Was it ever possible to take an actual existing punch card reader, and hack a connection to hook it up to a computer?
No, why? The existing tabulating machine was all about parallel processing.
Or was it the case that yes the existing cards could be reused, but to use them with computers required designing and building all new equipment?
No. Of course not. But 'using' equipment is more than just plugging it in.
It's no either/or, but one as well as the other. All are parts of a process. The process is more than a single machine or computer and like with every change, a gradual one, possibly were bottlenecks are, is preferred over a green field approach. In turn one must look at the gradual changes that happened.
Before (electronic) computers tabulating offered process steps like this:
- Data gets collected on punch cards, either
- by being outputted by previous runs or
- by being keyed in with a key punch
- Processing happened
- Data gets outputted
- Into new cards by a card punch
- Onto paper, by a printer, which in turn could be handled by
So there are a lot of tools and steps for data processing to be used. And while most (andfinally all) can be replaced by a computer and additional devices, a new computer does also ft nicely into the existing landscape by first only replacing the tabulator. To do so he needs to be able to input and output cards, nothing else.
Data gets still collected by halls of young girls typing them in (or grumpy old men in an autoparts store), stacks geht moved to the computer, processed there and then moved over to a printer (printing tabulator). So he could replace all, or most of the machinery, couldn't he?
Well, yes, but why occupying precious processing time of that machine with a mundane task like
- sorting cards, when there's still the existing sorter?
- searching for records, when there is still a dedicated sorter?
- searching more convenient when there is still a collator?
- not to mention merge by simply stacking cards by hand?
Why blocking the computer with handling an (additional to pay for) printer, when that could still be done with the old printing tabulator, now plugged for straight printing out whatever is on a card?
Any reasonable manager would only use the computer to replace the most strained device, the bottleneck - keep in mind, if there is no bottleneck, one doesn't need a new computer in the first place - and leave all the other parts of the process as they are.
Of course, with faster machines and management seeing the benefits of buying a computer, it got additional card readers and card punches and sorters as well as collators went out of use (*1). Interpreters got replaced not by computers, but by card punches that could as well print and new key punches with the same ability.
The last one is an important point. with having a computer, it first extended and later gradually replaced the more complex separate machines, but need for key punches dod not vanish, but increas, so much that IBM (and others) introduced new models not only with the /360 in 1964 (029), but new designs as late as 1971 with the IBM 5924 Kanji keypunch and the transistorized and programmable 129.
*1 - Still, I've seen sorters used, or at least on stand by as late as 1978.