Removing the Hidden File Attribute (67941)

MORE INFORMATION

The method described below uses DEBUG to create a small program that removes the hidden attribute from a file. This method should be used only as a last resort.

1. At the MS-DOS prompt, type the following commands:

      DEBUG
      A 100
      mov dx,116
      mov ax,4300
    
      int 21
      and cx,fffd
      mov dx,116
      mov ax,4301
      int 21
      int 20
      <ENTER>
      E 116 'filename' 0   <------- replace "filename" with the path
      G                             and filename of the target file.
                                    Example: e 116 'C:\DATA\TEST.DAT' 0
   						

   When you type the command "G," DEBUG executes the section of code in memory. If you have typed everything correctly, the message "Program terminated normally" is displayed.
2. Type Q to quit DEBUG, then verify that the file is no longer hidden.

Code Explanation

The following is a detailed description of the preceding code:

mov dx,116     ; load the offset to filename into dx
mov ax,4300    ; load get/set file attributes function number into ax
 
int 21         ; call DOS interrupt 21H to read attribute information
 
and cx,fffd    ; strip off only hidden attribute bit
mov dx,116     ; load the offset to filename into dx
mov ax,4301    ; load get/set file attributes function number into ax
 
int 21         ; call DOS interrupt 21H to write attribute information
int 20         ; terminate program
				

The program begins by calling Int 21H function 43H to get the current file attribute. The attribute byte is returned in register CX, which is then ANDed with hex FFFD to reset bit 1. The program calls the get/set file attribute function again to write the attribute in register CX to the file.