HP 3000 Manuals HP 3000 Manuals
Common Features of Arithmetic Statements
The five arithmetic statements, ADD, SUBTRACT, MULTIPLY, DIVIDE, and
COMPUTE have the following features in common:
1. The data descriptions of operands in an arithmetic statement need
not be the same.
If operands are of mixed types, the compiler generates any data
conversion routines necessary to format the data. Note that this
does increase the size of the code space.
If the operands are already defined as COMPUTATIONAL SYNCHRONIZED,
the compiler does not have to generate conversion routines. This
reduces the object program size and its execution time.
Therefore, to maximize efficiency of arithmetic operations,
remember to define the operands as being COMPUTATIONAL
SYNCHRONIZED or with a usage of COMPUTATIONAL-3.
For more information, see the HP COBOL II/XL Programmer's Guide.
2. The maximum size of each operand is 18 digits. The composite of
operands must not contain more than 18 decimal digits.
The composite of operands is the hypothetical data item resulting
from the superimposition of specified operands in an arithmetic
statement after the operands have been aligned on their decimal
points.
For example, in format 1 of the ADD statement, the composite of
operands is determined by using all of the operands in a given
statement.
Therefore, if A = 1234.567, B = 1.2359, and C = 10340.77, the
composite of operands of the statement ADD A, B TO C is
10340.2359.
This number was arrived at by selecting the operand with the
greatest number of digits to the right of the decimal point (in
this case, 1.2359), and then the operand with the greatest number
of digits to the left of the decimal point (which is 10340.77).
These two operands were then superimposed, with the larger number
to the left or right of the decimal point masking the smaller.
3. Arithmetic statements can have multiple results. For example, the
following ADD statement gives the multiple results, A + B, A + C,
and A + D:
ADD A TO B, C, D.
Such statements behave as though they had been written in the
following way:
a. A statement was first written that performs the specified
arithmetic operation, and stores the results in a temporary
location.
b. A sequence of statements was then written that transfers or
combines the value in the temporary location with each of
the single data items specified as a result in the original
arithmetic statement. This hypothetical sequence of
statements was written to perform the transferring or
combining of the temporary value in the same left-to-right
sequence as the multiple results are listed.
Example
The following example illustrates how a temporary location is used in an
ADD statement:
ADD A, B, C TO C, D, E
The above ADD statement is equivalent to the following ADD statements,
where TEMP is a temporary location that stores the intermediate result:
ADD A,B,C GIVING TEMP
ADD TEMP TO C
ADD TEMP TO D
ADD TEMP TO E
Overlapping Operands and Incompatible Data
When a sending and a receiving data item in an arithmetic statement or an
INSPECT, MOVE, SET, STRING, or UNSTRING statement share a part of their
storage areas, the result of the execution of such a statement is
undefined.
Furthermore, except for a class condition, when the contents of a data
item are referenced in the PROCEDURE DIVISION and the contents of that
data item are not compatible with the class, the sign, or the range of
values specified by its PICTURE clause, the result of such a reference is
undefined.
Variable-Length Receiving Items
In ANSI COBOL'85, when a receiving item is a variable-length data item
and contains the object of the DEPENDING ON phrase, the maximum length
of the item is used.
In ANSI COBOL'74, the length is computed using the object of the
DEPENDING ON phrase.