Procedure Division (cont.) [ COBOL/HP-UX Language Reference for the Series 700 and 800 ] MPE/iX 5.0 Documentation
COBOL/HP-UX Language Reference for the Series 700 and 800
Procedure Division (cont.)
The MOVE Statement
Function
The MOVE statement transfers data, in accordance with the rules of
editing, to one or more data areas.
General Formats
Format 1
Click here to view figure.
Format 2
Click here to view figure.
Syntax Rules
1. Identifier-1 and literal represent the sending area; identifier-2
represents the receiving area.
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|(OSVS) (VSC2) (MF) |
| |
| |
| |
|2. When Format 1 is specified, all identifiers can be either group |
| or elementary items. The data in the sending area is moved into |
| the data item referenced by each identifier-2 in the order in |
| which it is specified. |
| |
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3. CORR is an abbreviation for CORRESPONDING.
4. When the CORRESPONDING phrase is used, all identifiers must be group
items.
5. An index data item or pointer data item or procedure pointer item,
(VSC2) (MF) cannot appear as an operand of a MOVE statement. (See
the section "The USAGE Clause" earlier in this chapter.)
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|(VSC2) (MF) |
| |
| |
| |
|6. A pointer data item can be part of a group that is referred to in|
| a MOVE CORRESPONDING statement; however, no movement of the |
| pointer data item will take place. |
| |
|7. If either the sending or receiving item is a DBCS (USAGE |
| DISPLAY-1) item, then both must be DBCS items. The figurative |
| constant SPACE can be the DBCS sending item. |
| |
________________________________________________________________________
General Rules
1. If the CORRESPONDING phrase is used, selected items within
identifier-1 are moved to selected items within identifier-2,
according to the rules given in the section "The CORRESPONDING
Phrase" earlier in this chapter. The results are the same as
if the user had referred to each pair of corresponding identifiers
in separate MOVE statements.
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|The process is repeated for each destination group. (VSC2) |
|(OSVS) |
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|(MF) |
| |
| |
| |
|2. If identifier-1 is a numeric function-identifier, then |
| identifier-2 must be either a numeric or numeric-edited |
| item. |
| |
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3. The data designated by the literal or identifier-1 is moved to the
data item referenced by each identifier-2, in the order in which it
is specified. The rules referring to identifier-2 also apply to the
other receiving areas. Any subscripting or indexing associated with
identifier-2, is evaluated immediately before the data is moved to
the respective data item.
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|(ANS85) |
|If identifier-1 is reference modified, subscripted, or is a function- |
|identifier, the reference modifier, subscript, or function-identifier |
|is evaluated only once, immediately before data is moved to the first |
|of the receiving operands. |
| |
|The result of the statement: |
| |
| MOVE a (b) TO b, c (b) |
| |
|is equivalent to: |
| |
| MOVE a (b) TO temp |
| MOVE temp TO b |
| MOVE temp TO c (b) |
| |
|where temp is an intermediate result item provided by your COBOL |
|system. |
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4. Any MOVE in which the sending and receiving items are both
elementary items is an elementary move. Every elementary
item belongs to one of the following categories: numeric,
alphabetic, alphanumeric, numeric edited, alphanumeric edited or
floating-point. (OSVS) (VSC2) (MF) These categories are described
in the PICTURE clause. Numeric literals belong to the category
numeric, and nonnumeric literals belong to the category
alphanumeric. The figurative constant ZERO belongs to the category
numeric when moved to a numeric or numeric-edited item. The
figurative constant ZERO belongs to the category alphanumeric in all
other cases. The figurative constant SPACE belongs to the category
alphabetic. All other figurative constants belong to the category
alphanumeric.
The following rules apply to an elementary move between these
categories:
a. 1) The figurative constant SPACE, or an alphanumeric
edited, or alphabetic data item must not be moved to a
numeric or numeric edited data item.
