How do you convert characters from ASCII to Int w/o using the atoi function?

[Andrea Robinson]

I need to convert data that is input from a file from ASCII chars to Ints, but the catch is no atoi and I can ONLY convert number characters and ignore the others, and the # symbol has to act like a break.
For example: if my file inputs $1,956#%34,9 the output will be
1956
349
So I know I need to subtract 0 from the ASCII car to get the int, but how do I get it to skip the other characters and have the # symbol act as a nwln?
I can't use functions. Just loops. *Sigh*
So confused...
I appreciate any advice.

[Rabbit]

I would use a switch statement to test for the ten digits and the hash symbol with a default that will drop the rest.

[horace1]

you can have a loop checking each character, if it is # terminate the loop, if it is a digit add to current value else ignore, e.g.

loop
   read character
   if (character in range '0' to '9') add to value
until (character is '#')

test the algorithm by reading characters from the keyboard then convert it to process files