Did you ever saw a char and thought: "Damn, 1 byte for a single char is pretty darn inefficient"? No? Well I did. So what I decided to do instead is to pack 5 chars, convert each char to a 2 digit integer and then concat those 5 2 digit ints together into one big unsigned int and boom, I saved 5 chars using only 4 instead of 5 bytes. The reason this works is, because one unsigned int is a ten digit long number and so I can save one char using 2 digits. In theory you could save 32 different chars using this technique (the first two digits of an unsigned int are 42 and if you dont want to account for a possible 0 in the beginning you end up with 32 chars). If you would decide to use all 10 digits you could save exactly 3 chars. Why should anyone do that? Idk. Is it way to much work to be useful? Yes. Was it funny? Yes.
Anyone whos interested in the code: Heres how I did it in C: https://pastebin.com/hDeHijX6
Yes I know, the code is probably bad, but I do not care. It was just a funny useless idea I had.
No, it doesn't. It can't know if you need a full set of characters or only a subset of them, so it can't optimize like this. If you know you only need to represent capital letters and a few punctuations, you can do something like the OP. The compiler has to assume you could need the full range of characters represented by the format though (especially since it doesn't even know if you'll continue to use them as characters—you may want to do arithmetic on them).
Definitely premature optimization, and not even ose to optimal either. It's next to useless, but I think the OP was just having fun.