30.3.2 Control constructs.
Code shall be written using only the five control constructs illustrated in
Fiqures 5 throuqh 9: SEQUENCE, IF-THEN-ELSE, DO-WHILE, DO-UNTIL, CASE. These
control constructs refer to the control logic within a Unit while it is
executing and do not preclude the calling or passing of processor control to
other Units (e.g., subroutines, procedures, functions, exception handlers,
interrupt service routines).