TAL Reference Manual

Equivalenced Variables
TAL Reference Manual—526371-001
10-4
Usage Consideration
type
is any data type except UNSIGNED. The data type determines how much data the
simple pointer can access at a time (byte, word, doubleword, or quadrupleword).
. (period)
is the standard indirection symbol and denotes a standard (16-bit) pointer.
.EXT
is the extended indirection symbol and denotes an extended (32-bit) pointer.
identifier
is the identifier of a simple pointer to be made equivalent to previous-identifier.
previous-identifier
is the identifier of a previously declared simple variable, array, simple pointer,
structure, structure pointer, or equivalenced variable.
index
is an INT constant that specifies an element offset from previous-identifier, which
must be a direct variable The data type of
previous-identifier dictates the element
size. The location represented by
index must begin on a word boundary.
offset
is an INT constant that specifies a word offset from previous-identifier, which can
be a direct or indirect variable. If
previous-identifier is indirect, the offset is from the
location of the pointer, not from the location of the data pointed to.
Usage Consideration
If the previous variable is a pointer, an indirect array, or an indirect structure, the
previous pointer and the new pointer must both contain either:
•
A standard byte address
•
A standard word address
•
An extended address
Otherwise, the pointers will point to different locations, even if they both contain the
same value. That is, a standard STRING or extended pointer normally points to a byte
address, and a standard pointer of any other data type normally points to a word
address.
For portability to future software platforms, declare equivalenced variables that fit
entirely within the previous variable.