Jim Elwell wrote "What am I missing here?"" What you are missing is the fact that both punch cards and printers really did use only upper case letters. It was not until the introduction of the IBM System/360, in 1964, that the high-speed impact printers (the 1403 N1 "train" printers) offered lower case -- and, even then, not as the default.
The full 8-bit code set, EBCDIC (extended binary coded decimal interchange code), intended for both internal use and data communication, had lower case letters and a great deal more. 64 code points were used for control codes, with the other 192 being available for printable characters. For data communications prior to the introduction of EBCDIC, there was a variant of binary coded decimal (BCD, used on the IBM 1401 and successors), called BCDIC (binary coded decimal interchange code). Like plain old BCD, it was still a 6-bit code, but included a "shift up" and a "shift down" code to allow a choice of upper or lower case. Obviously, such an approach depended on the sequential processing of the data, as happens in data communication in which the receiver is a serial printing device (e.g., the IBM 2741 -- a communicating version of the Selectric Typewriter). The shift concept wasn't new, in that had been used for decades, in a purely mechanical manifestation, on typewriters. Teletypewriters used letters shift and figures shift, from the start, to expand the scope of their very limited 5-bit code to include all upper case letters, all numerals, punctuation, and a few special characters, such as asterisks, ampersands, etc. As for punch cards and EBCDIC, IBM specified a logically-related combination of holes for every code of the 256 available. They could, indeed, be punched (as computer output). However, although I may have missed it, I don't think there was ever a version of IBM's last keypunch machine (the IBM 129 Keypunch/Verifier) that allowed for using lower case in punch card source documents. I didn't closely follow IBM's Keydisk product line (keyboard input, 8" floppy output [not a metric design]). However, given that its output was in EBCDIC form, I think it provided for lower case keyboard entry. Bill Potts, CMS Roseville, CA http://metric1.org [SI Navigator] >-----Original Message----- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] >Behalf Of Jim Elwell >Sent: Sunday, December 19, 2004 08:33 >To: U.S. Metric Association >Subject: [USMA:31700] RE: prefixes in data storage > > >At 18 12 04, 01:04 PM, Bill Potts wrote: >>First, please note that your message contains some sequences (e.g., ᾯ >>and —, presumably intended to be left and right >typographical quotes respectively -- not supported in text mode) >that badly affect readability. > >Sorry about that -- I used a wordprocessor, but used a generic >"paste" rather than "paste unformatted" as I normally do. > >>The maximum theoretical capacity of an 80-column punch card is >actually 120 >>bytes (12 hole positions per column). However, not too many computers were >>equipped to read cards in binary mode and there was no data entry >equipment >>(e.g., keypunches) that could punch them in that mode (nor would it have >>been practical to do so). In practice, each column contained less >>information than today's byte. Rather, it contained only as much >information >>as a 6-bit character. > >You certainly remember punch cards better than I do, but your >6-bit character does not make sense to me. 2^6 is 64, but the >alphabet (upper & lower case) plus 10 digits is 62 different >characters, not counting punctuation. If memory serves, the cards >DID support both upper and lower case, plus a variety of >punctuation symbols. > >What am I missing here? > >Jim Elwell > > > >Jim Elwell, CAMS >Electrical Engineer >Industrial manufacturing manager >Salt Lake City, Utah, USA >www.qsicorp.com >
