proc main
   string sLine1                                ;Line of data read from file 1
   string sLine2                                ;Line of data read from file 2
   integer iLen                                 ;Holds length of sLine2
   long lLen                                    ;Long variable used in disk operations

   if fopen 0 "file1.txt" READ                  ;If file 1 is opened successfully
      if fopen 1 "file2.txt" READWRITE          ;If file 2 is opened successfully
         while not feof 0                       ;While data exists in file 1...
            fgets 0 sLine1                      ;Read line from file 1
            while not feof 1                    ;While data exists in file 2...
               fgets 1 sLine2                   ;Read line from file 2
               if strcmp sLine1 sLine2          ;If lines are identical
                  strlen sLine2 iLen            ;Get length of line
                  lLen = iLen                   ;Save in long variable for use in disk operations
                  fseek 1 (-lLen) 1             ;Back up file pointer by length of current line
                  fdelblock 1 iLen              ;Delete current line from file 2
                  ftell 1 lLen                  ;Get current file pointer
                  fclose 1                      ;Close file 2
                  fopen 1 "file2.txt" READWRITE ;Reopen file so we can continue checking the remainder
                  fseek 1 lLen 0                ;Set file pointer to previously-read location
               endif
            endwhile
            fclose 1                            ;Close file 2
            fopen 1 "file2.txt" READWRITE       ;Reopen for next pass through file 2
         endwhile
      endif
   endif
   fclose 0
   fclose 1
endproc