Add a new KILLDSKIO environment variable #98
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When this variable is set to "ON" (case insensitive) the 512 byte buffer that is normally allocated for the DSKI$ and DSKO$ BASIC commands won't be allocated when starting the BASIC environment, thus these 512 bytes will be gained back for BASIC programs. This implies that the DSKI$ and DSKO$ commands will be disabled (they will throw "syntax error").
PATHNAME can't be zero as it's used as a pathanme buffer in BASIC. Also set DIRBUF to the same value for compatibility.
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Add a new KILLDSKIO environment variable to disable DSKI$ and DSKO$ When set to "on", the 512 byte buffer for DSKI$ and DSKO$ won't be allocated, and the commands will be disabled.
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If an environment variable named
KILLDSKIOexists with a value ofON(case insensitive) when the BASIC environment is started, the 512 byte buffer that is normally allocated as a sector buffer for theDSKI$andDSKO$commands won't be allocated, thus these 512 bytes will be gained back for BASIC programs. This implies that theDSKI$andDSKO$commands will be unavailable (they will throw "syntax error").This may be useful to load memory-intensive BASIC programs, and compensates for the fact that Nextor allocates about 230 extra bytes in page 3 than MSX-DOS 2.
When this mechanism is used to disable
DSKI$andDSKO$theDIRBUFvariable (&HF351), which holds the address of the 512 byte buffer where these commands read and write sectors, will have the same value asSECBUF(&HF34D), which is a generic sector buffer used internally by Nextor; and the same goes forPATHNAM(&HF33B), a buffer used by BASIC to parse pathnames for commands likeFILES. This shouldn't be a problem in most cases, but for robustness it's recommended to use this feature only when that extra memory is absolutely necessary.