*** Almost Completely Superfluous Manual to ZAP 2.5 ***
*** What is ZAP ? ***
ZAP is an editor, designed to edit program files. That is why it cannot
change the length of a file, and why it displays files both in ASCII
and in hexadecimal code.
It needs very little memory ( less than 25K ) and may be used on files
of arbitrary size, to at least a megabyte.
ZAP is a 'public domain' tool.
Copy it and pass it on as much as you like.
*** Why would I need ZAP ? ***
For any number of reasons. Every time you want to know, and maybe to
change, what is in a file that is not normally readable or printable,
you will find yourself reaching for ZAP.
Other possibilities:
- Use it to change a default path in those irritating programs that
do not know where to find your hard disk or ram disk.
- Use ZAP to modify text in programs of which you do not have the
source code, e.g. to correct spelling mistakes, or to translate
messages.
- Use it to find text in programs, e.g. to look at vocabularies
of games (if they have not been encrypted).
- Use it to look for hidden messages in programs, and experience
the true hacker's thrill....
*** How do I use ZAP ? ***
Very carefully.
ZAP is a like a surgeon's knife: very handy to work with, but dangerous
unless you know exactly what you're doing. As it may take only two
keystrokes in ZAP to ruin any program, one to change a byte and one to
write the changed data back to disk, I must advise you strongly to
ALWAYS make a backup before experimenting. (Not that I ever do. But then
I'm stupid. YOU should know better.)
ZAP, however, also has the possibility to protect a file from changes
on at least four separate levels, to prevent accidental changes.
- If the disk is physically write-protected, or if the file is
read-only, ZAP of course cannot change it.
- If you specify the -r option on the commandline ZAP will not change
the file.
- If you lock the file during editing (click 'r/w' in the EDIT menu)
ZAP will not allow any changes to the file until the lock is switched
off again.
- If you use the text filter, (click 'raw' int the EDIT menu) which
displays only those bytes in the text field which are letters,
digits, or punctuation marks, you cannot modify the file until you
switch the filter off. The reason for this is to ensure that you
write only when you have full information on what you're overwriting.
- If you are in ESC mode ('ESC' displayed in the lower left corner
of the screen) you cannot make changes to the displayed data.
( Note, however, that if you first make changes in EDIT mode, then
switch to ESC mode, then get another chunk, ZAP will write the
modified chunk to disk if you did not lock the file.)
*** Starting ZAP ***
ZAP may be named either ZAP.TTP or ZAP.TOS. It may be double-clicked,
or called from a shell. If a commandline is passed to ZAP, it will be
used, or else it will start with a dialog to ask for a commandline.
In both cases the commandline must be of the same form:
[ -r ]
where is any legal TOS path/filename, and the optional
-r (or -R) the read-only option.
Examples: "c:\zap.ttp -r" will open the file ZAP.TTP in read-only mode.
"zap.ttp" will open it normally.
(If the file may be written to in TOS.)
The commandline dialog page also explains how the single-line editor
works. This single-line editor is used also for the search-string
entry, so you may want to remember how it works. Not that there is
anything difficult to it, it's all very logical.
You can move the cursor, use backspace and delete, clear the line
with and recall the original line with Undo. Pressing Return
completes input, and if the line is empty ZAP exits.
*So, the way to quit ZAP is to press at the command
line dialog. If the file cannot be opened, or if the commandline
contains the wildcards '*' or '?' ZAP gives an error message and lets
you try again.
*** The ZAP screen ***
This consists of 4 parts: menubar, parameter section, file display,
and command/message line.
The top line is the menu bar. It displays the main command options you
have at your disposal at that point.
There are two menu bars, one for the EDIT mode and one for the ESC mode.
You can see which mode ZAP is in by looking at the lower left corner
of the screen.
In EDIT mode, the menu bar shows:
- ZAP 2.5
The name and version number of the program.
Click this for some info about ZAP and for my address.
- help
Click this (or press ) to get a summary of the workings of
ZAP in edit mode.
- Esc
Click this (or press ) to switch to ESC mode.
- addr
Click this to jump to an address in the file. This must then be
entered in hexadecimal numbers. The first byte in the file has
address 0, the last byte has address (filesize-1).
- undo
Click this (or press ) to read the displayed chunk from the
disk into memory again. The situation is now as it was after this
chunk was last saved. This will not affect changes that have already
been saved to disk.
- top
Click this (or press ) to get the first chunk.
- ^^^ ( arrows up )
Click this (or press ) to get the previous chunk.
- vvv ( arrows down )
Click this (or press ) to get the next chunk.
- end
Click this (or press ) to get the last chunk.
- raw|txt
Click this to toggle the text only filter - useful if you are
scanning a file quickly, looking for text. If the r/w flag was on,
this will be set to r-o (for read-only) until you toggle the text
filter off again.
- r/w|r-o
Click this to lock the file to prevent accidental changes during
browsing, and click it again to unlock it. If the lock is toggled to
unlock, the text filter is automatically switched off too.
*If you attempt to change a file while r-o is in effect, this menu entry
will flash briefly to remind you.
- quit
Click this to save the current chunk and exit to the file selection
dialog page.
In ESC mode, the menu bar shows:
- ZAP 2.5, as above. Here also accessible by pressing Z.
- Help - some info about ESC mode
- UnEsc
Click this, (or press Esc, or press U) to go back to edit mode.
- Print
Click this, (or press P) to print the current chunk. If the text filter
is on, this will be used, otherwise non-printable characters will be
replaced by a hyphen ( '-' ). (Since it is very unlikely that your
printer knows the Atari graphics characters...)
