Pointers for handling input and output

Robust handling of input to a program often requires a large amount of code: parsing the input if it consists of more than just the values, checking that the input makes sense and reporting errors if it does not. For programs of an ad hoc nature or even more than ad hoc writing all that code may be too much work. So the input will often consist of little more than read statements and then some checks to see if the values make sense: