There is a load button and a selector switch on the machine, but they do just barely enough to get the process started. The rest in accomplished by a technique sometimes called the “bootstrap technique.” – Buchholz: The System Design of the IBM Type 701 Computer
Division should be the inverse of multiplication. Since multiplying two full-word (35-bit) factors generates a double-length (70-bit) product in the accumulator and /MQ/ register, division has been similarly arranged to start with a double-length (70-bit) dividend stored in the accumulator and /MQ/ register. This appears to be an elementary piece of logic, and it is surprising that a double-length dividend has not been provided in other computers of this type.
Colossus - The Greatest Secret in the History of Computing
Reviving a computer system of 25 years ago - Wirth, 2014
title Rechnen mit Maschinen author W. de Beauclair published Friedr. Vieweg & Sohn, Braunschweig, 1968 url https://ia801704.us.archive.org/14/items/rechnenmitmaschidebe/rechnenmitmaschidebe.pdf
https://www.youtube.com/watch?v=p2LZLYcu_JY