Help with Postfix Calculator

I am getting a segmentation fault 11 where my if and if-else statements begin in the EVALUATE function here. I've only included the MAIN and the EVALUATE functions, as my other areas of the program I believe it be working properly. I am a novice to C and could use some help. Can anyone identify where I'm going wrong here?

Code:

// Evaluate
void evaluate(char expression[]) {
    int counter = 0;
    while (expression[counter]) {
        char temp = expression[counter];
        if(expression[counter]=='+') add(); // if "+" then call addition. isn't advancing past this point.....
        else if(expression[counter]=='-') sub(); // if "-" then call subtraction.
        else if(expression[counter]=='*') mult(); // if "*" then call multiplication.
        else if(expression[counter]=='/') divide(); // if "/" then call division.
        else push(temp - '0'); // otherwise, assume it is number. push to stack.
        counter++;
    }
}

// Main
int main() {
    printf("Enter the expression to be evaluated: ");
    char string[100];
    scanf("%s", string);
    evaluate(string);
    printFinal();
}

the code looks ok. better investigate your other functions to see what they are doing.

Thanks. I solved my segmentation fault problem, and now my numbers are just skewed. I'm about to post the whole thing to see if anyone can help me figure out why. Thanks for the help, though, I may have kept looking in the same spots all day!