Basics of the Unix assembler syntax

Lines starting with " are comment lines

. is the location counter, where the next code or constant will be placed
.. is the relocation counter

t = 0		Sets a built-in variable to this value without generating any machine code.
		Variables so far are . .. and t. Not sure what t's purpose is yet.

orig:		is a label. It looks like labels can have dots in them.
		Dots seem to separate structures and fields, e.g. u.base
		but there are some symbols that start with dots, e.g. .seek

jms copy; 10; u.rg+2; 6		Semicolons separate instructions and
				word expressions that follow the instruction

				Some expressions are 0:0, not sure about this.
				Is it two 9-bit fields? No idea

jmp 1f		Jump back to the closest 1:	label
jmp 1b		Jump forward to the closest 1:	label

Some lines are indented differently to others e.g.

	jms betwen; o10000; o17762
	   jms error
	dac .+1

I think this is to indicate the skip logic, but it plays no part in the assembly syntax.

-1 occurs instead of instructions, so it looks like the assembler allows
literal constants at any time.

String literals seem to be two characters decorated with < > characters, e.g.
"ab" is <a>b. I'm guessing these are placed as pairs in one word. The syntax
is confusing, because I've also seen <no> ; 040 ; <fi> ; <le>; <s 012 which
appears to mean "no files\n".

Looks like a line can contain multiple labels, e.g. o12: d10: 10

Numeric literals: 0xx are octal values, [1-9]xx are decimal values.