pTAL Conversion Guide

Expressions

pTAL Conversion Guide—527302-002

13-10

Relational Operators and Condition Codes

TAL

A condition code (a 2-bit field in the processor status word)—reflects the value of the

most recently evaluated arithmetic or conditional expression:

pTAL

pTAL simulates this 2-bit field when you use a condition code. You can access this field

only by means of the condition code notation.

If the root operator in the conditional expression of an IF statement is a relational

operator (<, =, >, <=, <>, >=, '<', '=', '>', '<=', '<>', '>='), pTAL sets the condition code

according to the result of the comparison.

Relational operators that test the condition code (for example, IF < THEN...) do not set

the condition code.

For more information, see Section 20, Hardware Indicators.

Group Comparison Expressions

TNS and native processes treat odd-byte addresses that refer to data declared with

.EXT differently. For TNS processes, you use a word address to access word-aligned

data in the user data segment. You use a byte address to access all data in an

extended memory segment. TNS processes ignore the low order bit in an extended

memory byte address when they access word-aligned data; therefore, if you use an

odd-byte address to access a 16-bit, 32-bit, or 64-bit word in an extended memory

segment, the TNS process accesses the 16-bit, 32-bit, or 64-bit word that begins one

byte before the odd-byte address you specify.

For native processes, you access all data using a byte address. A native process does

not ignore the low-order bits of addresses; therefore, when you use an odd-byte

address to access a 16-bit word that you have declared with .EXT, you access the data

beginning at the odd-byte address.

These differences can affect TAL and pTAL programs that use group comparison

expressions, as in the following IF statement:

IF a = b FOR 1 WORDS -> @p THEN... ;

Condition Code Meaning

CCL Condition code less than

CCE Condition code equal

CCG Condition code greater than