[REV BEG]
2) A numeric edited data item must not be moved to a
numeric or numeric edited data item.[REV END]
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|This restriction is removed. (ANS85) |
________________________________________________________________________
b. A numeric literal, the figurative constant ZERO, a numeric
data item or a numeric edited data item must not be moved to
an alphabetic data item.
c. A non-integer numeric literal or a non-integer numeric
data item must not be moved to an alphanumeric or
alphanumeric-edited data item.
d. All other elementary moves are legal and are performed
according to the rules given in General Rule 5.
5. Any necessary conversion of data from one form of internal
representation to another takes place during legal elementary moves,
along with any editing specified for ,or de-editing implied by,
(ANS85) the receiving data item:
a. When an alphanumeric edited or alphanumeric item is a
receiving item, alignment and any necessary space filling
takes place as defined in the section "Standard Alignment
Rules" in the chapter COBOL Concepts. If the size of the
sending item is greater than the size of the receiving item,
the excess characters are truncated on the right after the
receiving item is filled. If the sending item is described
as being signed numeric, the operational sign will not be
moved; if the operational sign occupies a separate character
position (see the section "The SIGN Clause" earlier in
this chapter), that character will not be moved and the size
of the sending item will be considered to be one less than
its actual size (in terms of standard data format
characters).
b. When a numeric or numeric edited item is the receiving item,
alignment by decimal point and any necessary zero-filling
takes place as defined in the section "Standard Alignment
Rules" in the chapter COBOL Concepts, except where zeros
are replaced because of editing requirements.
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|(ANS85) |
|[REV BEG] |
| |
|When the sending operand is numeric edited, de-editing is implied to |
|establish the operand's unedited numeric value, which can be signed; |
|then the unedited numeric value is moved to the receiving field. |
|The effect of de-editing depends on the setting of the DE-EDIT |
|directive (see your COBOL System Reference for details).[REV |
|END] |
________________________________________________________________________
When a signed numeric item is the receiving item, the sign of
the sending item is placed in the receiving item. (See the
section "The SIGN Clause" earlier in this chapter.)
Conversion of the representation of the sign takes place as
necessary. If the sending item is unsigned, a positive sign
is generated for the receiving item.
When an unsigned numeric item is the receiving item, the
absolute value of the sending item is moved and no
operational sign is generated for the receiving item.
When a data item described as alphanumeric is the sending
item, data is moved as if the sending item were described as
an unsigned numeric integer.
When the receiving item is numeric and the sending item is
defined as alphanumeric, if the content of the sending item
is not an integer, then results of the move are undefined.
(See the section "Incompatible Data" earlier in this
chapter.)
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|(ANS85) |
|When the numeric data item is the sending item the action of the move |
|will be such that a reverse of the move would cause the same value to |
|appear in the numeric edited field (except for truncation). If he |
|data item contains data which does not conform to the edited picture, |
|zero is moved to the target. |
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c. When a receiving field is described as alphabetic,
justification and any necessary space-filling takes place as
defined in the section "Standard Alignment Rules" in the
chapter COBOL Concepts. If the size of the sending item is
greater than the size of the receiving item, the excess
characters are truncated on the right after the receiving
item is filled.
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|(OSVS) (VSC2) (MF) |
| |
| |
| |
|d. When the receiving field is floating-point, the sending item is |
| converted first to internal floating-point and then moved. When |
| data is moved to or from an external floating-point item, the |
| data is converted first to or from its equivalent internal |
| floating-point value. |
| |
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________________________________________________________________________
|(VSC2) (MF) |
| |
| |
| |
|e. When the receiving field is DBCS the sending item must |
| also be DBCS; no conversion takes place. If the sending |
| and receiving items are not the same size the data item |
| will be either truncated or padded with DBCS spaces on the |
| right. |
| |
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6. Any move that is not an elementary move is treated exactly as if it
were an alphanumeric to alphanumeric elementary move, except that
there is no conversion of data from one form of internal
representation to another. In such a move, the receiving area will
be filled without consideration for the individual elementary or
group items contained within either the sending or receiving area,
except as noted in the General Rules of the OCCURS clause.
