IBM System/36
IBM System/36
(computer)The largest 5360 had 7MB of RAM and 1432MB of hard disk.The smallest 5362 had 256K of RAM and 30MB of hard disk. TheAdvanced 36 had 64MB of RAM and 4300MB of hard disk, butdesign issues limit the amount of storage that can actually beaddressed by the operating system; underlying microcodeallowed additional RAM to cache disk reads and writes,allowing the Advanced 36 to outperform the S/36 by 600 to800%.
There was only one operating system for the S/36: SSP (System Support Product). SSP consumed about 7-10MB of hard drivespace. Computer programs on the S/36 reside in "libraries,"and the SSP itself resides in a special system library called#LIBRARY.
Components of SSP include the Data File Utility (DFU), theSource Entry Utility (SEU), the largely obselete Work Station Utility (WSU), the Screen Design Aid (SDA) andOperational Control Language (OCL).
Using the IBM S/36 is relatively simple. The operator sits infront of a computer monitor, types on a keyboard, andinteracts using a series of on-screen forms. S/36 iscommand-oriented, like MS-DOS, however, S/36 additionally usesmore than 70 menus which allow operators to type the number ofan appropriate command or response, and application writerscan create their own menus and commands ("procedures.")
Programmers use SEU to create or modify a source programwhich is then compiled into an object program. SEU uses 50or so templates to assist the operator with the syntax ofdifferent types of sources.
By 1985, an application called Programmer/Operator Productivity was widely available and was probably the mostpopular (and pirated) S/36 software ever written. POPincluded a full-screen editor called FSEDIT which could beused in place of SEU, which only allowed single-line editing.
Data File Utility allows the programmer to quickly create asimple, single-record display program to add, update anddelete records within a file. Also, simple report programscan be created.
Screen Design Aid allows the programmer to create menus,create and update simple forms which are called "displayformats" or "prompt screens", and view existing displayformats.
By using Operational Control Language, the programmer canassign files and resources to a particular program and passrun-time information like a processing date, order number, oruser name to the compiled program. Programs can acquire up to8 workstations, or run in the background, but usually they runon only one workstation. The largest program size is 64K.
Whenever a program is called, SSP searches in the named userlibrary and then #LIBRARY. Therefore, a system program can becalled from any library and all users have access to it.
S/36 has three types of security: (1) password security, (2) abadge reader option that almost no-one ever bought, and (3)resource security. There are five levels of users access andfive levels of resource access. By using password andresource security effectively, the administrator (who was atthat time often called a DP Manager or Information SystemsManager) can restrict access to critical and secureapplications.
The cheapest, and therefore most popular, language compilerfor the S/36 is RPG II, a language based on fixed logiccycles which arose in the days of card readers. Otherlanguages include COBOL, FORTRAN and BASIC. Almostevery S/36 shop with in-house design uses RPG.
It's interesting to note that the S/36 allows the operator tochange a program while it is being used, which can be verydangerous on live data. The S/38 and the iSeries computer donot allow this.
IBM has not marketed the S/36 or Advanced 36 since 2000.Price/performance of the AS/400 (aka iSeries) and hardwaretechnology of the present-generation PC makes the S/36 amuch less attractive offering from a different era incomputing.