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Diffstat (limited to 'unprotbas.rst')
| -rw-r--r-- | unprotbas.rst | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/unprotbas.rst b/unprotbas.rst index 9a9a47d..d0ba0dc 100644 --- a/unprotbas.rst +++ b/unprotbas.rst @@ -175,8 +175,8 @@ Bad next-line pointer after LOADing such a file, *nothing* will work (even pressing RESET won't get you out of it). The only way to use such a program is to use the RUN command with a filename, and if the program ever exits - (due to END, STOP, an error, or the Break key), BASIC will get stuck - again. + (due to END, STOP, an error, Break key, or even System Reset), BASIC + will get stuck again. This doesn't *have* to be done with the last line in the program. The "poisoned" line could be followed by more lines of @@ -186,9 +186,16 @@ Bad next-line pointer the STMCUR pointer used by BASIC, which holds the address of the line of tokenized code currently being executed. - **unprotbas** fixes this simply by calculating what the pointer - should be (based on the tokens in the line) and changing it. No - information is lost by doing this. + Each statement in the line also has a statement-length byte. For + lines with only one statement, its value is the same as the line + length. For lines with multiple statements (separated by *:*), it's + a pointer to the next statement, counting from the start of the + current line. For the last statement on a line, it's a pointer to + the next line of code, meaning it's identical to the line length. + + **unprotbas** fixes bad line lengths by setting the line length to + the statement length of the last statement. No information is lost + by doing this. The program **UNPROTEC**, from the *Pirate's Treasure Chest*, can fix bad pointers in protected programs, though it doesn't do @@ -227,6 +234,9 @@ longer exist. **unprotbas** will generate them, according to these rules: The first 26 array variables will be *A(* to *Z(*, then *A1(* to *A9(*, *B1(* to *B9(*, etc. +Note that array variables have only the *(* as part of the name. The +closing *)* is "cosmetic" and not part of the actual name. + To properly reverse-engineer the protected program, it's necessary to assign meaningful variable names. **unprotbas** isn't smart enough to do this for you, but it can semi-automate the process. |