Question

URGENT HELP NEEDED

Convert the following C++ program into an x86 assembly language program.
Comment the start of each "code block" that performs one of the listed mathematical calculations.
Comments go to the right of the actual code, all starting on the same column.
.

// Global variables
short a = 5;
short b = 6;
short c = 7;
short d = 8;
short e;
short f;
short g;
short h;

// Code
int main()
{
    ++d;
    --c;
    b = a + 2;
    a = d + 9;
    e = a + b - c - d;
    f = -c;
    g = f + e;
    h = -b - c + a;

    // Move a into the eax register
    // Move b into the ebx register
    // Move c into the ecx register
    // Move d into the edx register
    // Call the DumpRegs function   

    // Move e into the eax register
    // Move f into the ebx register
    // Move g into the ecx register
    // Move h into the edx register
    // Call the DumpRegs function   
   
    --h;
    g = g + 6;
    f = 16;
    e = -g - f;
    d = 5 - e;
    c = -c;
    b = c + e - h;
    a = -b + c - d;
   
    // Move a into the eax register
    // Move b into the ebx register
    // Move c into the ecx register
    // Move d into the edx register
    // Call the DumpRegs function   

    // Move e into the eax register
    // Move f into the ebx register
    // Move g into the ecx register
    // Move h into the edx register
    // Call the DumpRegs function   
   
    // Call the WaitMsg function
}

Answer 1

Given the following global variables

short a = 5;
short b = 6;
short c = 7;
short d = 8;

Since all they were datatype of short , in x86 we can use [EAX] type register to store them.

Let us first declare the variables as above,

main:

MOV A,5; //ASSIGNING INTEGER 5 TO A

MOV B,6;  //ASSIGNING INTEGER 6 TO B

MOV C,7;  //ASSIGNING INTEGER 7 TO C

MOV D,8;  //ASSIGNING INTEGER 8 TO D

INC D; //++D Increments D by 1 i.e,8+1=9

DEC C; //--C Decrements C by 1 i.e, 7-1=6

MOV B,A; // perfoms B=A i.e, B=5

ADD B.2 ; //B=5+2=7

MOV A,D;   // perfoms A=D i.e, A=9

ADD A,9; // A=9+9=18

MOV AX,A;

ADD AX,B; // Register AX Stores A+B i.e,18+2=20

MOV BX,C; //BX=6

ADD BX,D; //Register BX stores C+D i.e,6+9=15

SUB AX,BX; //Performs AX-BX i.e, A+B-(C+D) that will be stored in AX i.e,20-15=5

MOV E,AX; // E=5

MOV AX,0; // Intialising AX=0

SUB AX,C; //Stores the negative value of c i.e, -6

MOV F,AX // F=-C i.e,-6

ADD G,F,E; //Adds E,F and stores the result in G i.e, G=-6+5=-1

MOV AX,B;

ADD AX,C; // Register AX Stores B+C i.e,7+6=13

MOV BX,A;

SUB BX,AX // Performs A-(B+C) since B+C stored in AX i.e,18-13=5

MOV H,BX; //H=5;

Since it was mentioned in the problem statement that move the variables into respective registers,

MOV [EAX],A; // Move a into the eax register

MOV [EBX],B;    // Move b into the ebx register
MOV [ECX],C;    // Move c into the ecx register
MOV [EDX],D;     // Move d into the edx register

Call DumpRegs ; // Usually calls the procedure to Display the current values that are present in the registers.

MOV [EAX],E; // Move a into the eax register

MOV [EBX],F;    // Move b into the ebx register
MOV [ECX],G;    // Move c into the ecx register
MOV [EDX],H;     // Move d into the edx register

Call DumpRegs ; // Usually calls the procedure to Display the current values that are present in the registers.

DEC H; //--H Decrements H by 1 i.e, 5-1=4

ADD G,6; //G=G+6 i.e,-1+6=5

MOV F,16; //F=16

MOV AX,G;

ADD AX,F; // Register AX Stores G+F i.e,5+16=21

MOV BX,0;

SUB BX,AX // Stores negative value of AX i.e,-21

MOV E,BX //E=-21 // e = -g - f;

MOV AX,5;

SUB AX,E; // 5-E i.e,5-(-21)=26

MOV D,AX //D=26; //d = 5 - e =26

MOV AX,0; // Intialising AX=0

SUB AX,C; //Stores the negative value of c i.e, -6

MOV C,AX //  c = -c i.e, C=-6

MOV AX,0;

ADD AX,C,E; //AX=C+E i.e,-6+(-21)=-27

SUB AX,H; //-27-4=-31

MOV B,AX //  b = c + e - h i.e, B=-31

MOV AX,B;

ADD AX,D; // Register AX Stores B+D i.e,-31+26=-5

MOV BX,C;

SUB BX,AX // Performs C-(B+D) since B+D stored in AX i.e,-6-(-5)=-1

MOV A,BX; //A=-1; //a = -b + c - d;

Since it was mentioned in the problem statement that move the variables into respective registers,

MOV [EAX],A; // Move a into the eax register

MOV [EBX],B;    // Move b into the ebx register
MOV [ECX],C;    // Move c into the ecx register
MOV [EDX],D;     // Move d into the edx register

Call DumpRegs ; // Usually calls the procedure to Display the current values that are present in the registers.

MOV [EAX],E; // Move a into the eax register

MOV [EBX],F;    // Move b into the ebx register
MOV [ECX],G;    // Move c into the ecx register
MOV [EDX],H;     // Move d into the edx register

Call DumpRegs ; // Usually calls the procedure to Display the current values that are present in the registers.

Call WaitMsg ; //Displays the message "Press[Enter] to continue" and pauses the program until the user presses the enter key.