01 done

01/Makefile

@@ -0,0 +1,7 @@
+all: out01 README.html
+out01: in01 out00
+	./out00
+out00: in00
+	../00/hexcompile
+%.html: %.md
+	markdown $< > $@

01/README.md

@@ -0,0 +1,345 @@
+# stage 01
+
+The code for the compiler for this stage is in the file `in00`. And yes, that's
+an input to our previous program, `hexcompile`, from stage 00! To compile it,
+run `../00/hexcompile` from this directory. You will get a file, `out00`. That
+is the executable for this stage's compiler. Run it (it will read from the file
+`in01` I've provided) and you'll get a file `out01`. That executable will print
+`Hello, world!` when run. Let's take a look at the input we're providing to the
+stage 01 compiler, `in01`:
+
+<pre><code>
+|| ELF Header
+;im;01;00;00;00;00;00;00;00 file descriptor for stdout
+;JA
+;im;bc;00;40;00;00;00;00;00 address of string "Hello, world!\n"
+;IA
+;im;0e;00;00;00;00;00;00;00 number of bytes to output
+;DA
+;im;01;00;00;00;00;00;00;00 syscall #1 (write)
+;sy
+;zA
+;DA exit code 0
+;im;3c;00;00;00;00;00;00;00 syscall #60 (exit)
+;sy
+;'H;'e;'l;'l;'o;',;' ;'w;'o;'r;'l;'d;'!;\n the string we're printing
+;
+</code></pre>
+
+Look at that! There are comments! Much nicer than just hexadecimal digit pairs.
+
+## end result
+
+Our 01 compiler will take a very basic "assembly" language, and output an
+executable. The input file consists of a bunch of two-character commands
+separated by semicolons. Any text after the command and before the semicolon is
+ignored (that's how we get comments), and there has to be a terminating
+semicolon.
+
+So, for example, the `sy` command outputs a syscall instruction. You can see
+`commands.txt` for a full list.
+
+`||` is a very important command. It outputs an ELF header for our executable.
+Rather than compute the correct size of the file, it just sets the "file size"
+and "memory size" members of the program header to `0x40000` (enough for a 256KB
+executable). As it turns out, Linux won't mind if the program header lies about
+how much data is in the file.
+
+If an unrecognized instruction is encountered, this compiler will
+actually print out an error message and exit, rather than continuing as if
+nothing happened! Try adding `xx;` to the end of the file `in01`, and running
+`./out00`. You should get the error message:
+
+<pre><code>
+xx not recognized.
+</code></pre>
+
+Pretty cool, huh?
+Anyways let's see how this compiler actually works.
+
+## compiler source
+
+Writing in our stage 00 language is much nicer than editing an
+executable, because it's easier to move things around, and also, we can separate
+our program into lines! Let's take a look at the start:
+
+<pre><code>
+7f 45 4c 46
+02
+01
+01
+00 00 00 00 00 00 00 00 00
+02 00
+3e 00
+01 00 00 00
+a8 00 40 00 00 00 00 00
+40 00 00 00 00 00 00 00
+00 00 00 00 00 00 00 00
+00 00 00 00
+40 00
+38 00
+01 00
+00 00
+00 00
+00 00
+01 00 00 00
+07 00 00 00
+78 00 00 00 00 00 00 00
+78 00 40 00 00 00 00 00
+00 00 00 00 00 00 00 00
+00 10 02 00 00 00 00 00
+00 10 02 00 00 00 00 00
+00 10 00 00 00 00 00 00
+</code></pre>
+
+This is the ELF header and program header. It's just like our last one, but with
+a couple of differences. First, our entry point is at offset 0xa8 instead of 0x78.
+I decided to put the data before the code this time (it made it a bit
+easier to work with), so we start a little bit later than the first byte in our
+segment.  Second and more importantly, rather than 512 bytes, our segment is
+0x21000 = 135168 bytes long! That's because we're storing a table of all the
+commands our compiler supports. This table has one eight-byte entry for each
+pair of ASCII characters. There are 128 ASCII characters, so that means it's
+`128 * 128 * 8 = 131072` bytes long. And there's a little bit of extra room for
+the actual code. Funnily enough, this large source file means that compiling our
+stage 01 compiler isn't instantaneous (remember how I said reading 3 bytes at a
+time would be slow?). On my system, it takes 0.13 seconds to run
+`../00/hexcompile`.
+
+
+- `69 6e 30 31 00` `"in01"`
+- `6f 75 74 30 31 00` `"out01"`
+- `00 00 20 6e 6f 74 20 72 65 63 6f 67 6e 69 7a 65 64 2e 0a` `"\0\0 not
+recognized."`
+- `00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00` (unused)
