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Happy 60th birthday, IBM System/360

Sixty years ago, I was a junior at Temple University in Philadelphia. I was interested in computers, but Temple did not offer any courses in electronic data processing. In fact, in Philadelphia, only the University of Pennsylvania’s Moore School of Engineering offered courses in computers focused primarily on the design of the computers themselves. There, a team of engineers and technicians worked on the development of ENIAC (Electronic Numerical Integrator and Computer), one of the world’s earliest general-purpose electronic digital computers. The project was initially funded by the United States Army, which was interested in the potential of electronic computers to calculate the trajectory of artillery shells.

Fast forward to 1959 when IBM introduced the 1401 mid-range business computer, a versatile and affordable computer that could handle a wide range of data processing. It offered a core memory of up to 16,000 characters – yes, that’s right, 16K. It quickly became one of IBM’s most successful computer systems – the Model T of the computer industry.

In 1964, Temple had two computers, an IBM 1620, marketed as an inexpensive scientific computer – only about 2,000 were built – and an IBM 1401. Although there were no computer courses, there were non-credit evening programming classes for adult learners mostly looking for a career change. They were taught by an IBM Systems Engineer who worked with IBM customers to develop and implement their data processing applications.

I signed up for the classes and was hooked. My first program, written in Autocoder, one level up from machine instructions, making it easier for programmers to write and understand code compared to writing directly in machine language. I still remember my first program: read a deck of punched cards containing alphanumeric information, print each card, add the numbers together, and print the total.

In the 1960s, IBM introduced the 7000 series of mainframe computers with different models designed for various purposes such as scientific computing, business applications, and general-purpose computing. It marked a significant advancement in computer technology, contributing to the evolution of computing capabilities for both commercial and scientific purposes. By then, IBM was selling or leasing five successful but entirely separate computer lines, which made it increasingly difficult to maintain and update them. “IBM in a sense was collapsing under the weight of having to support these multiple incompatible product lines,” said Dag Spicer, chief content officer for the Computer History Museum. In 1961, IBM realized it needed a new a new approach. A task force of top IBM engineers met in secret to figure out how to build the next generation of IBM computers.

In April 1964, IBM introduced the computer the task force had designed, System/360. During one of my programming classes, the IBM SE read the announcement. There were six different models, with more to come, with varying processing power and memory capacity. The most significant feature of System/360 was its compatibility across multiple models, ensuring compatibility in terms of software and peripherals across all models. This meant that customers could upgrade or expand their systems without needing to rewrite or replace existing software and ended the distinction between commercial and scientific computers.

System/360 revolutionized the computing industry and became a huge success for the company; IBM’s president, Tom Watson Jr., son of the founder, terminated the other IBM computer lines and put the company’s full force behind the System/360. Orders for System/360 quickly exceeded the forecasts, with more than 1,000 purchased in the first month. (There’s an anecdote suggesting that Thomas J. Watson Sr., the founder of IBM, once stated that he believed there was a world market for only about five computers, but there is no evidence that he made such a statement. In the early days of computing, the potential applications and demand for computers were not fully understood, and it’s unlikely that anyone could have accurately predicted the future ubiquity of computers.) IBM’s revenue rose from $3.6 billion in 1965 to $8.3 billion by 1971. Through the 1970s, more than 70 percent of mainframes sold were IBM’s. By 1982, more than half of IBM’s revenue came from System/360.

To me, who was writing programs for an IBM 1401 with a 16K memory, a computer with 524K or more sounded fantastic. System/360’s impact can be measured by more than just the success it brought to IBM. “IBM was where everyone wanted to work,” said Margaret McCoey, an assistant professor of computer science at La Salle University in Philadelphia. That included me; my first job after college was at IBM in Kingston, New York. “Back then, it was a tiny cult of people…the rest of the world didn’t know what we did. It was very arcane and obscure,” Greg Beedy, a 45-year veteran of working on mainframes. “Even the word ‘software’ was not that well-known.” After my 40-year career in “IT,” that’s my feeling exactly.

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Mark Berg is a community activist in Adams County and a proud Liberal. His email address is

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