C++ program to convert decimal to hexadecimal

Question

I wrote a program to convert a decimal string to hexadecimal by using a switch command to the letter but if I use char the program does not work well! Without switch I can't deal with the number above 9 .. I hope that u did understand me because my language is not that good.

So this my program

BTW if put it int instead of char it work fine but it's become 11 instead of B

#include <iostream>
using namespace std;
int main()
{
    int n, i, c=0, t;
    char a[50];

    cout << "Enter a decmail number :\n";
    cin >> n;
    t = n;

    for (i = 0; t > 0; i++)
    {
        if (a[i] % 16 > 9)
        {
            switch(a[i])
            {
                case 10 : a[i] = 'A'; break;
                case 11 : a[i] = 'B'; break;
                case 12 : a[i] = 'C'; break;
                case 13 : a[i] = 'D'; break;
                case 14 : a[i] = 'E'; break;
                case 15 : a[i] = 'F'; break;
            }
        }
        else
        {
            a[i] = t % 16;
        }
        t = t / 16;
    }    
    cout << n << " In hexdecmail = ";
    for(c = i - 1; c >= 0; c--)
    {
        cout << a[c];
    }
}

`a[i]=t%16;` ==> `a[i]=t%16 + '0';` to get the ascii value of the digit. — mch, Feb 28 '17 at 16:32
Since you tagged this as C++, you could use `std::hex` manipulator. — Thomas Matthews, Feb 28 '17 at 16:33
This is already answered here -- http://stackoverflow.com/questions/3464194/how-can-i-convert-an-integer-to-a-hexadecimal-string-in-c — Jubin Chheda, Feb 28 '17 at 16:33
If you are programming in the C language, you could use the `%x` format specifier to `printf`. — Thomas Matthews, Feb 28 '17 at 16:34
@JubinChheda that question is asking how to do what OP is trying to do, but that's not what OP is asking here. He is asking about a bug in his code. — François Andrieux, Feb 28 '17 at 16:35
std::cout << std::hex << n; will output it in hex if you are looking for a fast solution. — z32a7ul, Feb 28 '17 at 16:37
@Thomas Matthews im newbie in c++ i don't know what is this ? — asim, Feb 28 '17 at 16:40
@asim: search, research and learn. Search the internet for "c++ print hex example". Search your favorite C++ resource for "std::hex" or "hex". I like to use the index in the back of my books. ;-) — Thomas Matthews, Feb 28 '17 at 16:44

Ajay Brahmakshatriya · Accepted Answer · 2017-02-28T16:49:07.267

The problem here is that 1 is not the same as '1'. 1 is the number one while '1' is a character constant. To convert 1 to '1' you have to add '0' to the number. So you can change the line a[i] = t%16; to a[i] = t%16 + '0';

Also instead of putting the if condition and the switch case on a[i], you need to put it on t%16, because a[i] is not yet set. Rest it should work fine.

Edit : To understand how the conversation from number to character constants work you need to understand how characters are represented internally.

Each character like a-z, A-Z , 0-9 and the special characters are assigned a number between 0 and 256. This numbering is called the ASCII value of the character. You can find the list of all ASCII values here.

The ASCII value of '0' is 48. That of '1' is 49, '2' is 50 and so on. Now what you have is the number (you get by doing t%16). Say it is 3 . To convert to its ASCII code(51) you will have to add 48. Similarly all numbers between 0-9 can be converted to their ASCII values by adding 48. This is because the ASCII values of the digits are continuous.

Often it is difficult to remember the ASCII value 48. So instead you can just write '0' which internally means 48.

I hope this helps.

C++ program to convert decimal to hexadecimal

1 Answers1