131K, etc. I believe IBM was guilty of this in their S/360 marketing literature. Welcome to the debate over who is responsible for the confusion in the use of binary versus decimal prefixes; it has been going on at Wikipedia since 2001, see: https://en.wikipedia.org/wiki/Binary_prefix and https://en.wikipedia.org/wiki/Timeline_of_binary_prefixes Actually I think IBM was fairly rigorous in using decimal prefixes, K meaning 1,000, with annotation K=1024 when appropriate as in the Amdahl article on S/360 architecture. I doubt if it had anything to do with appearance. More importantly I am pretty sure that into the 1980s (perhaps later) in its product literature, product specs and operating system utilities IBM used decimal digits with no prefixes at all. IMO the mess really started with Apple's Macintosh which reported memory and disk capacity using K in a binary sense without any qualification. I can't prove a negative, but I think no OS prior to the Mac OS used any prefixes at all; they simply displayed or printed a decimal number to however many digits necessary, sometimes without commas. It will be interesting to see what this group recalls If u think about it, mixing decimal digits with binary prefixes makes little sense and probably has caused all sorts of problems and confusions such as the infamous 1.44 MB FD. I've always wondered why the programmer at Apple didn't use decimal prefixes and avoid all this nonsense. After all there isn't a lot of difference in coding between a binary shift followed by a decimal conversion as Apple did it and a decimal conversion followed by a decimal shift. Tom