How to Compare two data Blocks

jacek dis however also correct as it is NOT required to open the correct DB's at the point of "presetting" the address registers(before the"LAR1 P#DBX 0.0" and "LAR2 P#DBX 0.0" commands).

As we are talking about not needed commands, allowme too to proposea runtime optimisation of the logicbased on the following changes:
- Usage of both DB registers and no need to open each DB in each loop(Note: preferably done in an FC, be mindful when doing so in an FB as the DB2 register is used for the IDB).
- Usage of only AR1 (the "P#x.y" offset will be used if the start addresses differ)
Note: I kept the BYTE wise comparison, aWORD or DWORD based comparisonwould of course be even better (less loops to do):

[code]LAR1 P#0.0// Load start address into AR1
OPNDB 1// open first DB via DB register 1
OPN DI 2// open second DB via DB register 2
L 64
LOOP: T #_Loop_counter // Loop counter (TEMP variable type INT)
L DBB [AR1,P#0.0] // use "P#x.y" offset if DB1's start address is higher than DB2's
L DIB [AR1,P#0.0] // use "P#x.y" offset if DB2's start address is higher than DB1's
<>I
JC CONT// leave loop if difference encountered (or do other handling here)
+AR1 P#1.0// bump AR1 by 1 Byte
L #_Loop_counter
LOOP LOOP
JU END

CONT: NOP 0// do whatever needs to be done here if difference encountered

END: NOP 0 [/code]
I hope this helps