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COBOL TUTORIAL
FOR BCA STUDENTS OF M G UNIVERSITY |
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The picture clause describes the general characteristics
of an elementary data item. These characteristics
are described below:
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In COBOL a data item may be one of the three classes
- numeric, alphabetic
or alphanumeric. The numeric items
consist only of digits 0 to 9. Alphabetic items consist
only of the letters A to Z (a to z) and the space
(blank) character. The alphanumeric items may consist
of digits, alphabets as well as special characters.
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A numeric data item can be signed or unsigned. If
a numeric data is considered as unsigned then during
execution such unsigned data items are treated as
positive quantities. To describe a signed data item
one should use the code character S at the leftmost
end of the picture clause of the corresponding variable.
It is important to note that internally, the operational
sign (S) is not stored as a separate character. The
operational sign is stored at the zone bits of the
rightmost digit position of the data item. While preparing
data for such an input-signed item, care should be
taken to ensure that the data appears on the input
medium in the same form.
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The position of the decimal point is another characteristic
that can be specified in the case of numeric data
items. If the said position is not specified, the
item is considered to be an integer which means that
the decimal point is positioned immediately after
the rightmost digit. It may be noted that in COBOL
the decimal point is not explicitly included in the
data.
The position of the decimal point is merely
an assumed position.
The compiler at the time of compilation only makes
a note of this assumed decimal point. It generates
the object code in such a way that the data items
before taking part in the operations are aligned according
to their assumed decimal points.
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The number of characters or digits required to store
the data item in the memory in known as Size of the
data item.
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All the four general characteristics described above
can be specified through a PICTURE clause. The PICTURE
clause is to be followed by a picture character string
as shown below:
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The
character string can consist of 1 to 30 code characters
that define the above mentioned attributes of the
elementary item. The code characters and their meaning
are given below:
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There is no special code to indicate the size. The
total number of occurrence of 9, X or A in the picture
string indicates the size. The occurrence of V,
P and S are not counted in determining the size
of an item.
The allowable combinations are governed by the following
rules:
In the case of an alphabetic
item the picture may contain only the symbol A.
In the case of a numeric item the picture may contain
only the symbols 9, V, P and S. These are called
operational characters. It must contain at least
one 9. The symbols V and S can appear only once
and S, if it is included, must be the leftmost character
of the picture string. The symbol P can be repeated
on the right or on left (but not on the left of
S) as many times as is required to indicate the
position of the assumed decimal point.
In the case of an alphanumeric item, the picture
may contain all Xs or a combination of 9, A and
X (except all 9 or all A). In the latter case the
item is considered as if the string consists of
all Xs.
The picture clause is only to be specified
for elementary items; it cannot be used for a group
item. The size of a group item is equal to the total
of the sizes of all subordinate elementary items.
The class of a group item is alphanumeric.
The following examples illustrate the PICTURE specification.
Example 1:
PICTURE IS S999V99
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represents a signed data item with a size of 5 characters
and the positions of the assumed point is before
2 places from the rightmost end. Note that S and
V are not counted.
Example 2:
PIC IS PPP9999
- means that the numeric data is of 4 characters
in size and there are 7 positions after the assumed
decimal point. Thus if the data in the memory is
123, the value will be taken as .0000123. If, on
the other hand, the picture were defined as 999PP,
the value would have been 12300.
Example 3:
PIC XXXXXX
- represents the alphanumeric item with size of
6 characters.
Instead of repeating 9, X, A or P in the picture
string, it is possible to write the number of occurrences
of a character enclosed within parenthesis immediately
after the said character.
Thus S9(3)V9(2) is equivalent to S999V99.
X(7) is equivalent to XXXXXX.
P(4)9(3) is equivalent to PPPP999.
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The value clause defines the initial value of the
data item. Generally initialization will be done just
before the first statement in the procedure division
is executed.
The syntax is
VALUE
is literal
The literal can be any numeric value, a nonnumeric
string of characters included within
quote(“) or any figurative constant.
Examples :
01 a pic value is 100
01 compname pic x(15) value is “ABC Company”
01 n pic 9(2) value is ZERO
01 ans pic x value is space
01 result pic x(4) value spaces.
For Group Data value specification
01 test-entry value is “123456”.
02 t1 pic 9(2).
02 t2 pic 9(2).
02 t3 pic 9(2).
Here t1=12,t2=34 and t3=56.
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