The screen is divided in three sections or panes: The byte offset (extreme left), the hex pane (middle), and an ascii pane (right) which shows as printable characters those bytes in the hex pane. On an 80 column terminal there will be sixteen hex values and their ASCII values on each screen line. Note that (as one would expect) the first byte has the offset `0' (zero).

You can toggle between the hex and ascii windows with the tab key (TAB). Toggling between these two windows does not change the current position (offset) within the file.

No ``lines'' concept: Files are treated as one long stream of bytes. The characters ``newline'' and ``carriage return'' are not special, id est they never mark the end of lines. Therefore the lines on the screen do not represent lines in the usual way. Data is broken across screen lines arbitarily. As a consequence there are no commands in bvi from ex or vi that are based on line numbers, eg ``dd'', ``yy'', `C', `S', `o', `O'. This also changes the meaning of ``range'' before the ``:write'' command to a byte offset, ie the command ``:100,200w foo'' writes all *bytes* (not lines) from offset 100 to offset 200 to the file ``foo''.

No ``text objects": There are also no text-specific arrangements like words, paragraphs, sentences, sections and so on.

Extended ``ruler": The bottom line of the screen shows the current address (byte offset) and the current character in these notations:

        octal, hexadecimal, decimal and ascii.

     .    any character
     []   set of characters
     *    zero or more occurrences of previous char or set

        \n   newline
        \r   return
        \t   tab
        \0   binary zero

Changing the length of data (insertion, deletion) moves the data to other addresses; this is bad for many cases (eg. databases, program files) and is thus disabled by default. You can enable this commands by typing

       :set memmove

BVI Modes:

Command Mode (Normal Mode):

Input is treated as command. Note that command mode is the default mode after startup and after escaping from input mode. Use ESC (escape) to cancel a partial (uncompleted) command.

Input Mode:

Input is treated as replacement of current characters or (after the end of the file) is appended to the current file. This mode is entered from command mode by typing one of `i', `I', `A', `r', or `R'. You can enter the characters from the keyboard (in the ASCII window) or hexadecimal values (in the HEX window). Type TAB to switch between these two windows. Type ESC to finish the current input and return to command mode. Type CTRL-C to cancel current command abnormally.

Command line mode (Last Line Mode or : mode):

Similar to vi, this mode is entered by typing one of the characters : / ? \ # ! The command is terminated and executed by typing a carriage return; to cancel a partially typed command, type ESC to cancel the current command and return to command mode.

TERMINOLOGY

COMMAND SUMMARY

Abstract:
  Arrow keys move the cursor on the screen within the current window.

Sample commands:
  :version    show version info
  <- v ^ ->   arrow keys move the cursor
  h j k l     same as arrow keys
  u           undo previous change
  ZZ          exit bvi, saving changes
  :q!         quit, discarding changes
  /text       search for text
  ^U ^D       scroll up or down

Counts before bvi commands:
  Numbers may be typed as a prefix to some commands.
  They are interpreted in one of these ways.

  screen column       |
  byte of file        G
  scroll amount       ^D  ^U
  repeat effect       most of the rest

File manipulation:
  ZZ          if file modified, write and exit;
              otherwise, exit
  :w          write changed buffer to file
  :w!         write changed buffer to file, overriding
              read-only ("forced'' write)
  :q          quit when no changes have been made
  :q!         quit and discard all changes
  :e file     edit file
  :e!         re-read current file, discard all changes
  :e #        edit the alternate file
  :e! #       edit the alternate file, discard changes
  :w  file    write current buffer to file
  :w! file    write current buffer to file overriding
              read-only (this ``overwrites'' the file)
  :sh         run the command as set with option ``shell'',
              then return
  :!cmd       run the command cmd from ``shell'', then
              return
  :n          edit next file in the argument list
  :f          show current filename, modified flag,
              current byte offset, and percentage of
              current position within buffer
  ^G          same as :f

Additional edit commands
  You can insert/append/change bytes in ASCII/binary/decimal/ hexadecimal or octal representation. You can enter several (screen) lines of input. A line with only a period (.) in it will terminate the command. You must not type in values greater than a byte value. This causes an abandonment of the command. Pressing the CR key does not insert a newline - character into the file. If you use ASCII mode you can use the special characters \n, \r, \t and \0.

  :i aCR      insert bytes (ASCII) at cursor position
  :a bCR      append bytes (Binary) at end of file
  :c hCR      change bytes (hexadecimal) at cursor position

Command mode addresses
  :w foo         write current buffer to a file
                 named ``foo''
  :5,10w foo     copy byte 5 through 100 into as
                 file named foo
  :.,.+20w foo   copy the current byte and the next
                 20 bytes to foo
  :^,'aw foo     write all bytes from the beginning
                 through marker `a'
  :/pat/,$ foo   search pattern pat and and copy
                 through end of file

Positioning within file:
  ^B      backward screen
  ^F      forward  screen
  ^D      scroll down half screen
  ^U      scroll up   half screen
  nG      go to the specified character
          (end default), where n is a decimal address
  /pat    next line matching pat
  ?pat    previous line matching pat
  \hex    jump to next     occurrence of hex string hex
  #hex    jump to previous occurrence of hex string hex
  n       repeat last search command
  N       repeat last search command, but in opposite
          direction

Adjusting the screen:
  ^L      clear and redraw screen
  zCR     redraw screen with current line at top of screen
  z-      redraw screen with current line at bottom of
          screen
  z.      redraw screen with current line at center of
          screen
  /pat/z- search for pattern pat and then move currents
          line to bottom
  ^E      scroll screen down 1 line
  ^Y      scroll screen up   1 line

Marking and returning:
  mx      mark current position with lower-case letter x
          Note: this command works for all lower-case letters
  `x      move cursor to mark x in ASCII section
  `x      move cursor to mark x in HEX section
  `'      move cursor to previous context in ASCII section
  ``      move cursor to previous context in HEX section
  Line positioning:
  H           jump to first      line on screen ("top")
  L           jump to last       line on screen ("low")
  M           jump to middle     line on screen ("middle")
  -           jump onto previous line on screen
  +           jump onto next     line on screen
  CR          same as +
  DOWN or j   next     line, same column
  UP   or k   previous line, same column

Character positioning:
  ^           first byte in HEX window
  $           end of screen line
  l or RIGHT  jump onto next byte (within current
              screen line)
  h or LEFT   jump onto previous byte (within current
              screen line)
  ^H          same as LEFT
  space       same as RIGHT
  fx          find next     occurrence of character x
  Fx          find previous occurrence of character x
  n|          jump onto nth byte/character within current
              line

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