ISeries

Features include a menu-driven interface, multi-user support, terminals and printers (IBM 5250), security, communications and an extensive library-based operating system, OS/400. The big selling point is said to be that applications run and run without modification.

The machine was originally based on a custom IBM CISC CPU, but was later migrated to a PowerPC based RISC CPU family eventually known as RS64. The latest models are based on the POWER4 processor.

The machine survives because the Hardware abstraction layer of its microcode allows the operating system and application programs to take advantage of advances in hardware and software without recompilation. This means that a program written and compiled on a S/38 does runs as a native 64 bit program. The HAL allows a system that costs $9000 to run the exact same operating system and software as a $2 million system

Programming languages available for this machine include RPG, assembly language, C, C++, Java, COBOL, SQL, and REXX. Several CASE tools are available: Synon, AS/SET, Lansa.

Commands in the Command Language (CL) are promptable and most provide cursor sensitive help to make entering parameters easier. A command consist of a three letter verb and a subject part. This makes it easy to understand CL code. Examples:

• CRTUSRPRF - Create user profile
• DLTLIB - Delete lib
• CPYF - Copy file

It was designed as the successor of the IBM System/38 and the IBM System/36. The programmers that worked on OS/400, the operating system of the AS/400, did not have a UNIX background. Mr Frank Soltis, the head architect, says that this is the main difference between this and any other operating system.