+
+Here's the data for our program. As you can see from my annotations, we have the
+input and output file, as well as the error message. The command part of the
+error message is left blank for now (we'll fill it in when the code is actually
+run).
+
+Okay, now we get to the actual code. The entry point is right here:
+
+- `48 b8 78 00 40 00 00 00 00 00` `mov rax, 0x400078 ("in01")`
+- `48 89 c7` `mov rdi, rax`
+- `31 c0` `mov rax, 0`
+- `48 89 c6` `mov rsi, rax`
+- `48 b8 02 00 00 00 00 00 00 00` `mov rax, 2`
+- `0f 05` `syscall`
+
+This is an `open` syscall, just like from stage 00. We're opening our input file.
+
+- `48 b8 7d 00 40 00 00 00 00 00` `mov rax, 0x40007d ("out01")`
+- `48 89 c7` `mov rdi, rax`
+- `48 b8 41 02 00 00 00 00 00 00` `mov rax, 0x241`
+- `48 89 c6` `mov rsi, rax`
+- `48 b8 ed 01 00 00 00 00 00 00` `mov rax, 0o755`
+- `48 89 c2` `mov rdx, rax`
+- `48 b8 02 00 00 00 00 00 00 00` `mov rax, 2`
+- `0f 05` `syscall`
+
+This opens our output file, just like last time.
+
+- `48 b8 03 00 00 00 00 00 00 00` `mov rax, 3 (input fd)`
+- `48 89 c7` `mov rdi, rax`
+- `48 b8 83 00 40 00 00 00 00 00` `mov rax, 0x400083`
+- `48 89 c6` `mov rsi, rax`
+- `48 b8 02 00 00 00 00 00 00 00` `mov rax, 2`
+- `48 89 c2` `mov rdx, rax`
+- `31 c0` `mov rax, 0`
+- `0f 05` `syscall`
+
+Here we read two bytes from our input file into memory address `0x400083`. Note
+that this corresponds to those two blanks bytes at the start of our error
+message.
+
+- `48 89 c3` `mov rbx, rax`
+- `48 b8 01 00 00 00 00 00 00 00` `mov rax, 1`
+- `48 39 d8` `cmp rax, rbx`
+- `0f 8c 17 00 00 00` `jl +0x17`
+
+If we actually read two bytes, jump forward past this bit of code right here:
+
+- `31 c0` `mov rax, 0`
+- `48 89 c7` `mov rdi, rax`
+- `48 b8 3c 00 00 00 00 00 00 00` `mov rax, 0x3c (exit)`
+- `0f 05` `syscall`
+- `00 00 00 00 00 00` (unused)
+
+This code is only run when the end of the file is reached. It just exits the
+program with exit code 0 (successful).
+
+- `48 b8 83 00 40 00 00 00 00 00` `mov rax, 0x400083`
+- `48 89 c3` `mov rbx, rax`
+- `31 c0` `mov rax, 0`
+- `8a 03` `mov al, byte [rbx]`
+- `48 c1 e0 07` `shl rax, 7`
+- `48 89 c7` `mov rdi, rax`
+- `48 b8 84 00 40 00 00 00 00 00` `mov rax, 0x400084`
+- `48 89 c3` `mov rbx, rax`
+- `31 c0` `mov rax, 0`
+- `8a 03` `mov al, byte [rbx]`
+- `48 89 fb` `mov rbx, rdi`
+- `48 01 d8` `add rax, rbx`
+
+This here looks at the two bytes we read in (we'll call them `b1` and `b2`) and
+computes `b1 * 128 + b2` (more specifically `(b1 << 7) + b2`). This is the index
+in our command table corresponding to the two characters from the input file.
+
+- `48 c1 e0 03` `shl rax, 3`
+- `48 89 c3` `mov rbx, rax`
+- `48 b8 00 10 40 00 00 00 00 00` `mov rax, 0x401000`
+- `48 01 d8` `add rax, rbx`
+- `48 89 c5` `mov rbp, rax`
+
+Now we compute the address of the entry in the command table. Each entry is 8
+bytes long, so we shift the index left by 3 (multiply by 8), and then add
+`0x401000`, the address of the start of the table. We store away the computed
+address in `rbp` for later use.
+
+- `48 89 c3` `mov rbx, rax`
+- `31 c0` `mov rax, 0`
+- `8a 03` `mov al, byte [rbx]`
+- `48 89 c3` `mov rbx, rax`
+- `31 c0` `mov rax, 0`
+- `48 39 d8` `cmp rax, rbx`
+- `0f 85 5a 00 00 00` `jne +0x5a`
+
+The format of each command table entry is the length of the data to output,
+stored as one byte, followed by the data. So the entry for `BA (mov rbx, rax)`
+is `03 48 89 c3`. We set the length to 0 for unused entries.
+
+So this code checks if the entry for this command starts with a zero byte. If it
+does, that means the two characters we read in don't actually correspond to a
+real command. If that's the case, this next bit of code is executed (otherwise
+it's skiped over):
+
+- `48 b8 02 00 00 00 00 00 00 00` `mov rax, 2 (stderr)`
+- `48 89 c7` `mov rdi, rax`
+- `48 b8 83 00 40 00 00 00 00 00` `mov rax, 0x400083 ("XX not recognized")`
+- `48 89 c6` `mov rsi, rax`
+- `48 b8 13 00 00 00 00 00 00 00` `mov rax, 13 (length)`
+- `48 89 c2` `mov rdx, rax`
+- `48 b8 01 00 00 00 00 00 00 00` `mov rax, 1 (write)`
+- `0f 05` `syscall`
+- `48 b8 01 00 00 00 00 00 00 00` `mov rax, 1 (exit code)`
+- `48 89 c7` `mov rdi, rax`
