Questions regarding the IBM System/360 computers and their descendants.

The System/360 computer line was introduced in in April 1964, and has been very influential. It was one of the first designs to distinguish between architecture and implementation, making it possible to design a range of software-compatible machines at widely varying price and capability points. Present-day IBM System z mainframe servers still have significant compatibility with S/360 application software.

Commonplace architectural features that were introduced with the S/360 include:

  • 8-bit bytes.
  • 32-bit words.
  • Memory addresses expressed in bytes, rather than words.
  • Microcoding in a commercial system.
  • 9-track magnetic tape.

Features introduced in S/360 that are commonplace in the traditional mainframe world, but did not feature in UNIX or DEC operating systems, and are thus rare in mass-market computing in 2020 include:

  • EBCDIC character encoding, as opposed to ASCII. ASCII became the foundation of Unicode.
  • Channel-based input/output.
  • IBM Floating-point representation, largely replaced by IEEE floating-point.

Several manufacturers built S/360-compatible mainframe computers, which presaged the IBM-PC compatible market of the 1980s that evolved into today's Windows and Linux hardware market.