Immers. This manual contains a wealth of information on the makeup
      of the Commodore format and the Disk Operating System (DOS). With
      this manual and our GCR Editor, you can achieve a new level of
      understanding.
      
      In the following instructions, we will give you all the command
      features available to you with the Kracker Hacker GCR Editor. Only
      use and study can make you proficient. Enjoy!
      
      What is GCR?
      
      When you load and save files from the C-64 to disk, they are not
      written bit for bit straight to the diskette. The Commodore 1541/71
      disk drive cannot write more than three "0" bits in a row to a
      disk, so writing a hex byte like #$06 poses a problem! Commodore
      developers created the GCR coding scheme to read and write data to
      and from the drive. It converts each four bits of hex code into 5
      bits of GCR code. For every four bytes of hex data, there are five
      GCR bytes. Lastly, this data is written at a standard rate,
      depending on its placement on the diskette. Standard Bit Rates are
      as follows: Tracks 1-17 = $60, Tracks 18-24 = $40, Tracks 25-30 =
      $20, Tracks 31-35 = $00.
      
      Commodore DOS protection is, for the most part, simply the
      placement of NON-STANDARD data on the diskette. This can be created
      by using single bytes in non-standard locations, abnormal drive
      speeds, or rewriting the format (single sectors, tracks, or the
      entire disk). By using your GCR Editor, you can obtain exact format
      information. You even have the power to duplicate many protection
      schemes on non-working backups.  Let's go through the commands
      available to you in this powerful utility. From the main start-up
      menu, choose option 3 and press RETURN.

      First Screen (Header Selection)
      
      Track Selection: Track values are entered in decimal. Values from
      1-40.5 are accepted.

      Bit Rate Selection: Press RETURN for default value, otherwise enter
      one of four bit rates ($00, $20, $40, $60).
      
      After Scan of Track: The number of headers equals the number of
      syncs on a track. Left column = GCR of first 8 bytes. The right
      column = converted GCR bytes. The message bar just above the list
      of headers gives you information about the current header the
      cursor is on. Left hand will say: Sector: xx if the current header
      is part of a standard formatted track. It will give you the sector
      number in decimal so you can use the GCR Editor like a sector
      editor. The right hand will either say DATA or HEADER, depending
      upon whether the cursor is on the data block header (starts with a

            K.J. REVEALED TRILOGY    PAGE [151]    (C)1990 K.J.P.B.