These expressions occur in selection and repetition statements. All other statements are represented by circles. Selection A selection statement selects one of two or more alternative substatements for execution. Note that there is a single entry and a single exit point represented by dots. . A good programming tip is to avoid nesting in the then part of a if-statement.
Loops allow a block of statements to be repeated a number of times.
The index variable is a special variable in the loop that controls the number of repetitions. Note the single entry and exit points. . One hazard with loops is the possibility of infinite looping . The test expression must at some point have a False value in order to ensure the termination of the loop. An index variable within the test-expression is usually initialized, incremented, and tested in order to control when to terminate the loop.