Assembly Language – Why Donald Knuth Writes TAOCP Using Assembly

It is a tongue-in-cheek mockery of an earlier meme about "real programmers" which is a variation of the "no true Scotsman" fallacy and "real men don't eat quiche" which was a very popular book.

http://c2.com/cgi/wiki?RealProgrammer

Original thread where Wall stated this.
Monty Python version, The Four Yorkshiremen is a mockery of this whole thing.

"Real programmers" don't need high level languages, and The Story of Mel is the exemplar of this. And it was uphill both ways!

for the very first assembler ever written (i.e. in history), wouldn't it need to be written in machine code

Not necessarily. Of course the very first version v0.00 of the assembler must have been written in machine code, but it would not be sufficiently powerful to be called an assembler. It would not support even half the features of a "real" assembler, but it would be sufficient to write the next version of itself. Then you could re-write v0.00 in the subset of the assembly language, call it v0.01, use it to build the next feature set of your assembler v0.02, then use v0.02 to build v0.03, and so on, until you get to v1.00. As the result, only the first version will be in machine code; the first released version will be in the assembly language.

I have bootstrapped development of a template language compiler using this trick. My initial version was using printf statements, but the first version that I put to use in my company was using the very template processor that it was processing. The bootstrapping phase lasted less than four hours: as soon as my processor could produce barely useful output, I re-wrote it in its own language, compiled, and threw away the non-templated version.