CLASSIC DEVICES

Relive the world of data entry by punching holes in paper or some leftover Christmas cards with the ever-so-retro Mike Bedford.

OUR EXPERT

Mike Bedford despite being vintage hardware himself, feels no nostalgia at all for these ancient means of data entry.

T he exponential increase in performance since the early days of computing is surely staggering. Indeed, our occasional articles on the history of computing have illustrated how speed, memory capacities and storage capacities have increased by leaps and bounds. Perhaps somewhat less obvious is that this trend has gone hand in hand with obsolescence. So, hardware that was once an integral part of the computing scene is no longer with us.

Punch cards, by which we mean small sheets of cardboard into which holes could be punched, might not sound like the sort of thing that has any place in the world of electronic computing. Indeed, it’s interesting to speculate on whether they ever would have had if it weren’t for one important fact: the punch card wasn’t devised for use with computers but was something that already existed, more or less. Used, most famously, by Joseph Marie Jacquard, punch cards were first used for controlling looms in textile mills as long ago as 1804. By the end of the 19th century, though, they were being used for data storage. And in the first part mid-20th century, they were being used for creating, sorting and tabulating data. In fact, IBM was a major player in the market for punch card data processing in this pre-computer era.

Earlier punch cards differed, but the punch card that became synonymous with mainframe computers was introduced by IBM in 1928 and is often referred to as the 80-column IBM format card. These cards were a bit larger than seven inches by three, specifically 187mm by 83mm, and supported rectangular holes. As a card was punched, a graphical representation of each character was printed across the top of the card. At the same time, the positions in the vertical column below each printed character would be punched to create holes. The presence or absence of holes represented the character’s binary code.

That binary code was largely based on the EBCDIC encoding scheme, which was actually designed with punch cards in mind. We’re not going to get embroiled in the details, but if you want to know more so you can try your hand at one of our suggested coding projects, you’ll easily find the low-down. What we will say, though, is that although there were 12 punching positions in each column, only 64 characters were supported. Like so many peripherals of the ’60s and ’70s, therefore, only upper-case letters were supported. We rather suspect that the limited character set was to ensure that no more than three holes were present in any column. More holes, we gather, would have weakened the card and increased the likelihood of it jamming in a reader.