IBM System/36
A mid-range computer introduced in 1983, which remained popular in the 1990s because of its low cost and high performance. Prices started in the $20k range for the small 5362 to $100+k for the expanded 5360. In 1994, IBM introduced the Advanced 36 for $9,000.
The largest 5360 had 7MB of RAM and 1432MB of hard disk. The smallest 5362 had 256K of RAM and 30MB of hard disk. The Advanced 36 had 64MB of RAM and 4300MB of hard disk, but design issues limit the amount of storage that can actually be addressed by the operating system; underlying microcode allowed additional RAM to cache disk reads and writes, allowing the Advanced 36 to outperform the S/36 by 600 to 800%.
There was only one operating system for the S/36: SSP (System Support Product). SSP consumed about 7-10MB of hard drive space. 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), the Source Entry Utility (SEU), the largely obselete Work Station Utility (WSU), the Screen Design Aid (SDA) and Operational Control Language (OCL).
Using the IBM S/36 is relatively simple. The operator sits in front of a computer monitor, types on a keyboard, and interacts using a series of on-screen forms. S/36 is command-oriented, like MS-DOS, however, S/36 additionally uses more than 70 menus which allow operators to type the number of an appropriate command or response, and application writers can create their own menus and commands ("procedures.")
Programmers use SEU to create or modify a source program which is then compiled into an object program. SEU uses 50 or so templates to assist the operator with the syntax of different types of sources.
By 1985, an application called Programmer/Operator Productivity was widely available and was probably the most popular (and pirated) S/36 software ever written. POP included a full-screen editor called FSEDIT which could be used in place of SEU, which only allowed single-line editing.
Data File Utility allows the programmer to quickly create a simple, single-record display program to add, update and delete records within a file. Also, simple report programs can be created.
Screen Design Aid allows the programmer to create menus, create and update simple forms which are called "display formats" or "prompt screens", and view existing display formats.
By using Operational Control Language, the programmer can assign files and resources to a particular program and pass run-time information like a processing date, order number, or user name to the compiled program. Programs can acquire up to 8 workstations, or run in the background, but usually they run on only one workstation. The largest program size is 64K.
Whenever a program is called, SSP searches in the named user library and then #LIBRARY. Therefore, a system program can be called from any library and all users have access to it.
S/36 has three types of security: (1) password security, (2) a badge reader option that almost no-one ever bought, and (3) resource security. There are five levels of users access and five levels of resource access. By using password and resource security effectively, the administrator (who was at that time often called a DP Manager or Information Systems Manager) can restrict access to critical and secure applications.
The cheapest, and therefore most popular, language compiler for the S/36 is RPG II, a language based on fixed logic cycles which arose in the days of card readers. Other languages include COBOL, FORTRAN and BASIC. Almost every S/36 shop with in-house design uses RPG.
It's interesting to note that the S/36 allows the operator to change a program while it is being used, which can be very dangerous on live data. The S/38 and the iSeries computer do not allow this.
IBM has not marketed the S/36 or Advanced 36 since 2000. Price/performance of the AS/400 (aka iSeries) and hardware technology of the present-generation PC makes the S/36 a much less attractive offering from a different era in computing.