Hexadecimal Addition

[Bil M]

I want to be able to add two hexadecimal numbers . Below is the code. This code is for converting from hexadecimal to decimal, so what I want is that when I enter the second Hexadecimal value, it converts to Decimal and then adds both and then converts back to Hexadecimal and displays the added Hexadecimal value.

 
 
#define _CRT_SECURE_NO_WARNINGS            //For scanf Errors
 
#include<stdio.h>
#include<conio.h>
#include<string.h>
#include <stdlib.h>                        //For Clear Screen Errors
 
 
 void main()
 
{
         int i,a[20];
         unsigned long int h=0,m=1;
         char s[20];
         system("cls");
 
        // printf("Convertion from Hexadecimal to Decimal");
         printf("Enter 1st Hexadecimal number");
         scanf("%s",s);
        // printf("Enter 2nd Hexadecimal number");
        // scanf("%s",q);
        // printf("Decimal Equivalent=");
         printf("Addition is = ");
 
         for(i=0;s[i]!=NULL;i++)
         {
 
          switch(s[i])
           {
            case '0':
             a[i]=0;
             break;
            case '1':
             a[i]=1;
             break;
            case '2':
             a[i]=2;
             break;
            case '3':
             a[i]=3;
             break;
            case '4':
             a[i]=4;
             break;
            case '5':
             a[i]=5;
             break;
            case '6':
             a[i]=6;
             break;
            case '7':
             a[i]=7;
             break;
            case '8':
             a[i]=8;
             break;
            case '9':
             a[i]=9;
             break;
            case 'a':
            case 'A':
             a[i]=10;
             break;
            case 'b':
            case 'B':
             a[i]=11;
             break;
            case 'c':
            case 'C':
             a[i]=12;
             break;
            case 'd':
            case 'D':
             a[i]=13;
             break;
            case 'e':
            case 'E':
             a[i]=14;
             break;
            case 'f':
            case 'F':
             a[i]=15;
             break;
            default:
             printf("Entered number is not Hexadecimal.Printed value is notcorrect.");
             break;
 
           }
         }
         i--;
         for(;i>=0;i--)
         {
          h=h+a[i]*m;
          m=m*16;
         }
 
          printf("%ld ",h);
 
          getch();
 
}
 

[whodgson]

Wonder why you would want to do that?
hexadecimal is just another format. You can work in hex format just as you can work in dec format
if x=2b4 (692) and y=3c7 (967)
x+y=67b (1659)

[Bil M]

This is actually a Hexa-to-deci converting code...so I've come up with the solution to convert two hexa to deci and add them together but im getting answer in decimal form...so how do I convert decimal form to hexadecimal form with the above codes and without adding whole new sets of codes

[donbock]

I see this same kind of confusion over and over again in this forum. Bil M, please don't be upset over this reply; it is prompted more by the many other folks who posed this question than it is by what you wrote.

The experts get confused when you say you want to add hexadecimals, or you want to add decimal numbers, or you want to add some other kind of numbers, because the computer only recognizes one kind of number: binary.

What you want to do is

• Allow the operator to enter a number that is expressed in some format. Either the format is implicit ('my program only accepts hexadecimal') or it is explicit ("0x" prefix means hexadecimal, etc).
• Store the operator's entered number into a string.
• Convert that string to a number.
• Perform some operation on that number.
• Convert the result number into a string representation according to some desired format.
• Print the string representation of the result.

Which of these steps are you having trouble with?

[whodgson]

If you stick with donbock all will be made clear.
Before I go though.... in line 21 your format specifier %s should be %x if you intend to provide a number in hex format. In other words you are providing a string representation of a hex number not a number in hex format.
So if you have:

scanf("%x",x);//if x = Ox2b4
scanf("%x",y);//if y = Ox3c7
printf("%x",x+Y)//prints Ox67b...I think

[donbock]

Do you want to support both positive and negative input values?
Are you required to write your own string-to-number conversion or can you use a standard library function? Take a look at strtol or strtoul.

