Make an iPhone app for your own private/personal use?

Make an iPhone app for your own private/personal use?

Yes

Think about this:

While you are working on developing the app, YOU are the only one who is using it.

I don't see why you couldnt

Absolutely. You can even send it to whomever you want.

With the first PCs, we got books explaining how to code our own apps it is the same nowadays, only the books and programming tools don't come along with the device anymore.

I tend to think so, while I know it for sure if the question applies to Android, which can side-load in stock Google standard, which entirely bypasses Google Play, answer to this question is entirely different for Apple.

iOS products are more restrictive by default. Apps all need to go through App Store, and while I can't believe Apple lags behind Google on developer-restricted testing and running, you may need to pay for a Developer Account even for such insignificant personal use. Let along Apple is more restrictive on top of all other restriction in that Apache Cordova warned you to be aware of the nativity requirement.

All of that can theoretically resolved by jailbreaking the iOS device intended to run, which I overheard enables side-loading and effectively brings it inline to what Android already offers without modification.