Editing IBM 1620 (section)

====Requirements and design====
The competing computers in this market were the [[Librascope LGP-30]] and the [[Bendix&nbsp;G-15]]; both were [[drum memory]] machines. IBM's smallest computer at the time was the popular [[IBM&nbsp;650]], a fixed word length decimal machine that also used drum memory. All three used [[vacuum tube]]s. It was concluded that IBM could offer nothing really new in that area. To compete effectively would require use of technologies that IBM had developed for larger computers, yet the machine would have to be produced at the least possible cost.

To meet this objective, the team set the following requirements:
* Core memory
* Restricted instruction set
** No divide or floating-point instructions, use subroutines in the "general program package"
* Wherever possible replace hardware with existing logical machine functions
** No arithmetic circuits, use tables in core memory
* Least expensive Input/Output possible
** No punch cards, use paper tape
** No printer, use operator's console typewriter