7. Table 3-10 summarizes the legality of the various types of MOVE
statements. The general rule reference indicates the rule that
prohibits the move or the behavior of a legal move.
Table 3-10. MOVE Statement Data Categories
Click here to view figure.
The MULTIPLY Statement
Function
The MULTIPLY statement causes numeric data items to be multiplied and
sets the values of data items equal to the results.
General Formats
Format 1
Click here to view figure.
Format 2
Click here to view figure.
Syntax Rules
1. Each identifier must refer to a numeric elementary item, except
that in Format 2 each identifier following the word GIVING must
refer to either an elementary numeric item or an elementary
numeric edited item.
2. Each literal must be a numeric literal.
3. The composite of operands, which is that hypothetical data item
resulting from the superimposition of all receiving data items
aligned on their decimal points, must not contain more than 18
digits.
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|(OSVS) (VSC2) (MF) |
| |
| |
| |
|4. Floating-point data items and literals can be used anywhere a |
| numeric data item or literal can be specified. |
| |
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General Rules
1. See the sections "The ROUNDED Phrase" , "
The ON SIZE ERROR Phraseand NOT ON SIZE ERROR Phrase (ANS85)" ,
"Arithmetic Statements" , "Overlapping Operands" and
"Multiple Results in Arithmetic Statements" in this chapter.
2. When Format 1 is used, the value of identifier-1 or literal-1 is
multiplied by the value of identifier-2. The value of the
multiplier (identifier-2) is replaced by this product; similarly
for each successive occurrence of identifier-2 in the
left-to-right order in which identifier-2 is specified.
3. When Format 2 is used, the value of identifier-1 or literal-1 is
multiplied by identifier-2 or literal-2 and the result is stored
in the data item referenced by each identifier-3.
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|he NEXT SENTENCE Statement |
| |
|(MF) |
| |
|Function |
| |
|The NEXT SENTENCE statement transfers control to the next COBOL |
|sentence, that is, following the next period. It does not transfer |
|control to the logically next COBOL verb as occurs with the CONTINUE |
|verb. |
| |
|General Format |
| |
| NEXT SENTENCE |
| |
|Syntax Rule |
| |
|The NEXT SENTENCE statement can be used anywhere a conditional |
|statement or an imperative-statement can be used. |
| |
|General Rule |
| |
|The NEXT SENTENCE statement redirects the flow of the program to the |
|logically next COBOL verb following the next period. |
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|The NOTE Statement |
| |
|(OSVS) |
| |
|Function |
| |
|The NOTE statement introduces a sentence or paragraph that will be |
|treated as comments. |
| |
|General Format |
| |
| NOTE character-string |
| |
|Syntax Rule |
| |
|The character-string can be any combination of characters from the |
|computer character set. |
| |
|General Rules |
| |
| |
| 1. If a NOTE statement is the first sentence of a paragraph, the |
| entire paragraph is treated as comment. |
| |
| 2. If a NOTE statement appears as other than the first sentence of|
| a paragraph, text up to the next separator period is treated as|
| comment. |
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|The ON Statement |
| |
|(OSVS) |
| |
|Function |
| |
|The ON statement allows selective execution of procedural statements |
|on a periodic basis. |
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General Format
Click here to view figure.
