The 1960s

A punched card could hold up to 80 alphanumeric characters or, if left unpunched, it was great for penciling in personal reminders such as your grocery list.

At the beginning of the 1960s, mid-sized IBM customers might have used one of two technologies.

One option was 'unit record' technology. Punched card processing involved transfer of information to punched cards and lots of manual card handling; along with sorting, merging, reporting, and summarization using electromechanical unit record equipment. Many early S/360 systems simply automated these legacy unit record applications. Some of those applications may still be running today.

A large unit record installation - cards flying through a sorter was the public 'image' of DP in those days.

A second option was the IBM 1401 system. The all-transistorized 1401 was the first IBM computer designed for the 'mid-market'. The 1401 was quite successful and 1401 emulation was an important option for many early S/360 customers. Who knows? Some 1401 programs may still be running in 2005.

In 1964 IBM introduced a revolutionary family of computers that offered customers a wide range of compatible processors and common I/O peripherals. By today's standards, the capacity of even the largest S/360 system was feeble. Nevertheless, by the standards of the late 1960s, the S/360 was an extraordinary example of advanced design and technology.

A typical IBM 1401 System with card reader/punch, CPU, printer, and reel-to-reel tape drives.

Fortune magazine famously called the System/360 a US$5 Billion gamble. If one assumes US$1 in 1965 is worth more than US$6 today, that means it might be described as a US$30 Billion gamble (in 2005 US$). It was an extraordinary expression of confidence. The task merely involved concurrently designing a comprehensive, enduring, and extendable architecture; designing and building factories to produce and test state-of-the-art components; designing and building factories to produce and test a family of processors and related I/O products; designing, creating, and testing a new operating system, along with key components and utilities; plus hiring and training a new sales and support organization and doing it all while coordinating activities and resources on a worldwide basis in a time before the easy availability of cheap, high bandwidth communications. I am impressed.

Solid Logic Technology (SLT) - individual circuit components were bonded onto a ceramic substrate

The operating system planned for the System/360 was 'Operating System/360', or OS/360. IBM was apparently too busy in those days to give much thought to creative naming. Later, at some point in the development cycle, IBM realized OS/360 would not fit in the limited memory available on entry models. Since the S/360-30 offered ferrite core memory in the range of 16 to 64 K bytes, an alternative to OS/360 was needed.

A typical IBM System/360 Model 30 with CPU and console, reel-to-reel tape drives, card reader/punch, and disk drives

IBM Endicott developed an alternative operating system designed for smaller members of the S/360 family. The first ‘VSE’ was Disk Operating System/360 (DOS/360). DOS/360 first shipped in 1965. It began with a single partition, but quickly grew to three for basic multiprogramming. Later, BTAM added primitive telecommunications. The belief inside IBM was that DOS/360 would cover the entry level for just a few years, then somehow fade away as users moved up to OS/360.

Reel-to-reel tape drives - spinning tapes were the public 'image' of DP in the early days of computing.

In retrospect it may be difficult to understand that assumption. It must be one of those 'it seemed to make sense at the time' things. Clearly, VSE did not simply fade away. Instead, 40 years later we are celebrating the contributions VSE made in the past, continues to make in the present, and is likely to make in the future of IT. z/VSE is a tribute to DOS/360. Even more importantly, z/VSE is a salute to the thousands of exceptional IBM customers who depend on VSE for robust, cost-effective IT solutions.

In 1965, an imaginary DOS/360 customer might have an S/360-30 system with 32K bytes of main memory, 3-4 IBM 2311 disk drives (each with 7.25 MB capacity per removable disk pack), 4 IBM 2401 reel-to-reel tape drives, a 2540 card read/punch, and a 1403 impact line printer.



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