pTAL Conversion Guide

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Hardware Indicators

pTAL Conversion Guide—527302-002

20-21

Setting $OVERFLOW

For a pTAL program running as a native process, the native compiler generates code

that tests for overflow after every assignment statement if overflow traps are enabled or

if all of the following conditions are true:

•

Overflow traps are disabled.

•

The root operator—the last operator evaluated—on the right side of an assignment

statement is one of the following:

Negate (unary -), +, -, *, /, '/'

$DBL of an INT, FIXED, REAL, or REAL(64) value

$DBLR of an INT, FIXED, REAL, or REAL(64) value

$FLTR of a REAL(64) value

$FIX of a REAL or REAL(64) value

$FIXD

$FIXI

$FIXL

$FIXR of a REAL or REAL(64) value

$INT of a FIXED, REAL, or REAL(64) value

$INTR of a FIXED, REAL, or REAL(64) value

$FIXEDTOASCII

$SCALE for which

1 <= exponent <= 4

•

The next statement is an IF statement that tests $OVERFLOW.

Testing Hardware Indicators

In TAL, you can test the values of hardware indicators anywhere in your program. The

meaning of a hardware indicator, however, can be difficult to determine because of

side effects and because of characteristics of the instructions that set the indicators.

You can test hardware indicators only after one of the following statements:

•

Assignment statement

•

CALL statement

•

SCAN statement

•

RSCAN statement

You can access hardware indicators in pTAL programs only as follows: Hardware

indicators can appear only in the conditional expression of an IF statement. You

cannot:

•

Test a hardware indicator in the conditional expression of a DO-UNTIL statement

or of a WHILE statement.

•

Reference a hardware indicator in an expression other than in the conditional

expression of an IF statement.