Program to Calculate Molar Mass

I need to write a C program to calculate the molar mass when given a chemical formula. For example: C6H13NO2.

I've gotten my code to get the formula into a string and validate it. I've stored the possible atomic masses (C,H,N,O,S) in an array. And I'm using a for loop to process the values in the formula string.

What I can't figure out is how to put the digits in the formula together as an integer value and multiply that value by the atomic mass represented by the preceding letter.

Have you looked into strtol?

Originally Posted by tabstop

Have you looked into strtol?

Yes, I am working with that, but it's giving me errors when I run the program. I'll keep working on it.