A typical spot for a semantic bug in most programming languages are the loops. They make path testing difficult due to the significantly increased number of possible paths, and they often contain bugs within the loop condition which are hard to find. A even bigger danger conceals within nested loops . All this justifies to do an extra inspection of a program's loops.

The condition of a loop has to be checked at three different times: when the loop is entered, during its execution, and when the loop is left