In Vol. 1 Issue 1, Jan. 1958 of the magazine Communications of the ACM, Dr. Saul Gorn discusses the advantages of the computer architecture of Edvac to that of Eniac.
He states that the Edvac had a three-plus-one address word structure, and that the tendencies of his time period were to use one-address hardware and three-plus-zero address pseudo-codes. He then goes on to say that for the future he imagines using variable instruction-word-length machines.
My questions: What is a three-plus-one address word structure? What is a one-address hardware and three-plus-zero address pseudo code? What do these terms mean exactly? I understand what a word is, but not to an extent that would allow me to understand these terms contextually.
Link to this issue of CACM: here. I believe an ACM membership is required to access the magazine. This question refers to Dr. Saul Gorn's Letter to the Editor.