Editing COBOL (section)

=====Control flow=====
COBOL's [[conditional (computer programming)|conditional statements]] are {{code|IF}} and {{code|EVALUATE}}. {{code|EVALUATE}} is a [[switch statement|switch-like statement]] with the added capability of evaluating multiple values and conditions. This can be used to implement [[decision table]]s. For example, the following might be used to control a [[CNC lathe]]: <!-- a more common appliance would be more suitable. -->

<syntaxhighlight lang="cobolfree">
EVALUATE TRUE ALSO desired-speed ALSO current-speed
    WHEN lid-closed ALSO min-speed THRU max-speed ALSO LESS THAN desired-speed
        PERFORM speed-up-machine
    WHEN lid-closed ALSO min-speed THRU max-speed ALSO GREATER THAN desired-speed
        PERFORM slow-down-machine
    WHEN lid-open ALSO ANY ALSO NOT ZERO
        PERFORM emergency-stop
    WHEN OTHER
        CONTINUE
END-EVALUATE
</syntaxhighlight>

The {{code|PERFORM}} statement is used to define loops which are executed {{em|until}} a condition is true (not {{em|while}} true, which is more common in other languages). It is also used to call procedures or ranges of procedures (see the [[#Procedures|procedures section]] for more details). {{code|CALL}} and {{code|INVOKE}} call subprograms and methods, respectively. The name of the subprogram/method is contained in a string which may be a literal or a data item.{{sfn|ISO/IEC JTC 1/SC 22/WG 4|2014|loc=§§ 14.9.4, 14.9.22}} Parameters can be passed [[call by reference|by reference]], by content (where a copy is passed by reference) or [[call by value|by value]] (but only if a [[function prototype|prototype]] is available).{{sfn|ISO/IEC JTC 1/SC 22/WG 4|2014|loc=§ D.6.5.2.2}}
{{code|CANCEL}} unloads subprograms from memory. {{code|GO TO}} causes the program to jump to a specified procedure.

The {{code|GOBACK}} statement is a [[return statement]] and the {{code|STOP}} statement stops the program. The {{code|EXIT}} statement has six different formats: it can be used as a return statement, a [[break statement]], a [[continue statement]], an end marker or to leave a procedure.{{sfn|ISO/IEC JTC 1/SC 22/WG 4|2014|loc=§ 14.9.13.1}}

[[Exception handling|Exceptions]] are raised by a {{code|RAISE}} statement and caught with a handler, or ''{{dfn|declarative}}'', defined in the {{code|DECLARATIVES}} portion of the procedure division. Declaratives are sections beginning with a {{code|USE}} statement which specify the errors to handle. Exceptions can be names or objects. {{code|RESUME}} is used in a declarative to jump to the statement after the one that raised the exception or to a procedure outside the {{code|DECLARATIVES}}. Unlike other languages, uncaught exceptions may not terminate the program and the program can proceed unaffected.