z/Architecture
The design of the IBM Z processor, its instructions and how it handles memory, which traces back to the System/360 of 1964.
Also written System/360, ESA/390, S/390, 64-bit mode, instruction set
z/Architecture is the processor design of IBM Z: the set of machine instructions, the registers and the rules for how memory is addressed. It was introduced in 2000 with 64-bit addressing, and each new mainframe generation adds instructions to it.
Its history is the important part. It descends directly from the IBM System/360, announced in 1964, through System/370, ESA/390 and others. Each step kept the earlier instructions working. A program written and compiled for the mainframe decades ago can usually run on a new machine without being recompiled.
That compatibility is one of the main reasons organisations keep their mainframe systems. Very large applications, built over many years, keep working through hardware upgrades, while each upgrade makes them faster.
You will see the architecture's history in places like the 24-bit and 31-bit limits in virtual storage, and in assembler and dump output. Newer compilers can also be told which architecture level to build for, so a program can use instructions that only newer machines have.
Where can I learn this hands-on?
Right here, at ZedBank. You take a junior job at a simulated bank and learn each part of the work by doing it, with Zed beside you. There's nothing to install.
Start at ZedBankRelated
- IBM ZIBM's current family of mainframe hardware, and the brand name you will see on most modern mainframe job adverts.
- MainframeA large, highly reliable computer built to run enormous volumes of transactions and batch work for an entire organisation at once.
- AssemblerThe low-level programming language of the mainframe, where each statement matches a single machine instruction.
- Virtual storageThe memory each address space sees, which z/OS maps onto real memory and disk so that every program appears to have its own large space.
- HexadecimalA way of writing numbers in base 16, used everywhere on the mainframe to show the exact contents of bytes.