(OSVS)
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|(OSVS) |
| |
|Syntax Rules |
| |
| |
| 1. Identifier-1, identifier-2 and identifier-3 must describe |
| unsigned integer numeric elementary items. |
| |
| 2. Literal-1, literal-2 and literal-3 must be unsigned numeric |
| literals. |
| |
|General Rules |
| |
| |
| 1. Prior to the first execution of each ON statement in |
| the program, a counter, implicitly defined for that ON |
| statement (the implicit-ON- counter), is initialized to be |
| zero. |
| |
| 2. Identifier-1, identifier-2 and identifier-3 should, if |
| specified, contain positive integer values at the time of |
| execution of the ON statement. Varying these values between |
| executions of the ON statement will affect subsequent |
| executions of the ON statements. |
| |
| 3. The implicit ON counter cannot be affected in any way other |
| than by transfer of program execution flow to that ON |
| statement. (The ON counter of a called program can only be |
| reset by the cancelling of that program; execution of the EXIT |
| PROGRAM statement and subsequent CALL of the program without |
| intervening CANCEL has no effect upon the implicit ON counter |
| value.) |
| |
| 4. The following value-list is then evaluated: |
| |
| |
| a. the current value of identifier-1 or literal-1, |
| |
| b. a sequence of values being the results of repeatedly |
| adding the current value of identifier-2 or literal-2 to|
| the current value of identifier-1 or literal-1 |
| until the value of identifier-3 or literal-3 is |
| reached. |
| |
| The implicit-ON-counter is then compared with each of this list|
| of values. If an equality is found, then imperative- |
| statement-1 is executed. If no equality is found, then |
| imperative-statement-2 is executed. |
________________________________________________________________________
The PERFORM Statement
Function
The PERFORM statement is used to transfer control explicitly to one or
more procedures and to return control implicitly whenever execution of
the specified procedure is complete.
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|(ANS85) |
|The PERFORM statement is also used to control execution of one or more|
|imperative statements which are within the scope of that PERFORM |
|statement. |
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General Formats
Format 1
Click here to view figure.
Format 2
Click here to view figure.
Format 3
Click here to view figure.
Format 4
Click here to view figure.
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|(ANS85) |
| |
| |
| 1. If procedure-name-1 is omitted, imperative-statement-1 and the |
| END-PERFORM phrase must be specified; if procedure-name-1 is |
| specified, imperative-statement-1 and the END-PERFORM phrase |
| must not be specified. |
| |
| When an imperative-statement-1 is specified, then the |
| END-PERFORM phrase is optional. (MF) |
| |
| 2. In Format 4, if procedure-name-1 is omitted, the AFTER phrase |
| must not be specified. |
| |
| 3. If neither the TEST BEFORE nor the TEST AFTER phrase is |
| specified, the TEST BEFORE phrase is assumed. |
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4. Each identifier represents a numeric elementary item described in
the Data Division. In Format 2, identifier-1 must be described as a
numeric integer.
5. Each literal represents a numeric literal.
6. The words THROUGH and THRU are equivalent.
7. If an index-name is specified in the VARYING or AFTER phrase, then:
a. The identifier in the associated FROM and BY phrases must
reference an integer data item.
b. The literal in the associated FROM phrase must be a positive
integer.
c. The literal in the associated BY phrase must be a nonzero
integer.
8. If an index-name is specified in the FROM phrase, then:
a. The identifier in the associated VARYING or AFTER phrase must
reference an integer data item.
b. The identifier in the associated BY phrase must reference an
integer data item.
c. The literal in the associated BY phrase must be an integer.
9. Literal in the BY phrase must not be zero.
10. Condition-1, condition-2, ... , can be any conditional expression.
(See the section "Conditional Expressions" earlier in this
chapter.)
11. Where procedure-name-1 and procedure-name-2 are both specified and
either is the name of a procedure in the declaratives portion of the
Procedure Division, both must be procedure-names in the same
declarative section.
12. Two AFTER phrases are permitted in Format 4 of the PERFORM
statement.
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|(ANS85) |
|Six AFTER phrases are permitted in Format 4 of the PERFORM statement. |
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________________________________________________________________________
|This limit is raised to fifteen. (MF) |
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|(OSVS) (VSC2) (MF) |
| |
| |
| |
|13. Floating-point data items and literals can be used anywhere a |
| numeric data item or literal can be specified. They can not be |
| used where an integer is required. |
| |
________________________________________________________________________
General Rules
1. The data items referenced by identifier-4 and identifier-7 must
not have a zero value.
