MVSFORUMS.com

[rnanavaty]

In my program I have 'DS 0H' is defind without sub-variable of 2 bytes. What it indicate in the assembly?

SPACE 2
PRODPAGE DS 0H
PRODPAG1 CLI PREMSW,C'Y'

[semigeezer]

Align the next instruction or data on a half word boundary. Generally most useful if the ALIGN option is not in effect but rarely a service or instruction will require aligned data. All instructions must be halfword aligned, but that is usually the assembler default. I'll leave it to others go into instruction interpretation hardware or the history of S/360 hardware if they think it is important or interesting.

[Bill Dennis]

Many times it's just a handy method of providing an alternate label for branching or data reference. The zero means allocate no storage, just half word align, as semigeezer said.

The length field allows for something akin to redefine.