These are the functions I would use in a C program. There may be some slick magical >> alternative if you're using C++. We'll see what the C++ experts have to say.

I'm not a big fan of scanf. I think it is easier to trap illegal input if you separate input from parsing; but that's more of a personal idiosyncracy than a hard and fast rule.

By the way, the main function always returns an int, never void. You should get in the habit of always writing it that way.

[Bil M]

Thanks donbock ....
My task asks for the conversion of Binary to Hexadecimal then the next step to add two hexadecimal numbers and subtract to hexadecimal numbers...so when I add two hexadecimal numbers...i convert them to decimal form and then add them ...but I am lost in converting the decimal number back to Hexadecimal value..

The values should only be positive....
So what is the other option instead of scanf?...

so for example if I provide E as first value and E as second and add them together. ..the result should show 1C...not 28...

[Bil M]

ive updated the code...in the code if you run it ...it will ask for two hexadecimal values...and the answer will be in decimal form..whereas I want it to be in Hexadecimal form

[Bil M]

 
 
#define _CRT_SECURE_NO_WARNINGS            //For scanf Errors
 
#include<stdio.h>
#include<conio.h>
#include<string.h>
#include <stdlib.h>     
 
int main()
 
{
             int i,a[20];
         unsigned long int h=0,m=1,j=0,k=0;
         char s[20],q[20];
         system("cls");
 
        // printf("Convertion from Hexadecimal to Decimal");
         printf("Enter 1st Hexadecimal number");
         scanf("%s",s);
        printf("Enter 2nd Hexadecimal number");
        scanf("%s",q);
        // printf("Decimal Equivalent=");
         printf("Addition is = ");
 
         for(i=0;s[i]!=NULL;i++)
         {
 
          switch(s[i])
           {
            case '0':
             a[i]=0;
             break;
            case '1':
             a[i]=1;
             break;
            case '2':
             a[i]=2;
             break;
            case '3':
             a[i]=3;
             break;
            case '4':
             a[i]=4;
             break;
            case '5':
             a[i]=5;
             break;
            case '6':
             a[i]=6;
             break;
            case '7':
             a[i]=7;
             break;
            case '8':
             a[i]=8;
             break;
            case '9':
             a[i]=9;
             break;
            case 'a':
            case 'A':
             a[i]=10;
             break;
            case 'b':
            case 'B':
             a[i]=11;
             break;
            case 'c':
            case 'C':
             a[i]=12;
             break;
            case 'd':
            case 'D':
             a[i]=13;
             break;
            case 'e':
            case 'E':
             a[i]=14;
             break;
            case 'f':
            case 'F':
             a[i]=15;
             break;
            default:
             printf("Entered number is not Hexadecimal.Printed value is notcorrect.");
             break;
 
           }
         }
         i--;
         for(;i>=0;i--)
         {
          h=h+a[i]*m;
          m=m*16;
          j=j+a[i]*m;
          k=(h+j)/8.5;
         }
 
          printf("%ld ",k);
        //  printf("%ld ",(h+j));
 
          getch();
 
}
 
 
 
 
 

[donbock]

Line 26. NULL is the null pointer value. You want to loop until you find a null character in the string. The null character is '\0' (sometimes casually referred to as 0). These are different things that just happen to both be equal to zero.

You store the second hexadecimal number string into q, but you construct the number itself (j) from digits in a, which only come from string s, which holds the first hexadecimal number.

I'll say it again, lines 26-98 (except line 97) could be replaced by two calls to strtoul.

Lines 100-101. As whodgson indicated in reply #5, the %ld conversion specifier prints the value of a signed long integer as a decimal number, but the %lx conversion specifier prints the value of an unsigned long integer as a hexadecimal number. (By the way, you should use %lu to print the value of an unsigned long integer as a decimal number.)

[Bil M]

I am a little confused . Can you please correct the code and post it again if its not to much trouble. I will look at the code and understand the explanation you have provided. I would really appreciate it.