Double word boundary?

[cobollearn]

Hi,

What is Double-word-boundary in COBOL? What does it signify? Are there other such "boundaries"?

[Robert Sample]

From the first days of the 360 machine, back in 1964, memory has been divided into 4-byte chunks called words. Bytes 0 to 3 represent the first word, bytes 4 through 7 represent the second word, and so forth. A double-word boundary is byte 0, 8, 16, .... and certain Assembler instructions need data aligned on double-word boundaries. There are now quad-word boundaries (0, 16, 32, ...) with the advent of 64-bit addressing, but they're not much used (yet).

[cobollearn]

Thanks Robert.

What does it mean that "data aligned on double-word boundaries"?

[nicc]

It means that the data element starts on a double-word boundary which Robert has described above - basically an address that is evenly divisible by 8 or is 0 (hence the 0, 8, 16 etc in robert's post)

[cobollearn]

Ok. Thanks, hopefully I'll start understing these things more as I progress.