Bryan, I do not represent to be a resource on these machines but have read many books on the history of computing. Most of what I've read about the Mark I was in books with chapters on Howard Aiken or Grace Hopper. I seem to recall that the Charles J. Bashe/Emerson W. Pugh book about early IBM machines, IBM's Early Computers (1985), had some information. My memory sort of distills down to the factoid that the Mark I had almost no ability to branch in a "program" owing to the instructions being read from a rather wide punched tape and thus being sequential. I suspect your friend is looking for more depth, but the bibliographies of these books may put him on the right trail. Jim From: vcf-midatlantic <vcf-midatlantic-bounces@lists.vcfed.org> On Behalf Of W. Bryan Caudle via vcf-midatlantic Sent: Friday, October 9, 2020 12:48 PM To: vcf-midatlantic@lists.vcfed.org Cc: W. Bryan Caudle <bcaudle@ctsi.net> Subject: [vcf-midatlantic] Looking for some knowledgeable with the Harvard Mark I