how do i add ASCII values?

my assignment is to write a function that adds the ASCII values of the users input. this is what the function looks like right now...

void hash ( char string[] )
int count ;

for( count = 0 ; string[count] != '\0' ; count++ )
printf( "%c", string[count] ) ;

this is where i am do i get the ASCII value, first of all? i think i know how to add it but i cant get it. right now the characters are data type char... and i need them int right? in order to get them ASCII...

any help will be greatly appreciated