Alan Turing, for World War 2 using the enigma machine. Before that it was Nevil Maskelyne who hacked into Morse code.
Hacking is nothing at all to do with breaking in to systems.
(Breaking it to stuff is "cracking", but TV & movie writers think hacking sounds better…)
Hacking is about creating things – it comes from re-using parts – "hacking apart" other gear and building your own things from it. There were thousands of computer hackers worldwide, all building gear and exchanging ideas through early magazines.
I was / am a _real_ computer hacker, from the early 70s onward.
(Not a cracker and not doing anything illegal – though there were no specific laws covering such things until around 1990 or so, I think.. People causing harm such as phone phreakers causing too much trouble were prosecuted for such as "Theft of electricity").
In the early days of computers, special parts were extremely rare and ludicrously expensive. The only way for a computer enthusiast to get parts was from surplus and scrap gear, taking it apart to get the bits needed.
After you built your own machine, you had to program it..
Memory was incredibly expensive. The first machine I built (that I got properly working – many attempts on) had 256 BYTES (not megabytes or kilobytes, just 256 locations) total RAM.
I wrote games in that and sold them in one of the early enthusiast magazines; hand-typed listings of machine code/assembly language, then photocopied and posted.
(A printer cost more than a car).
I had to build the computer terminal to communicate with it – that was needed before I could get the computer itself working. It was a boxful of simple logic ICs that gave a 40 character per line text display through a TV, plus a scrap keyboard connected to a built up interface.
It worked through RS232 serial, which meant it could also be connected to a telephone modem (again, re-built salvage, a monstrous boxful of discrete components and coils/transformers) – and you could "dial in" to other computer systems.
Back then, no one thought of doing anything nasty and quite a few companies would cheerfully give the phone numbers for their computer rooms & you could talk with their people, almost guaranteed to also be enthusiasts – & if you were lucky you could dial in to their systems and chat online or look through the system itself.
Some had their own bulletin boards to exchange ideas, rather quicker than monthly books…
Each of those little boards has a few transistors, diodes, resistors to make up simple logic gate functions.
It would probably have cost around $250,000 new.
This would be the type of thing the junk parts came from – a 1950s multi-million-dollar mainframe computer:
(Just a few cabinets from an overall system scattered about that photo).
I don't have any gear or photos left from the early 70s; this is rather newer (early 90s) & much more powerful but uses the same techniques as I used back then, genuine "hacker built" computer equipment:
Robert Tappan Morris …
The Morris worm… source code is available online…