Introduction to AS/400

1) History

Rochester – 1956
1961 – Development Lab
1969 – System/3
Advanced Accounting Machine – RPG II
1970 – AS/400 Conceptually born on January 08
1975 – System/32
1977 – System/34
1978 – System/38 (October 24)
1983 – System/36
Too may “midrange”
1982 to 1985 – Fort Knox
1985 end – Rochester in Trouble
1985 – Silver lake (S/36 code on S/38)
1988 – The AS/400
1990 – The Malcolm Baldrige Award
2000 – Marketing of System/36 stopped by IBM

- AS/400 was first introduced as System/38 in 1978. The hardware and software evolved during the lifetime, but the fundamental architecture did not change. In 1983 S/38 was renamed to S/36. The first AS/400 systems were introduced by IBM on June 20, 1988. Dr. Frank Soltis is the chief architect of AS/400 system.
- The IBM Application System/400 popularly known as AS/400 is a family of mid-range business computing systems that supersedes IBM’s highly successful System/3 X family. Multi-user Operating System – A single computer that can interact with multiple users at the same time.
- OS400 is the operating system for the AS/400.
- In 2000, IBM renamed the AS/400 to iSeries, as part of its e-Server branding initiative. The architecture of the system allows for future implementation of 128-bit processors when they become available. Existing applications can use the new hardware without modification.

2) AS/400 in different business

- The AS/400 can be utilized for different business facets. Some models are designed as systems that provide resources to other computers, also known as a "server" in a network of computers, while others are set up for use with terminals or "display stations".
- IBM has sold over 600,000 AS/400's.
- Used in Distribution warehouses, Hospitals, Banking sectors, Insurance companies, Government offices and even manufacturing companies. Utilizes a green screen interface, a built in database that resembles DB2, and a vast array of software to provide business solutions for today’s business needs.

3) Fundamental Architecture Typical AS/400 Configuration

Technology Independence

An AS/400 program does not speak directly to the hardware. It speaks to the technology independent machine interface (TIMI). Between this interface and the actual hardware, are more than four million lines of operating system software called as System License Internal Code (SLIC). An I-Series Program has no knowledge of the hardware, it remains entirely within SLIC.
- What this means?????
When a processor technology changes IBM can re-write the SLIC components that are aware of these technology changes and preserve integrity of MI.
- Live experience:
When AS/400 processor technology moved from 48 bit CISC (Complex Instruction Set Computer) to a 64 bit RISC (Reduced Instruction Set Computer), customers merely saved their programs from 48 bit m/c and restored it back to a 64 bit machine. Compare it to DEC who migrated their VAX machines from 32 bit to 64 bit RISC. It involved 15-20% re-write of the code.

4) Software Integration

- Includes an extensive library-based operating system
- Capable of supporting multiple instances of AIX, LINUX, LOTUS DOMINO, MICROSOFT - WINDOWS 2000 and WINDOWS SERVER 2003.
- LPAR (Logical Partitioning):
a. Feature introduced from IBM's mainframe computers
b. Facilitates running multiple operating systems simultaneously on one AS/400 unit.
c. A system setup with LPAR can even run different operating systems on different partitions while ensuring that one OS cannot run over the memory or resources of another. Each LPAR is given a portion of system resources (memory, hard disk space, and CPU time) via a system of weights that determines where unused resources are allocated at any given time. The operating systems supported (and commonly used) under the LPAR scheme are OS/400, AIX, Linux and Lotus Domino.

5) Programming Languages Supported

- RPG, Assembly language, C, C++, Pascal, Java, Smalltalk, COBOL, SQL, BASIC, PHP and REXX.
- CASE tools: Synon, AS/SET, LANSA, ProGen Plus

6) Control Language (CL)

- Commands in the Control Language (CL) are promotable using the F4, and most provide cursor-sensitive help using the F1, to make entering parameters easier. A command name consists of a three-letter verb and a subject part, also referred to as a noun. Some command names provide a "modifier" as well. This is intended to make it easy to understand CL code.
a. Examples: CRTUSRPRF - Create (verb) user (modifier) profile (noun)
b. DLTLIB - Delete (verb) library (noun)
c. CPYF - Copy file
d. WRKACTJOB - Work with Active Jobs
e. WRKSYSSTS - Work with System Status

7) Integrated Language Environment

- Traditional AS/400 programming is a "one-stop shop", where a programmer writes computer code, compiles the code, and then executes the code. There is no link step that is found in other environments. - In 1995, IBM re-christened the one-stop shop programming style "OPM" (for Original Programming Model) and introduced a new language paradigm called "ILE" (for Integrated Language Environment). ILE had significant enhancements over OPM, including the ability to create modules (similar to .obj or .lib files), and then bind (link) the modules together into a single executable. The executable could be created as a program or a service program (service programs are similar to .lib or .dll files). - The iSeries fully supports the Java language, including a 64-bit JVM that is implemented below the Operating System layer, closer to the hardware for superior performance. With i5/OS V5R4 there is now a 32-bit JVM that is also supported.