Fixed-point numbers contain p digits. For fixed-point decimal numbers, q of those digits may be fractional digits. Fixed-point binary numbers are always integers (q =0). For example:
DECLARE K FIXED BINARY(15); DECLARE D FIXED DECIMAL(7,2);
In this example, the values of K are fixed-point integers with 15 binary digits. Therefore, K can hold any value in the range -32768 to +32767 or -(2**⊃15) to (2**⊃15)-1. The values of D are fixed-point numbers with seven decimal digits, two of which are fractional digits. Therefore, D can hold any value in the range -99999.99 to +99999.99.
DECLARE U FIXED BINARY(16) UNSIGNED;
The values of U are fixed-point integers with 16 binary digits. Therefore, K can hold any value in the range 0 to 65,535 or 0 to (2** 16)-1.
Because most computers operate most efficiently with binary integers, fixed binary variables should be used whenever possible. The relative efficiency of fixed binary variables used as subscripts, string lengths, DO index variables, and so forth is very significant.
Refer to your Open PL/I User's Guide for a description of the -longint compiler option, which alters the default precision of fixed binary variables from 15 to 31.
Fixed decimal values generally require more bits of storage and are often more computationally complex than values represented in binary, but fixed decimal values are more efficiently converted to and from an external form (for example, at input and output). In certain instances, fixed decimal values may also be less prone to rounding error than their binary counterparts.
An attempt to calculate a fixed decimal value too large to be supported results in a signal of the ERROR condition. An attempt to calculate a fixed binary value too large to be supported will not result in any error and may cause unexpected results. For rules on precision and scale, see the chapter Data Type Conversions.
Operations involving both decimal and binary values always produce a binary result value. However, if the operation must yield a result that has a fractional part, the result is decimal.
If a fixed-point value is converted to a character string or bit string, the length of the string is determined by the declared precision of the fixed-point value p. For a discussion of the conversion rules, see the chapter Data Type Conversions.
Fixed-point values are never rounded unless explicitly rounded by the use of a built-in function. Assignment to a fixed-point variable truncates excess low-order digits. All possible roundings can be performed by using the CEIL, FLOOR, TRUNC, or ROUND built-in functions.
Fixed-point decimal values are always stored as an accurate representation of decimal fractions. A fixed-point decimal value of 10.50 is never represented as 10.49.
Fixed-point constants are written as decimal numbers with or without a decimal point, as shown in the following examples:
5 4.5 4100.01
If a fixed-point constant contains a decimal point, it is considered to be a scaled fixed-point value and is stored and accessed like a fixed decimal variable. Fixed-point constants without a decimal point are integer constants and can be used safely in operations with any other arithmetic value, regardless of that value's base or scale. It is advisable to always write integer constants without a decimal point.
The precision of a fixed-point constant is the number of digits in the constant.