> TempleOS has its own programming language, HolyC. The whole operating system is written in it, except for x64 assembly in the lower-level parts. Perhaps unexpectedly, the same language is also used for the shell. … There is no built-in calculator application, because the shell itself is one. Just enter 5+7 on the command line and you'll get the answer. You can even go further than this and use the shell as a REPL to build entire programs in.
> TempleOS's unified hypertext really shines when presented in the shell. From the command-line, you can call Uf("Foo") to disassemble a function, and each symbol printed will be hyperlinked in the shell window. Click on it to go to the source. objdump can't do that.
> The most notable feature of TempleOS is its ubiquitous hypertext system, DolDoc. This is the foundation for the both the shell and the text editor. Unlike Unix which represents everything via plain-text, everything in Temple is stored in DolDoc format … You can store images (and even 3D meshes) directly into documents. You can put macros in there: hyperlink commands that run when you click on them. So if you want to build a menu or launcher, you just make a new text document and put links in it.
And so on.