QBASIC - maskinkode - array - INT21 - Current Drive and Directory gox.gif (837 bytes)MASM: Qbasic - INT21

Det aktuelle drev og den aktuelle sti kan vises med API funktionerne:

 

Basic-koden

Definitions
TYPE Tregs
  ax AS INTEGER
  bx AS INTEGER
  cx AS INTEGER
  dx AS INTEGER
  si AS INTEGER
  di AS INTEGER
  ec AS INTEGER
END TYPE
  
DECLARE SUB init ()
DECLARE SUB Int21h ()
DECLARE FUNCTION Ztrim$ (s AS STRING)
DECLARE FUNCTION Lo% (w%)
DECLARE FUNCTION CurDrive$ ()
DECLARE FUNCTION CurDir$ ()
DECLARE FUNCTION CurPath$ ()
  		loads machine code
calls Int21
trims a zero-terminated string
returns low byte of Integer
returns Current Drive - fx "C"
returns Current Directory - fx "PROG\BAS\QB"
returns Current Path - fx "C:\PROG\BAS\QB"
DIM SHARED i21 AS STRING * 80
DIM SHARED r AS Tregs
DIM SHARED int21 AS INTEGER		 buffer for machine code
cpu registers
machine code offset in data segment
 
Program
init
    
PRINT CurPath$
C:\PROG\QBASIC\P\MC\INT\21H
 
Subroutines and Functions
SUB init
  int21 = VARPTR(i21)
  BLOAD "int21.bin", int21
END SUB
  
 
  Maskinkoden i int21.bin >MASM: Qbasic - INT21
  
SUB Int21h%
  CALL ABSOLUTE(r, int21)
END SUB
  
FUNCTION Ztrim$ (s AS STRING)
  p% = INSTR(s, CHR$(0))
  IF p% THEN
    Ztrim$ = LEFT$(s, p% - 1)
  ELSE
    Ztrim$ = s
  END IF
END FUNCTION
    s er en STRING, som indeholder en 0-afsluttet (zero-terminated) tekst.
 
Funktionen returnerer teksten fra første tegn til lige før det afsluttende 0-tegn.
  
FUNCTION Lo% (w%)
  Lo% = &HFF AND w%
END FUNCTION
    Returnerer den lave byte i en Integer
  
FUNCTION CurDrive$
  r.ax = &H1900
  Int21h
  CurDrive$ = CHR$(65 + Lo(r.ax))
END FUNCTION
     
INT 21 function 19h : Get Default Drive

Drive returned in AL (0=A, 1=B, 2=C, ... )
  
FUNCTION CurDir$
  DIM Dir AS STRING * 128
  r.ax = &H4700
  r.dx = 0
  r.si = VARPTR(Dir)
  Int21h
  CurDir$ = Ztrim$(Dir)
END FUNCTION
     
Buffer for Directory string
INT 21 function 47 : Get Current Directory
0 : Default drive
Address of buffer

Trim the returned zero-terminated string
  
FUNCTION CurPath$
  CurPath$ = CurDrive$ + ":\" + CurDir$
END FUNCTION