+- `48 b8 3c 00 00 00 00 00 00 00` `mov rax, 60 (exit)`
+- `0f 05` `syscall`
+- `00 00 00 00 00 00 00 00 00 00 00 00 00 00` (unused)
+
+This prints our error message, now filled in with the specific unrecognized
+instruction, to standard error, and exits with code 1, to indicate failure.
+
+- `48 89 eb` `mov rbx, rax`
+- `31 c0` `mov rax, 0`
+- `8a 03` `mov al, byte [rbx]`
+- `48 89 c2` `mov rdx, rax`
+
+This puts the length of the data for this command into `rdx` (the `length`
+argument to the `write` syscall is passed in `rdx`).
+
+- `48 b8 04 00 00 00 00 00 00 00` `mov rax, 4`
+- `48 89 c7` `mov rdi, rax`
+- `48 89 eb` `mov rbx, rbp`
+- `48 b8 01 00 00 00 00 00 00 00` `mov rax, 1`
+- `48 01 d8` `add rax, rbx`
+- `48 89 c6` `mov rax, rsi`
+- `48 b8 01 00 00 00 00 00 00 00` `mov rax, 1`
+- `0f 05` `syscall`
+
+Now we write the actual data for this command! Note that we add 1 to the address
+we computed earlier, to skip over the byte indicating how long the command is.
+
+- `48 b8 03 00 00 00 00 00 00 00` `mov rax, 3 (input fd)`
+- `48 89 c7` `mov rdi, rax`
+- `48 b8 83 00 40 00 00 00 00 00` `mov rax, 0x400083`
+- `48 89 c6` `mov rsi, rax`
+- `48 b8 01 00 00 00 00 00 00 00` `mov rax, 1 (length)`
+- `48 89 c2` `mov rdx, rax`
+- `31 c0` `mov rax, 0 (read)`
+- `0f 05` `syscall`
+- `48 b8 83 00 40 00 00 00 00 00` `mov rax, 0x400083`
+- `48 89 c3` `mov rbx, rax`
+- `31 c0` `mov rax, 0`
+- `8a 03` `mov al, byte [rbx]`
+- `48 89 c3` `mov rbx, rax`
+- `48 b8 3b 00 00 00 00 00 00 00` `mov rax, 0x3b (';')`
+- `48 39 d8` `cmp rax, rbx`
+- `0f 85 ae ff ff ff` `jne -0x52`
+- `e9 66 fe ff ff` `jmp -0x19a`
+
+Here we read one byte at a time from the input file, and if it's `;`, we jump
+all the way back to read the next command. Otherwise, we keep looping. This
+skips over any comments/whitespace we might have between a command and the
+following command.
+
+And that's all the *code* for this compiler. Next comes some data.
+
+First, there's a whole bunch of unused 0s. Then there's the line
+
+- `cc cc cc cc cc cc cc cc`
+
+This is only here for decoration, to mark the start of the command table (at
+address `0x401000`). It appears on line 272, so we can compute the line number
+to put each command on as `c1 * 128 + c2 + 272`, where `c1` and `c2` are the
+ASCII character codes used for the command. So, `sy` (s = ASCII 115, y = ASCII
+121) would be put on line `115 * 128 + 121 + 272 = 15113`. Sure enough, scroll
+down to line 15113, and you'll see:
+
+- `02 0f 05 00 00 00 00 00` (2 bytes long, data `0f 05`)
+
+Which is the encoding of the `syscall` instruction.
+
+You can look through the rest of the table, if you want. But let's look at the
+very end:
+
+<code><pre>
+78
+7f 45 4c 46
+02
+01
+01
+00 00 00 00 00 00 00 00 00
+02 00
+3e 00
+01 00 00 00
+78 00 40 00 00 00 00 00
+40 00 00 00 00 00 00 00
+00 00 00 00 00 00 00 00
+00 00 00 00
+40 00
+38 00
+01 00
+00 00
+00 00
+00 00
+01 00 00 00
+07 00 00 00
+00 00 00 00 00 00 00 00
+00 00 40 00 00 00 00 00
+00 00 00 00 00 00 00 00
+00 00 03 00 00 00 00 00
+00 00 03 00 00 00 00 00
+00 10 00 00 00 00 00 00
+</code></pre>
+
+This is at the position for `||`, and it contains the ELF header. One thing you
+might notice is that we decided that each entry is 8 bytes long, but this one is
+0x79 = 121 bytes long! It's okay, our code doesn't actually check that we're
+using less than 8 bytes of data, but it means that the entries for certain
+commands, e.g. `}\n` will land right in the middle of the data for the ELF
+header. But by a lucky coincidence, all those entries actually land on 0 bytes,
+so they'll just be treated as unrecognized (as they should be). So it's all
+good.
+
+## Limitations
+
+Like our last program, this one will be slow for large files. Again, that isn't
+much of a problem for us. Also, if you forget a `;` at the end of a file, it'll
+loop infinitely rather than printing a nice error message. I could have
+fixed this, but frankly I've had enough of writing code in hexadecimal. So let's
+move on to stage 02, now that we have a nicer language on our hands. From now
+on, since we have comments, I'm gonna do most of the explaining in the source file
+itself, rather than the README. But there'll still be a bit of stuff there each
+time.