2. If an index-name is specified in the VARYING or AFTER phrase, and
an identifier is specified in the associated FROM phrase, the data
item referenced by the identifier must have a positive value.
3. When procedure-name-1 is specified, the PERFORM statement is
referred to as an out-of-line PERFORM statement;
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|(ANS85) |
|when procedure-name-1 is omitted, the PERFORM statement is referred to|
|as an in-line PERFORM statement. |
________________________________________________________________________
4. The statements contained within the range of procedure-name-1
(through procedure-name-2 if specified) for an out-of-line PERFORM
statement
________________________________________________________________________
|(ANS85) |
|or contained within the PERFORM statement itself for an in-line |
|PERFORM statement |
________________________________________________________________________
are referred to as the specified set of statements.
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|(ANS85) |
| |
| |
| |
|5. The END-PERFORM phrase delimits the scope of the in-line PERFORM |
| statement. (See the section "Explicit and Implicit Scope |
| Terminators" in the chapter COBOL Concepts.) |
| |
|6. An in-line PERFORM statement functions according to the following|
| general rules for an otherwise identical out-of-line PERFORM |
| statement, with the exception that the statements contained |
| within the in-line PERFORM statement are executed in place of the|
| statements contained within the range of procedure-name-1 |
| (through procedure-name-2 if specified). Unless specially |
| qualified by the word in-line or out-of-line, all the general |
| rules which apply to the out-of-line PERFORM statement also apply|
| to the in-line PERFORM statement. |
| |
________________________________________________________________________
7. When the PERFORM statement is executed, control is transferred to
the first statement of the specified set of statements (except as
indicated in General Rules 10b, 10c and 10e). This transfer of
control occurs only once for each execution of a PERFORM statement.
For those cases where a transfer of control to the specified set of
statements does take place, an implicit transfer of control to the
end of the PERFORM statement is established as follows:
a. If procedure-name-1 is a paragraph-name and procedure-name-2
is not specified, the return is after the last statement of
procedure-name-1.
b. If procedure-name-1 is a section-name and procedure-name-2 is
not specified, the return is after the last statement of the
last paragraph in procedure-name-1.
c. If procedure-name-2 is specified and it is a paragraph- name,
the return is after the last statement of the paragraph.
d. If procedure-name-2 is specified and it is a section-name,
the return is after the last statement of the last paragraph
in the section.
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|(ANS85) |
| |
| |
| |
|e. If an in-line PERFORM statement is specified, an execution of the|
| PERFORM statement is completed after the last statement contained|
| within it has been executed. |
| |
________________________________________________________________________
________________________________________________________________________
|(MF) |
| |
| |
| |
|f. An EXIT PERFORM statement can be used to exit an in-line |
| perform before executing all statements within the in-line |
| perform. |
| |
________________________________________________________________________
8. There is no necessary relationship between procedure-name-1 and
procedure-name-2 except that a consecutive sequence of operations is
to be executed beginning at the procedure named procedure-name-1 and
ending with the execution of the procedure named procedure-name-2.
In particular, GO and PERFORM statements can occur between
procedure-name-1 and the end of procedure-name-2. If there are two
or more logical paths to the return point, then procedure-name-2 can
be the name of a paragraph consisting of the EXIT statement, to
which all of these paths must lead.
9. If control passes to the specified set of statements by means other
than a PERFORM statement, control will pass through the last
statement of the set to the next executable statement as if no
PERFORM statement referenced the set.
