How to Use CALL INTERRUPTX to Get Name of Current Directory (50228)

MORE INFORMATION

MS-DOS interrupt 21 hex function 47 hex returns an ASCIIZ string that describes the name of the current directory and the path from the root to the current directory. An ASCIIZ string is a series of ASCII characters terminated by a null byte. A null byte or null character is a 1-byte data item (a char in C) that has the value zero. It is the first character on any ASCII chart.

The "current directory" is the subdirectory that you are currently working in. The MS-DOS CHDIR (CD) command is used to change the current directory.

Note: It is necessary to use the CALL INTERRUPTX statement to call this DOS function. This is not possible with the CALL INTERRUPT statement. CALL INTERRUPT does not allow a program to change the value of the DS or ES registers. CALL INTERRUPTX allows both DS and ES to be set.

Code Example

REM $INCLUDE: 'qb.bi'
' For Basic PDS 7.00 and QBX.EXE the include file is 'QBX.BI'

DIM InRegs AS RegTypeX
DIM OutRegs AS RegTypeX
DIM CurrentDirectory AS STRING * 64

CurrentDirectory = STRING$(64, CHR$(32))   '32 is ASCII for SPACE
InRegs.Ax = &H4700                       'Function Number     in AH
InRegs.Si = VARPTR(CurrentDirectory)     'Offset of Variable  in SI
InRegs.Ds = VARSEG(CurrentDirectory)     'Segment of Variable in DS
InRegs.Dx=0                              'Drive Number        in DX
                                         '(0=default, 1=A, etc.)
CALL INTERRUPTX(&H21, InRegs, OutRegs)
CLS
PRINT "Current Directory = " + RTRIM$(CurrentDirectory)
END