- Number
Click this, (or press N) and you will be asked for a number of the
chunk to display next. This must be entered in decimal.
- Search
Click this (or press S) to enter a string to search for. Depending
on the state of ZAP, you will be asked to enter this string in HEX or
as text. You may use control characters in the text state. In HEX
state, the string must be specified as an even number of hexadecimal
digits. As a null byte is used to terminate the string you can't
search for anything following a null byte. Search is case-sensitive
and starts at the current cursor position.
- Find
Click this (or press F). The same as above, but the search will use
the previously entered string for that state.
- Chunksize
Click this, (or press C), to change the size of a chunk. The default
value, 256, is also the maximum.
- Quit
Click this, (or press Q) to exit to the file selection screen.
Besides these commands you can use the cursor keys and the mouse to
position the cursor and to switch between states. Placing the cursor
in the HEX field with the mouse will set the HEX state, placing it in
the text field will set TEXT state. , ,
and work just as in EDIT mode.
*NOTE: any action which brings a new chunk to the screen will first save
the previous chunk to disk, if the file is not locked or in text filter
mode.
The parameter section of the screen shows you things like file name,
size, cursor position, and current chunk and chunksize. If the current
chunk differs from the one on disk, the (CHANGED) flag appears after
the filename.
*NOTE: once a chunk has been written to disk, ZAP doesn't remember
whether it was modified before.
The file display field.
This consists of:
- The offset field, where the offset from the start of the file is
shown in hex.
- The hex field, which shows the byte values of the file as hexadecimal
numbers, 16 to a line.
- The ascii field, which shows the same 16 bytes of the file as the hex
field, but now as the characters in the Atari ST character set
associated with those byte values.
*NOTE: There is one exception: the NULL byte is not shown as a space,
which would be the Atari character associated with it, but as three
horizontal bars. This was done with a purpose: when editing in programs
it is very important not to overwrite terminal zeros of strings.
Therefore, these must be clearly distinguished from spaces.
*NOTE: If 'text' filter is on, only letters, digits and punctuation marks
are displayed. (A-Z | a-z | 0-9 | ; | : | . | , | ! | ?)
If you are in EDIT and r/w mode the cursor flashes.
(Except that in monochrome mode, if the cursor happens to be positioned
on a space, the flashing will be invisible)
The command/message line shows the mode ZAP is in, and this is also
where ZAP asks you to type in additional information, and where messages
appear.
*** The cursor ***
If this blinks, ZAP is in read/write mode. If it is steady, it
is not. In the latter case either the file is read-only, or the
read only option was specified, or the file was locked by you, or
the text filter is active, or ESC mode is on.
*** A short history of ZAP ***
ZAP was originally written in 1986, by D.A. Gerritsen, Medemblik, The
Netherlands. He placed the source in the public domain. The original
program was much larger and slower than the current version, as the
original author must have been, at least at that time, a beginning
C programmer. Nevertheless the program was one of the public
domain programs I regularly used, so the idea of trying to improve it
came naturally...
This task, lightly started, ended in a virtually complete rewrite.
ZAP 2.5 is now 60% of its original size and the display is much faster.
Many options were added, among which the locking facility, a better
commandline editor, the status line, the offset field, a better print
facility, a better help facility, and complete mouse support.
Every new release of ZAP is given to a few experienced computer
users to invite their comments. These are then taken into account
as far as possible.
ZAP 2.5 was written in Turbo C 1.0, using some 20, mostly small,
hand-coded assembler routines to improve size and speed. The C part of
the source (ca. 50 K) is available from me on request, the assembler
routines only in .lib form. Write to the address below.
*** Disclaimer ***
Playing with ZAP without backing up the file to be edited first is
playing with fire. To my best knowledge ZAP works exactly as
documented in this file. It has been extensively tested with correct
and incorrect input and was programmed to do the safe thing when in doubt.
However, I cannot accept responsibility for any damage which may occur
because of the use of it.
*** Who to write to ***
If you have comments on ZAP that you feel would contribute to a later
version, please do not hesitate to contact me - I shall be delighted.
Keep in mind that my goal is to keep ZAP small, safe and easy to use.
E. van Herk BBS The Dutch Connection:
Wakkerstraat 18/I (NL) 01751-13128
1097 CE Amsterdam Leave message to: Bart van Herk
The Netherlands. (9600 HST supported)
*** Update History ***
Changes to version 2.1:
- The program sometimes scrolled suddenly when a search line was
entered. This has been fixed by setting the VT-52 'no wrap' mode
before editing starts, and resetting it to 'wrap' before the program
quits.
- The program now clears the screen before quitting, as the result
when called from a commandline wasn't pretty.
Changes to version 2.2:
*Thanks to: Ernst Blok and Rob Pont for their intelligent and helpful
comments!
- The screen is no longer inverted
- Some mouse support added
- position and chunk start counting at 0 ;
- position is now displayed in decimal and hex numbering
- more elegant display algorithm
- filesize is now displayed.
- cursor management now completely under program control, to prevent
smudges when the mouse is moved over the text cursor
- The cursor blinks if the read/write mode is active.
Changes to version 2.4:
- Complete reorganization of the command structure into two menus
with fully integrated mouse interface.
- Complete rewrite of the help facility.
- New logo screen
- some streamlining of the code.
Changes to version 2.5:
- The -r flag was not recognized when ZAP was called from the desktop
as a .ttp program, because TOS capitalizes the commandstring.
ZAP now also recognizes the -R option for this.
- A few messages and texts were edited a bit for a more pleasing
screen effect.
- The program did not not always save the current chunk before quitting;
now it does.