10. The PERFORM statements operate as follows:
a. Format 1 is the basic PERFORM statement. The specified set
of statements referenced by this type of PERFORM statement is
executed once and then control passes to the end of the
PERFORM statement.
b. Format 2 is the PERFORM ... TIMES. The specified set of
statements is performed the number of times specified by
integer-1 or by the initial value of the data item referenced
by identifier-1 for that execution. If at the time of the
execution of a PERFORM statement, the value of the data item
referenced by identifier-1 is equal to zero or is negative,
control passes to the end of the PERFORM statement.
Following the execution of the specified set of statements
the specified number of times, control is transferred to the
end of the PERFORM statement.
During execution of the PERFORM statement, reference to
identifier-1 cannot alter the number of times the specified
set of statements is to be executed from that which was
indicated by the initial value of the data item referenced by
identifier-1.
c. Format 3 is the PERFORM ... UNTIL. The specified set of
statements is performed until the condition specified by the
UNTIL phrase is true. When the condition is true, control is
transferred to the end of the PERFORM statement. If the
condition is true when the PERFORM statement is entered, and
the TEST BEFORE phrase is specified or implied, (ANS85) no
transfer to procedure-name-1 takes place, and control is
passed to the end of the PERFORM statement.
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|(ANS85) |
|If the TEST AFTER phrase is specified, the PERFORM statement functions|
|as if the TEST BEFORE phrase were specified except that the condition |
|is tested after the specified set of statements has been executed. |
|Any subscripting or reference modification associated with the |
|operands specified in condition-1 is evaluated each time the condition|
|is tested. |
________________________________________________________________________
[REV BEG]
When UNTIL EXIT is specified, the specified set of statements
is performed repeatedly until some statement within the set
causes this repetition to end. In the case of an out-of-line
PERFORM, the only statements that will cause this termination
are statements such as EXIT PROGRAM and STOP RUN. In the case
of an in-line PERFORM, the repetition can also be terminated
by the EXIT PERFORM statement and the GO TO statement.[REV
END]
d. Format 4 is the PERFORM ... VARYING. This variation of the
PERFORM statement is used to augment the values referenced by
one or more identifiers or index-names in an orderly fashion
during the execution of a PERFORM statement. In the following
discussion, every reference to identifier as the object of the
VARYING, AFTER, and FROM (current value) phrases also refers to
index-names.
If index-name-1 is specified, the value of identifier-3,
index-name-2, or literal-1 at the beginning of the execution of
the PERFORM statement must correspond to an occurrence number
of an element in the table associated with index-name-1. If
index-name-3 is specified, the value of identifier-6,
index-name-4, or literal-3 at the beginning of the execution of
the PERFORM statement must correspond to an occurrence number
of an element in the table associated with index-name-3.
Subsequent augmentation, as described below, of index-name-1 or
index-name-3 must not result in the associated index being set
to a value outside the range of the table associated with
index-name-1 or index-name-3; except that, at the completion of
the PERFORM statement, the index associated with index-name-1
can contain a value that is outside the range of the associated
table by one increment or decrement value.
If identifier-2 or identifier-5 is subscripted, the subscripts
are evaluated each time the content of the data item referenced
by the identifier is set or augmented. If identifier-3,
identifier-4, identifier-6, or identifier-7 is subscripted, the
subscripts are evaluated each time the content of the data item
referenced by the identifier is used in a setting or augmenting
operation. Any subscripting or reference modification
associated with the operands specified in condition-1 or
condition-2 is evaluated each time the condition is tested.
Representations of the actions of several types of Format 5
PERFORM statements are given on the following pages.
1. If the TEST BEFORE phrase is specified or implied:
When the data item referenced by one identifier is
varied, the content of the data item referenced by
identifier-2 is set to literal-1 or the current value of
the data item referenced by identifier-3 at the point of
initial execution of the PERFORM statement; then, if the
condition of the UNTIL phrase is false, the specified
set of statements is executed once. The value of the
data item referenced by identifier-2 is augmented by the
specified increment or decrement value (literal-2 or the
value of the data item referenced by identifier-4) and
condition-1 is evaluated again. The cycle continues
until this condition is true, at which point control is
transferred to the end of the PERFORM statement. If
condition-1 is true at the beginning of execution of the
PERFORM statement, control is transferred to the end of
the PERFORM statement.
