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Diffstat (limited to '02/README.md')
| -rw-r--r-- | 02/README.md | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/02/README.md b/02/README.md index 1a77e50..d09c7ca 100644 --- a/02/README.md +++ b/02/README.md @@ -71,6 +71,7 @@ plus six new ones: - `--` outputs a label's (absolute) address - `:-` outputs a label's relative address - `##` outputs a number +- `~~` outputs 255 zeros - `//` is for comments - `\n\n` does nothing (used for spacing) @@ -172,6 +173,13 @@ since `0x90` gets inserted between the "load immediate" instruction code and the `\n\n` works identically, and lets us space out code a bit. But be careful: the number of blank lines must be a multiple of 3! +In the middle of the label table, you'll find a mysterious `ff` byte. This is at the position for +the command `~~` (the end of the command table overlaps with the start of the label table). +This command is just 255 bytes of zeros. If you defined a label whose position in the label +table overlaps with these zeros, you'd screw up the command. But fortunately, this will only happen +if you include `\r` or a non-printing character in your label names. +This is so that you can have big buffers to put data in (like our label table from this compiler). + ## limitations Many of the limitations of our previous compilers apply to this one. Also, |