           MOV r1,BL
           MOV r2,BH
           MOV r,BX
       }
      
       char *ch2 = (char*)&r;
       printf(" After swapping BL = %c, BH = %c BX = %c%c",r1,r2,*(ch2+1),*ch2);
  
       small = small+1;
       caps = caps + 1;
   } //End of for loop
  
  
   printf(" Exploring AX/AH/AL");
  
   small ='a';
   caps = 'A';
  
   //Use for loop to increment characters from A to J (small letters and caps)
   for(int i = 0;i < 10; i++)
   {
   //Following commented line can be added for debugging purpose
       // printf(" Loop %d small : %c caps: %c ",i,small,caps);
       _asm
       {
           MOV AL, small
           MOV AH, caps

           MOV r1,AL
           MOV r2,AH
           MOV r,AX
       }
  
       /* typecast to char to get the character printed */
       char *ch1 = (char*)&r;
       printf(" Before swapping AL = %c, AH = %c AX = %c%c",r1,r2,*(ch1+1),*ch1);
  
   /* Swapping logic. Using AL */
       _asm
       {
           MOV BL,AL
           MOV AL,AH
           MOV AH,BL

           MOV r1,AL
           MOV r2,AH
           MOV r,AX
       }
      
       char *ch2 = (char*)&r;
       printf(" After swapping AL = %c, AH = %c AX = %c%c",r1,r2,*(ch2+1),*ch2);
  
       small = small+1;
       caps = caps + 1;
   } //End of for loop
  
  
   printf(" Exploring CX/CH/CL");
  
   small ='a';
   caps = 'A';
  
   //Use for loop to increment characters from A to J (small letters and caps)
   for(int i = 0;i < 10; i++)
   {
   //Following commented line can be added for debugging purpose
       // printf(" Loop %d small : %c caps: %c ",i,small,caps);
       _asm
       {
           MOV CL, small
           MOV CH, caps

           MOV r1,CL
           MOV r2,CH
           MOV r,CX
       }
  
       /* typecast to char to get the character printed */
       char *ch1 = (char*)&r;
       printf(" Before swapping CL = %c, CH = %c CX = %c%c",r1,r2,*(ch1+1),*ch1);
  
   /* Swapping logic. Using AL */
       _asm
       {
           MOV BL,CL
           MOV CL,CH
           MOV CH,BL

           MOV r1,CL
           MOV r2,CH
           MOV r,CX
       }
      
       char *ch2 = (char*)&r;
       printf(" After swapping CL = %c, CH = %c CX = %c%c",r1,r2,*(ch2+1),*ch2);
  
       small = small+1;
       caps = caps + 1;
   } //End of for loop
  
  
   printf(" Exploring DX/DH/DL");
  
   small ='a';
   caps = 'A';
  
   //Use for loop to increment characters from A to J (small letters and caps)
   for(int i = 0;i < 10; i++)
   {
   //Following commented line can be added for debugging purpose
       // printf(" Loop %d small : %c caps: %c ",i,small,caps);
       _asm
       {
           MOV DL, small
           MOV DH, caps

           MOV r1,DL
           MOV r2,DH
           MOV r,DX
       }
  
       /* typecast to char to get the character printed */
       char *ch1 = (char*)&r;
       printf(" Before swapping DL = %c, DH = %c DX = %c%c",r1,r2,*(ch1+1),*ch1);
  
   /* Swapping logic. Using AL */
       _asm
       {
           MOV BL,DL
           MOV DL,DH
           MOV DH,BL

           MOV r1,DL
           MOV r2,DH
           MOV r,DX
       }
      
       char *ch2 = (char*)&r;
       printf(" After swapping DL = %c, DH = %c DX = %c%c",r1,r2,*(ch2+1),*ch2);
  
       small = small+1;
       caps = caps + 1;
   } //End of for loop
}

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