I have fond memories of the 1401, although I never programmed one. In the mid 60s I worked for the Harvard Computer Center. We had a 1401 whose sole job was a tape to print server for the 7094. It had attached a 1403 printer, a screaming behemoth (literally) that could print 600 lines per minute. http://www.columbia.edu/cu/computinghistory/1403.html compares the sound of a 1403 to a jet plane, an old jet, mind you, now one of those whisper quite modern ones. There are stories of people writing music to be played on a 1403, maybe even true. Another feature was the 1301 disk drive, the size of two refrigerators, with an astounding 28 megabytes of storage,whirling away at 1800 rpm. For a mere $2000 a month you could have your own.
Shirriff has written several posts about the IBM 1401: his notes on SMS logic cards are particuarly interesting. Sort of like a services architecture, only instead of "real time database" as a component it's "three-way OR". http://www.righto.com/2015/03/a-database-of-sms-cards-techno...
As the first footnote explains, bi-quinary numbers are what an abacus uses: one part is 0,1,2,3 or 4 and the other is 0 or 5. Qui-binary numbers are the opposite: one part is 0,2,4,6 or 8 and the other part is 0 or 1.
Computers tha one person can carry are for wimps.