01/commands.txt

@@ -1,3 +1,5 @@
+|| - ELF Header
+
 00 - Byte 00
 ..
 ff - Byte ff

01/in00

@@ -18,16 +18,16 @@ a8 00 40 00 00 00 00 00
 00 00
 01 00 00 00
 07 00 00 00
+78 00 00 00 00 00 00 00
+78 00 40 00 00 00 00 00
 00 00 00 00 00 00 00 00
-00 00 40 00 00 00 00 00
+00 10 02 00 00 00 00 00
-00 00 00 00 00 00 00 00
+00 10 02 00 00 00 00 00
-00 00 03 00 00 00 00 00
-00 00 03 00 00 00 00 00
 00 10 00 00 00 00 00 00
 69 6e 30 31 00
 6f 75 74 30 31 00
-00 00 20 6e 6f 74 20 72 65 63 6f 67 6e 69 7a 65 64 2e 0a 00 00 00
+00 00 20 6e 6f 74 20 72 65 63 6f 67 6e 69 7a 65 64 2e 0a
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 48 b8 78 00 40 00 00 00 00 00
 48 89 c7
 31 c0
@@ -16292,119 +16292,3 @@ cc cc cc cc cc cc cc cc
 00 00 03 00 00 00 00 00
 00 00 03 00 00 00 00 00
 00 10 00 00 00 00 00 00
-cc cc cc cc cc cc cc cc
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-00 00 00 00 00 00 00 00 00 00

01/in01

@@ -1,4 +1,4 @@
-||
+|| ELF Header
 ;im;01;00;00;00;00;00;00;00 file descriptor for stdout
 ;JA
 ;im;bc;00;40;00;00;00;00;00 address of string "Hello, world!\n"

bootstrap.sh

@@ -36,4 +36,15 @@ fi
 rm -f out00
 cd ..
 
+cd 01
+rm -f out0[01]
+make -s out01
+if [ "$(./out01)" != 'Hello, world!' ]; then
+	echo_red 'Stage 01 failed.'
+	exit 1
+fi
+rm -f out0[01]
+cd ..
+
+
 echo_green 'all stages completed successfully!'