The Genesis of an Early Stored-Program Computer: CSIRAC

One of the earliest vacuum-tube stored-program computers (CSIRAC) was developed in 1947-1951 under the auspices of the Australian Council for Scientific and Industrial Research. The word length was 20 bits, and storage consisted of about 1000 words in mercury delay lines and about 4000 words on a magnetic disk. Its execution rate approached 1000 instructions per second. The computer was notable for its logical design, which made programming easy and led to economic use of the limited storage. A multiplier was incorporated, and various single-word and single-bit registers were used to assist in relative addressing, subroutine linking, reentrant programming, and decision making. Input was from paper tape and output to paper tape and a modified teletypewriter.