Editing Control flow (section)

=== Conditions ===
The earliest [[Fortran]] compilers had statements for testing exceptional conditions.  These included the <code>IF ACCUMULATOR OVERFLOW</code>, <code>IF QUOTIENT OVERFLOW</code>, and <code>IF DIVIDE CHECK</code> statements.  In the interest of machine independence, they were not included in FORTRAN IV and the Fortran 66 Standard.  However since Fortran 2003 it is possible to test for numerical issues via calls to functions in the <code>IEEE_EXCEPTIONS</code> module.

[[PL/I]] has some 22 standard conditions (e.g., ZERODIVIDE SUBSCRIPTRANGE ENDFILE) which can be raised and which can be intercepted by: ON ''condition'' action; Programmers can also define and use their own named conditions.

Like the ''unstructured if'', only one statement can be specified so in many cases a GOTO is needed to decide where flow of control should resume.

Unfortunately, some implementations had a substantial overhead in both space and time (especially SUBSCRIPTRANGE), so many programmers tried to avoid using conditions.

Common Syntax examples:

  '''ON''' ''condition'' '''GOTO''' ''label''