TAL Programmer's Guide

Glossary
096254 Tandem Computers Incorporated Glossary–5
definition structure. A declaration that describes a structure layout and allocates storage
for the structure layout. Contrast with “referral structure” and “template structure.”
dereferencing operator. A period (.) prefixed to an INT simple variable, which causes the
content of the variable to become the standard word address of another data item.
direct addressing. Data access that requires only one memory reference and that is
relative to the base of the global, local, or sublocal area of the user data segment.
directive. See “compiler directive.”
DO statement. A statement that executes a posttest loop until a true condition occurs.
doubleword. A 32-bit storage unit for the INT(32) or REAL data type.
DROP statement. A statement that frees a reserved index register or removes a label
from the symbol table.
D-series system. A system that is running a D-series release version of the operating
system.
entry point. An identifier by which a procedure can be invoked. The primary entry
point is the procedure identifier specified in the procedure declaration. Secondary
entry points are identifiers specified in entry-point declarations.
entry-point declaration. A declaration within a procedure that provides a secondary
entry point by which that procedure can be invoked. The primary entry point is the
procedure identifier specified in the procedure declaration.
environment register. A facility that contains information about the current process, such
as the current RP value and whether traps are enabled.
equivalenced variable. A declaration that associates an alternate identifier and
description with a location in a primary storage area.
expression. A sequence of operands and operators that, when evaluated, produces a
single value.
EXTDECS. A file, provided by the operating system, that contains external declarations
for system procedures. System procedures, for example, manage files, activate and
terminate programs, and monitor the operations of processes.
extended data segment. A segment that provides up to 127.5 megabytes of indirect data
storage. A process can have more than one extended data segment:
The compiler allocates an extended data segment when you declare extended
indirect arrays or indirect structures.
Your process can also allocate explicit extended data segments.
extended indirect addressing. Data access through an extended (32-bit) pointer.
extended pointer. A 32-bit simple pointer or structure pointer. An extended pointer can
contain a 32-bit byte address of any location in virtual memory.