INT 16 U - PC Tools v8+ VSAFE, VWATCH - GET/SET OPTIONS
        AX = FA02h
        DX = 5945h
        BL = new parameter flags (see below)
Return: CF clear
        DI = 4559h
        CL = old value of parameter flags

Bitfields for parameter flags:
 bit 7  Protect executable files
 bit 6  Protect FD boot sector
 bit 5  Protect HD boot sector
 bit 4  Boot sector viruses
 bit 3  Check executable files
 bit 2  General write protect
 bit 1  Resident
 bit 0  HD Low level format

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