pTAL Conversion Guide

pTAL Conversion Guide—527302-002
20-1
20 Hardware Indicators
This section compares the use hardware indicators in TAL and pTAL.
The term “hardware indicator” refers to one of three fields in the environment (ENV)
register of TNS architecture:
•
The overflow bit
•
The carry bit
•
The condition code
In TAL and pTAL, you test:
•
Overflow by referring to $OVERFLOW
•
Carry by referring to $CARRY
•
Condition codes by referring to one of the following symbols:
Topics:
•
Managing Overflow Traps on page 20-1
•
Overflow Traps Considerations on page 20-12
•
Setting Hardware Indicators on page 20-14
•
Testing Hardware Indicators on page 20-21
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Testing Condition Codes After Comparing Addresses on page 20-26
•
Using Hardware Indicators Across Procedures on page 20-27
Managing Overflow Traps
TAL programs enable and disable overflow traps by manipulating a bit on TNS
architecture’s environment register. A TAL program determines whether an overflow
occurs by testing a bit in the TNS architecture’s environment register.
pTAL programs manage and test for overflow using code that the native compiler
generates.
Topics:
•
Managing Overflow Traps in TAL on page 20-2
•
Managing Overflow and Traps in pTAL on page 20-3
•
Static T Flag on page 20-4
•
OVERFLOW_TRAPS Directive on page 20-4
< <= ‘<‘ ‘<=’
> >= ‘>’ ‘>=’
= <> ‘=’ ‘<>’