Values for TRUE and FALSE to get away from the standard C syntax of just testing for zero / not zero.
Prototype so we don't need to worry about forward references.
done = loop control in main.
r = denominator(on the right hand side of the operators).
l = numerator (on the left hand side of the operators).
Function Definitions init - set global variables.
input_message = prompt for a command.
input = read command.
get_integer = read an integer.
retrieve_keypress = look for a keypress.
validate = make sure the command is one the program can handle.
execute_command = map the command on to the routines to implement it.
output_divide = implement divide '/'.
output_modulus = implement modulus '%'.
output_values = print out l and r.