Calculator program - adding (c compiler)

I made a program from c compiler so that it can add numbers from the input and tell the answer in the output. e.g. i put '5+5' in the input and in the out put it said '10'
To do this I had to change %c to %d and instead of char put int (for integar). Additionally, there has to be space to store two numbers (iNum1 and iNum2).