Click here to view figure.
Figure 3-1. The VARYING Option of a PERFORM Statement with the
TEST BEFORE Phrase Having One Condition
When the data items referenced by two identifiers are
varied, the content of the data item referenced by
identifier-2 is set to literal-1 or the current value of
the data item referenced by identifier-3 and then the
content of the data item referenced by identifier-5 is
set to literal-3 or the current value of the data item
referenced by identifier-6. After the contents of the
data items referenced by the identifiers have been set,
condition-1 is evaluated; if true, control is
transferred to the end of the PERFORM statement; if
false, condition-2 is evaluated. If condition-2 is
false, the specified set of statements is executed once,
then the content of the data item referenced by
identifier-5 is augmented by literal-4 or the content of
the data item referenced by identifier-7 and condition-2
is evaluated again. This cycle of evaluation and
augmentation continues until this condition is true.
When condition-2 is true, the content of the data item
referenced by identifier-2 is augmented by literal-2 or
the content of the data item referenced by identifier-4,
the content of the data item referenced by identifier-5
is set to literal-3 or the current value of the data
item referenced by identifier-6, and condition-1 is
reevaluated. The PERFORM statement is completed if
condition-1 is true; if not, the cycle continues until
condition-1 is true.
Click here to view figure.
Figure 3-2. The VARYING Option of a PERFORM Statement with the
TEST BEFORE Phrase Having Two Conditions
At the termination of the PERFORM statement, the data
item referenced by identifier-5 contains literal-3 or
the current value of the data item referenced by
identifier-6. The data item referenced by identifier-2
contains a value that exceeds the last used setting by
one increment or decrement value, unless condition-1 was
true when the PERFORM statement was entered, in which
case the data item referenced by identifier-2 contains
literal-1 or the current value of the data item
referenced by identifier-3.
________________________________________________________________________
|(ANS85) |
| |
| |
| |
|2. If the TEST AFTER phrase is specified: |
| |
| When the data item referenced by one identifier is varied, the |
| content of the data item referenced by identifier-2 is |
| set to literal-1 or the current value of the data item |
| referenced by identifier-3 at the point of execution of the |
| PERFORM statement; then the specified set of statements |
| is executed once and condition-1 of the UNTIL phrase is |
| tested. If the condition is false, the value of the data item |
| referenced by identifier-2 is augmented by the specified |
| increment or decrement value (literal-2 or the value of the |
| data item referenced by identifier-4) and the specified |
| set of statements is executed again. The cycle continues |
| until condition-1 is tested and found to be true, at which |
| point control is transferred to the end of the PERFORM |
| statement. |
| |
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Click here to view figure.
Figure 3-3. The VARYING Option of a PERFORM Statement with
the TEST AFTER Phrase Having One Condition
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|(ANS85) |
| |
| |
| |
| When the data items referenced by two identifiers are varied, the|
| content of the data item referenced by identifier-2 is set to |
| literal-1 or the current value of the data item referenced by |
| identifier-3; then the current value of the data item referenced |
| by identifier-5 is set to literal-3 or the current value of the |
| data item referenced by identifier-6; and the specified |
| set of statements is then executed. Condition-2 is then |
| evaluated; if false, the content of the data item referenced by |
| identifier-5 is augmented by literal-4 or the content of the data|
| item referenced by identifier-7 and the specified set of |
| statements is again executed. The cycle continues until |
| condition-2 is again evaluated and found to be true, at |
| which time condition-1 is evaluated. If false, the content |
| of the data item referenced by identifier-2 is augmented |
| by literal-2 or the content of data item referenced by |
| identifier-4, the content of the data item referenced by |
| identifier-5 is set to literal-3 or the current value of the data|
| item referenced by identifier-6 and the specified set of |
| statements is again executed. This cycle continues until |
| condition-1 is again evaluated and found to be true, at |
| which time control is transferred to the end of the PERFORM |
| statement. |
| |
| After completion of the PERFORM statement, each data item varied |
| by an AFTER or VARYING phrase contains the same value it |
| contained at the end of the most recent execution of the |
| specified set of statements. See Figure 3-4 . |
| |
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Click here to view figure.
