Question

So I have this code here, that (for now) just turns a base1 number in to a base 10 number

/**
 * This function is supposed to convert 'number' from base1 to a number in base2.
 * It isn't fully implemented yet, and I've only converted base1 to a base 10 number.
 */
void base1_base2(int base1, int base2, int number) {

    int num, place = 0;
    int rem = number;
    int i;
    for (i = 0; i < num_digits(number); i++) {

        int mod = rem % 10;
        rem = floor(rem / 10);

        int powerResult = pow(base1, place++);
        num = num + mod * powerResult;  
    }

    int base10_num = num;

    printf("The number %i(base%i) in base 10 is: %i\n", number, base1, base10_num);
}

And this calculates the correct base10 number, i.e. the function call
base1_convert(2, 5, 100) would return 4, as expected:

The number 100(base2) in base 10 is: 4

The problem arises when I add this code directly beneath the last printf in that function:

int base2_num = 0;
printf("The number %i(base%i) is: %d\n", number, base1, base2_num);

If the above code is added, it completely changes the result of the first printf, making it return:

The number 100(base2) in base 10 is: 4196784.
The number 100(base2) is: 0

I can not for the life of me figure out why this is happening. I’m guessing it has to do with some pointers, but I haven’t really used any, and I have no idea why adding a seemingly independent variable int base2_num = 0; would change all of that.

Here is the complete modified code after the above lines are added.

void base1_base2(int base1, int base2, int number) {

    int num, place = 0;
    int rem = number;
    int i;
    for (i = 0; i < num_digits(number); i++) {

        int mod = rem % 10;
        rem = floor(rem / 10);

        int powerResult = pow(base1, place++);
        num = num + mod * powerResult;  
    }

    int base10_num = num;

    printf("The number %i(base%i) in base 10 is: %i\n", number, base1, base10_num);

    int base2_num = 0;
    printf("The number %i(base%i) is: %d\n", number, base1, base2_num);

    return;
} 

Edit: And here is the only other function I used, num_digits. It returns the number of digits in an integer.

int num_digits(int integer) {

    char int_string[100];
    int str_length;
    sprintf(int_string, "%i", integer);
    str_length = strlen(int_string);

    return str_length;
}

And here is where I call the function:

int main() {
    printf("Hello World\n");
    base1_base2(2, 5, 100);

    return 0;
}

Answer 1

Just care to write :

int num = 0, place = 0;

And you will be surely done.

That’s why I recommend declaring one variable by line.