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COBOL TUTORIAL
FOR BCA STUDENTS OF M G UNIVERSITY |
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A
condition name is an entity which itself is a condition
and as such can have either a true or false value.
However, a condition name cannot be defined independently.
It must always be associated to a data name called
the conditional variable. The condition name may be
defined in any section of the DATA DIVISION and must
be placed immediately after the entry that defines
the conditional variable. There can be more than one
condition names associated to a conditional variable.
In that case all the condition name entries must follow
the entry defining the conditional variable.
A condition name entry specifies either a single value
or a set of values and/or a range of values for the
conditional variable. The condition name becomes true
whenever the conditional variable assumes any of these
values. Otherwise, the condition name is set to false.
It must be noted that it is not possible to set the
value of a condition name explicitly. The value of
a condition name is always set implicitly depending
on the current value of the conditional variable.
The format of the condition name entry is given below:
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The following rules apply for a condition name:
1. Condition names must be described at level 88.
The level number begins in margin A or any position
after it. The condition name must begin from margin
B or any position after it. There must be at least
one space between the level number and condition name.
2. The normal rules for naming a data item also apply
in the case of a condition name.
3. If the same condition name is used in more than
one place, the condition name must be qualified by
the name of its conditional variable.
4. The name of the conditional variable can be used
as a qualifier for any of its condition names. If
the reference to a conditional variable requiresqualification
or subscripting, the same combination of qualification
or subscripting must also be used for the associated
condition name.
5. The values specified through the VALUE clause in
the condition name entry must not conflict with the
data description of the conditional variable. A literal
in the VALUE clause can either a numeric literal,
non numeric literal or figurative constant.
6. When the THRU/THROUGH phrase is used, literal –
1 must be less than literal – 2 and literal
– 3 must be less than literal- 4.
7. A conditional variable can be an elementary item
or a group item. However, it cannot be another condition
name, or a 66-level item (RENAMES clause) or a group
containing the JUSTIFY clause, or the SYNCHRONIZED
clause or the USAGE clause other than DISPLAY.
Example:
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It may be noted that six condition names have been
defined here. All of them are associated with the
conditional variable MARITAL – STATUS. If at
a point of time, MARITAL STATUS gets the value of
2, then the condition names WIDOWED, ONCEMARRIED and
VALID-STATUS will become true and others will become
false.
The condition names can be used as conditions.
Thus in PROCEDURE DIVISION we may have statements,
such as:
(a) IF SINGLE SUBTRACT 125 FROM DEDUCTIONS.
(b) IF ONCE-MARRIED ADD 32 TO SPECIAL-PAY.
(c) IF NOT VALID–STATUS GO TO ERROR–IN–STATUS.
In (a) SUBTRACT 125 FROM DEDUCTIONS will be executed
if MARITAL-STATUS is equal to zero. Similarly, in
(b) the ADD statement will be executed only when MARITAL–STATUS
is equal to 1, 2 or 3 and in (c) the control goes
to the procedure ERROR-IN–STATUS only when MARITAL-STATUS
has a value other than the 0, 1, 2 or 3. As in (c)
a condition name can be preceded by NOT to indicate
the negation of the condition.
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