Using the Assert Macro

int sum(int number)
// Precondition:  number => 1
// Postcondition: return sum from 1 to n terms
{
   assert(number >= 1);
   int total = 0;

   for (;number >= 1; number--)
   {
      total = total + number;
   }
   return total;
}

Answer:
Using the assert() macro to detect a runtime error is a bad idea; assert() is meant to serve as a debugging aid rather than handling runtime errors. The problem is this: when you build your application as a release version, every occurrence of assert() will be automatically removed from the code (thanks to macro magic). Consequently, your condition will never be tested.

Instead of assert(), you can use a simple IF statement, such as the following:

if (number >= 1) 
  exit(-1);