Mainframe generally refers to the z/Architecture family of IBM computers which traces its ancestry back to the System 360 introduced by IBM in 1965. The most recent z/Architecture model is the z14 introduced in the summer of 2017. The operating system used by these machines can be z/OS, z/VM, z/VSE, z/Linux, and z/TPF.

Mainframe generally refers to the z/Architecture family of IBM computers which traces its ancestry back to the System/360 introduced by IBM in 1965. The most recent z/Architecture model is the z14 introduced in the summer of 2017. The operating system used by these machines can be z/OS, z/VM, z/VSE, z/Linux, and z/TPF.

Generally speaking, one does not write a "mainframe" application, but instead writes an application that runs in one of the mainframe subsystems: CICS, DB2, IMS, ISPF, TSO, Unix System Services, etc. Each of these subsystems has its own strengths and weaknesses and provides an API.

The primary "claims to fame" for mainframes include

  • IBM's statement of system integrity.
  • the "future-proofing" of applications, where programs written decades previous continue to run on new hardware, new releases and version of the subsystems, and new releases and versions of the operating system.
  • Throughput and performance under load, mainframes are generally running at upwards of 90% capacity while providing subsecond response times.
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