Dividing Only When It Is Safe

Read two whole numbers with a single scanf call, then decide what to print with one if / else if / else chain that has exactly three branches. If scanf did not convert two values, print "error: expected two numbers". Otherwise, if the divisor is 0, print "error: cannot divide by zero". Otherwise print the quotient and the remainder in the form "84 / 5 is 16 remainder 4". The order of the branches is the exercise. Dividing by zero is undefined behaviour, so the only moment you can do anything about it is before the division runs, and the same goes for computing with a variable scanf never wrote. Watch the negative test case too: the remainder takes the sign of the dividend, so -7 / 2 is -3 remainder -1, exactly as lesson 2 showed. One note on this exercise's exit status. The lesson's version used return 1 to tell the operating system that a run failed, which is what a real program does; here the checker compares only what you print, so keep the single return 0 at the end of main and let the chain choose the message.