Figure 3-4.
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|(ANS85) |
| |
| |
| |
| During the execution of the specified set of statements |
| associated with the PERFORM statement, any change to the VARYING |
| variable (the data item referenced by identifier-2 and |
| index-name-1), the BY variable (the data item referenced by |
| identifier-4), the AFTER variable (the data item referenced by |
| identifier-5 and index-name-3), or the FROM variable (the data |
| item referenced by identifier-3 and index-name-2) will be taken |
| into consideration and will affect the operation of the PERFORM |
| statement. |
| |
| When the data items referenced by two identifiers are varied, |
| the data item referenced by identifier-5 goes through a |
| complete cycle (FROM, BY, UNTIL) each time the content of |
| the data item referenced by identifier-2 is varied. When |
| the contents of three or more data items referenced by |
| identifiers are varied, the mechanism is the same as for two |
| identifiers except that the data item being varied by each |
| AFTER phrase goes through a complete cycle each time the |
| data item being varied by the preceding AFTER phrase is |
| augmented. |
| |
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11. The range of a PERFORM statement consists logically of all those
statements that are executed as a result of executing the PERFORM
statement through execution of the explicit transfer of control to
the end of the PERFORM statement. The range includes all statements
that are executed as the result of a transfer of control by CALL,
EXIT, GO TO and PERFORM statements in the range of the PERFORM
statement, as well as all statements in declarative procedures that
are executed as a result of the execution of statements in the range
of the PERFORM statement. The statements in the range of a PERFORM
statement need not appear consecutively in the source program.
12. Statements executed as the result of a transfer of control caused by
executing an EXIT PROGRAM statement within the range of a PERFORM
statement are not considered to be part of that range.
13. If the range of a PERFORM statement includes another PERFORM
statement, the sequence of procedures associated with the included
PERFORM should itself either be totally included in, or totally
excluded from, the logical sequence referred to by the first
PERFORM. Thus, an active PERFORM statement, whose execution point
begins within the range of another active PERFORM statement should
not allow control to pass to the exit of the other active PERFORM
statement; furthermore, two or more such active PERFORM statements
should not have a common exit.
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|(MF) |
|These restrictions are not enforced. PERFORM statements can be freely|
|nested, and recursion (a PERFORM statement performing a procedure |
|containing it) is allowed. Only the exit point of the innermost |
|PERFORM statement currently being executed is recognized. These rules|
|can be changed by use of the PERFORM-TYPE directive (see your COBOL |
|System Reference). |
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See the following illustrations for examples of legal PERFORM constructs.
Click here to view figure.
14. A PERFORM statement that appears in a section that is not in an
independent segment can have within its range, in addition to any
declarative sections whose execution is caused within that range,
one of the following:
a. Sections and/or paragraphs wholly contained in one or more
non-independent segments.
b. Sections and/or paragraphs wholly contained in a single
independent segment.
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|These restrictions do not apply. (OSVS) (VSC2) |
________________________________________________________________________
15. A PERFORM statement that appears in an independent segment can have
within its range, in addition to any declarative sections whose
execution is caused within that range, only one of the following:
a. Sections and/or paragraphs wholly contained in one or more
non-independent segments.
b. Sections and/or paragraphs wholly contained in the same
independent segment as that PERFORM statement.
________________________________________________________________________
|These restrictions do not apply. (OSVS) (VSC2) |
________________________________________________________________________
MPE/iX 5.0 Documentation
HP 3000 Manuals