This program is suppoded to get an input of any number in any number system with a base from 2(binary) to 62, which includes all digits plus all capital and then all lower case letters.

Code:

#include <iostream>
#include <string>
using namespace std;
string relet (int input)
{
string output;
if (input == 0)
output="0";
if (input == 1)
output="1";
// ect, ect, ect.
if (input == 61)
output="z";
return output;
}
int unlet (string input)
{
int output;
if (input == "0")
output=0;
if (input == "1")
output=1;
//ect, ect, ect.
if (input == "z")
output=61;
return output;
}
int main ()
{
string number;
int base;
int newbase;
// (removed for space) This part gets user input for number, base, and newbase.
const int length=number.length();
int input[length];
int * output;
output[0]=0;
// This loop puts the number into array "input", while reversing the numbers
// and replaces letters with their decimal number equivilents
int x=0;
int y=length-1;
string buffer;
start1:
buffer=number[y];
input[x]=unlet (buffer);
x++;
y--;
if (x != length)
goto start1;
y=0;
x=0;
// -THE IMPORTANT PART-
// subtracts 1 from the input
substart:
if (input[x] == 0)
{
input[x]=base-1;
x++;
if (x == length) // end if the input is 0
goto finish;
goto substart;
}
input[x]--;
x=0;
// adds 1 to the output
addstart:
// this adds another digit to the output when nessecary
if (x > y)
{
output = new int;
output[x]=0;
y++;
}
if (output[x] == newbase-1)
{
output[x]=0;
x++;
goto addstart;
}
output[x]++;
x=0;
goto substart;
finish:
//(removed) outputs the "output" array starting from the top down and uses the
//"relet" function.

It works sometimes, but if the output is more than 2 digits it will sometimes add 1 to the second digit, and it crashes if the output is more than 4 digits long.

I have gone through the code countless times and cannot figure out what is making it not work. I can post the full code it anyone wants.