IBM System/36 - Overview of The IBM System/36

Overview of The IBM System/36

The IBM System/36 was a simple and popular small business computer system, first announced on 16 May 1983 and shipped later that year. It had a 17-year product lifespan.

The first model of the System/36 was the 5360. It weighed 700 lb (318 kg), cost (US) $100,000 and up, and is believed to have had processor speeds of about 2 MHz and 8 MHz for its two processors, which in 1983 was faster than the "Personal Computers" on the market. The 5362 weighed only 150 pounds (68 kg) and cost (US) $20,000.

In the 1970s, the US Department of Justice brought an antitrust lawsuit against IBM, claiming it was using unlawful practices to knock out competitors. At this time, IBM had been about to consolidate its entire line (System/370, 4300, System/32, System/34, System/38) into one "family" of computers with the same ISAM database technology, programming languages, and hardware architecture. But after the lawsuit was filed, IBM decided it would have two families: the System/38 line, intended for large companies and representing IBM's future direction, and the System/36 line, intended for small companies who had used the company's legacy System/32/34 computers.

The System/36 used virtually the same RPG II, SDA, OCL, and other technologies that the System/34 used, though it was object-code incompatible. Its original displays (at 24×80) were the most popular, and used the same basic screen size still used on modern computers. A 27×132 display was supported c.1987, but never quite caught on. The S/36 was a small business computer; it had an 8-inch diskette drive, between one and four hard drives in sizes of 30 to 716 MB, and memory from 128K up to 7MB. Tape drives were available as backup devices; the 6157 QIC (quarter-inch cartridge) and the reel-to-reel 8809 both had capacities of roughly 60MB. The Advanced/36 9402 tape drive, c.1994, had a capacity of 2.5GB.

The System/36 used a command-line environment, but it was simpler than the System/34 because of 100 or so menus that simplified the command process. Instead of typing "BLDLIBR MYLIB,100,30" to create a user program library, an operator could use menus to find the description "Create a user library" and fill in a form to accomplish the same goal. RPG II was modified from the System/3 days to allow access to the "WORKSTN file" to allow a punched card-based language to interact with a person sitting at a keyboard and monitor. A WORKSTN file was an output file (it wrote to the monitor) and also an input file (because it accepted the user's keyboard input). Thus it was labeled a combined-primary file or a combined-demand file.

Command keys became RPG indicators KA-KY, and different on-screen forms were recognized by different invisible control characters hidden in the forms themselves. Interestingly, since the user had to display a form on the screen in order to type, RPG II provided a way for a program to write output before accepting input. Many successful programmers moved from using the combined-primary WORKSTN file to using a combined-demand file, which had operation codes to read and write the display. There was even a way to code for multiple WORKSTNs; several people could sign on to the same copy of the same program in memory. The largest program size was 64k.

A company called Amalgamated Software of North America (ASNA) produced a third-party compiler for the System/36 in the late 1980s called 400RPG. Another company called BPS created a third-party pre-processor called RPG II-1/2. Both of these products allowed users to write RPG II programs with RPG III opcodes. ASNA also produced an improved file access algorithm called ACCELER8 and a program-canceling utility called TERMIN8. Other third-party companies produced RPG subroutines that greatly enhanced the abilities of RPG. There were at least 230 commercially-available subroutines.

There were a few holdovers from the days of the System/32 (the "Bionic Desk" of 1975): the KEYBOARD, CONSOLE, and DISPLAY files which provided unformatted access to the monitor and keyboard. (CONSOLE came from the System/3 days). Clever System/36 programmers could use a KEYBOARD file to accept commands from the procedure (the "system input file") meaning that a program could be customized at run time without a recompilation.

// LOAD MYPROG // FILE NAME-INPUT // RUN THIS IS CUSTOM DATA SO IS THIS /* (means end of data)