I appreciate any help; I'm currently getting a problem with trying to concatenate a single char from a structure to an existing string. Basically, the problem is here:

strcat( res, morse_c[j].letter )

morse_c[j].letter should return an alphabet 'a' or 'b', etc...
I'm trying to concatenate that to a char *res and it returns the error:

'strcat' : cannot convert parameter 2 from 'char' to 'const char...