"Never" is putting it a bit strong. Suppose you are -- sorry, were -- writing a macro that generates the code. Do you want a macro parameter that specifies a one-byte work area?
BTW, the reason for omitting comments was to allow the reader a slight frisson on figuring out how it actually works. As per the following famous enhanced version: *-4 EQU * CLI *+1,B'11111100' EX R15,*-4 BNE error Best regards, Steve Hobson From: "Steve Hobson" <steve_hob...@uk.ibm.com> Sent: Wednesday, 29 August 2012 12:53 AM >Younger readers may like to know that years ago we would test the low two >bits of R15 for zero like this: > CLI *+1,B'11111100' > EX R15,*-4 > BNE error Never necessary to do that: STC 15,X TM X,3 BNE ... Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU