Choosing efficient computational data items
When you use a data item mainly for arithmetic or as a
subscript, code USAGE BINARY
on the data description
entry for the item. The operations for manipulating binary data are
faster than those for manipulating decimal data.
About this task
However, if a fixed-point arithmetic statement has intermediate results with a large precision (number of significant digits), the compiler uses decimal arithmetic anyway, after converting the operands to packed-decimal form. For fixed-point arithmetic statements, the compiler normally uses binary arithmetic for simple computations with binary operands if the precision is eight or fewer digits. Above 18 digits, the compiler always uses decimal arithmetic. With a precision of nine to 18 digits, the compiler uses either form.
To produce
the most efficient code for a BINARY
data item, ensure
that it has:
- A sign (an
S
in itsPICTURE
clause) - Eight or fewer digits
For
a data item that is larger than eight digits or is used with DISPLAY
or NATIONAL
data items, use PACKED-DECIMAL
.
To produce the most efficient code for a PACKED-DECIMAL
data
item, ensure that it has:
- A sign (an
S
in itsPICTURE
clause) - An odd number of digits (
9
s in thePICTURE
clause), so that it occupies an exact number of bytes without a half byte left over