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String comparison Concepts
4.3 String comparison Concepts
This section focuses on string comparisons, character types, and masked comparisons us-
ing default and non-default type assignments.
4.3.1 String comparisons
String comparisons for logical processing are specified using the CRITERIA and TABLE
commands. These comparisons test for one of the following conditions:
•
Absolute equality—tested for by either a change mode CRITERIA command or by a
constant mode CRITERIA command which references a TABLE command that does
not have a MASK parameter coded.
•
Equality under a mask—tested for when the referenced TABLE command has a MASK
parameter coded.
Comparing strings for equality under a mask means that the user has specified, for
each character position of the input data string, that the test performed is one of the fol-
lowing:
Compare the character in that position for absolute equality.
Ignore the character in that position (consider the character, whatever it is, to compare
as equal).
Compare the character in that position for type, for example, alphabetic, numeric, or
some specially defined type.
4.3.2 Character types
An attribute called type may be associated with any character(s) in a character set. The
possible types are identified by the integers 1 through 7. Any single character in a set, for
example \, will either have a type (type 1, type 2, type 3, and so forth.) or not. If it has no
type, it is referred to as untyped. It is possible for any character to be untyped, have one
type, or have multiple types, for example, be type 2 and type 3.
The defining of types, that is, the associating of type numbers with any group of characters
in a character set, is described in the "Character type assignments—TCODE command"
section of the "Specifying input parameters" chapter.
For every standard character set, there is a set of standard default type assignments which,
for most applications, is sufficient without modification. These assignments define the nu-
meric characters 0-9 to be type 1 characters and the uppercase and lowercase alphabetic
characters A-Z and a-z to be type 2 characters. Use of these default type assignments can
be invoked by the TCODE parameter of the VOLUME command.
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Using Logical Processing
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