added POSIX AWK reference implementation

README.md

@@ -256,6 +256,8 @@ works on the platforms supporting I/O port 1 (character output).
 
 If you just want to test an implementation, assembled MU8 machine code files
 (in the plaintext format) are stored in the `examples/assembled` subdirectory.
+After loading into the REPL, you can run each of them with the `0 1 0 0 1` or
+`0 1 6 0 1` sequence.
 
 Reference implementations
 -------------------------
@@ -274,6 +276,12 @@ Reference implementations
   `fma()` call that appeared in the C99 standard. Accepts a file name to preload
   a MU8 machine code program from the OS command line. Compile the source with:
   `cc -std=c99 -O2 -s -lm -o mu808 mu808.c`
+* [POSIX AWK implementation](mu808.awk): supports the entire mu808 specification
+  sans the (non-portable) I/O port 2. Run it like this:
+  `LC_ALL=C awk -f mu808.awk [- input_program.mu8]`, where the dash-delimited
+  program file name is optional and used for preloading MU8 program files into
+  VM's memory. The Busybox AWK implementation is compact but quite slow, so use
+  it as a last resort solution when no other programming environment is available. 
 
 ### Assembler reference implementations