Hardware hacking
The term hacking has bad connotations, thanks to computer miscreants, but electronics has always been about hacking.
If you want something that doesn't already exist, you hack together some parts to build what you want (it's often a serious of experiments until you find something that works the way you need). If you have something that doesn't work in the way you need, or doesn't work very well, you can hack into it and modify it, rather than just put up with something that's an annoyance. When equipment fails, repairs are often a lot of hacking to find and fix the fault, particularly when you don't have schematic diagrams to follow and have to make up custom circuits to replace parts that aren't available. And in the olden days many people got into electronics by pulling apart their telephone or radio, and finding out how it worked by experimentation.
On this website, just to list some of the things I've hacked:
- substituting alternative power amplifier modules for the original failed ones in a Rotel RX500 amplifier and a Vox Mini3 guitar amp
- modified ANKO computer keyboards to have less insane coloured illumination and add an audible warning for the caps lock key
- modified camera lens zoom controllers that weren't wired correctly, or I needed a different connector fitted
- bodged together a LED lightbar for my piano since I couldn't find anything ready-made that met my needs
- modified the metering in a Yamaha MG12/4 audio mixer to be actually useful
- modified Panasonic AG7650/7750 S-VHS VCRs with design flaws and annoyances
- modified Panasonic WV5300 CRT monitors (adding tally lights and converting the scan height for widescreen display)
- added phantom powering to Nakamichi microphones
- modified a piano bench that was too short (added adjustable feet to it)
- modified Xtreme accessories FS310 and Yamaha FC5 piano pedals to suit my needs.
- how my Technics organ works (multiple modifications and repairs)
- the viewfinders (and other things) in Panasonic F15 and F250 cameras
- my Yamaha P45 plastic piano (adding an option to not shut off the speakers when a lead is plugged into the headphone socket)
Software hacking
A lot of software is also hacking. Amateur programmers who haven't been trained will kludge things together, often in ways that are not great, just trying things out until the manage to do the job they set out to do, and not adequately testing how they react under adverse conditions. And that isn't just personally created software, a lot of software used by the public is badly written.
There's also the modification aspect I mentioned about electronics. It's possible to modifying existing programs. Open source software can be modified and recompiled, but even closed‑source software can be decompiled modified and recompiled, or the binary directly hacked if you can discover the structure of it.
But mostly computer hacking is known for miscreants who look for flaws in software that they can exploit for nefarious purposes.