GnuDOS library
1 Overview of the GnuDOS library
2 An example of using the GnuDOS library
3 An example of using the strings utility
4 Using the Kbd utility
5 Using the Dialogs utility
6 Using the Screen utility
7 Using the Strings utility
8 Fog: The console Form Designer
Appendix A GNU Free Documentation License
  A.1 GNU Free Documentation License
Index
GnuDOS library
**************

This manual is for the GnuDOS library (version 1.0).

1 Overview of the GnuDOS library
********************************

About the GnuDOS library
========================

GnuDOS package is a GNU software.  It is a library designed to help new
users of the GNU system, who are coming from a DOS background, fit into
the picture and start using the GNU system with ease.  It also addresses
the console programmers of such programs that have the look and feel of
old DOS system.  The library is composed of core utilities and software
applications: * The core library (corelib) contains four utilities: Kbd
(for keyboard handling), Screen (for screen drawing), Dialogs (for
dialog boxes/window drawing), and Strings (for strings functions).  *
The software applications are three: Prime (console file manager), Mino
(console text editor), and Fog (console form designer).

The rationale behind the GnuDOS corelib library
===============================================

So, you like programming under the GNU/Linux console, right?.  And you
came from the DOS land where every thing was white/blue or yellow/black.
You want to make users coming from DOS land feel home when switching to
the powerful GNU system.  Okay, That's good.  But there are some catches
when programming under the console.  First of all, you can't format your
output exactly the way you want in terms of color, positioning, and so
on.  You can go deep and use terminal escape sequences (as most
GNU/Linux consoles emulate the VT100 terminal), but who can remember
these?.

   Next comes the problem of the terminal driver interfering with the
keyboard input.  You don't get the real key scancodes sent by the
keyboard.  The driver gets in the way and performs a lot of steps to map
the right key to the right keycode, process some special key
combinations (like CTRL+ALT+DEL) and so on, before passing the result to
the terminal.  And in the case of XTerminal, the X terminal does more
processing before sending the final result to your program.  You say
what difference does it make?  you are taking all the pain off my head,
why should I bother?  Here is why:

   If you want your program to be REALLY interactive, like waiting the
user to press a key (press, not press and release and press ENTER!) you
can't rely on the good old getc() or getchar() functions, as they will
return an input char alright, but only after the user presses ENTER!.
That's no good for us, you know.  Another thing is reading special keys,
like SHIFT, ALT and CTRL. You don't get scancodes for these keys (not
all times, at least).

   So how to make your program get over these problems?  well, you can
implement your own keyboard driver, which will be very painful to
construct your keymap tables and do all the calculations, or your can
interfere with the input sent from the console driver before it does any
further processing on it.  The console-utils *Note Kbd::.  utility does
this.  It tells the console driver to send it raw data (with no
processing), and it then looks into its own table to see what key (or
key combinations) does this scancode means, and then gives you the
result.

   Right now, the *Note Kbd::.  utility doesn't recognize ALL the
possible keys that can be entered through a keyboard.  It recognizes all
the alphanumeric charset, the TAB, CAPS, ENTER, SPACE, CTRL, ALT, SHIFT,
DEL, INS, HOME, ESC, and END. More keys (like function keys F1-F12) will
be added with future releases.

   The other thing the GnuDOS library provides is a utility for
controlling the screen *Note Screen::.  It provides functions for
getting the screen size (height and width), setting the screen colors,
and clearing the screen.

   The third utility is the *Note Dialogs::.  utility, which (as its
name says) provides a ready to use class of dialog boxes under the
console.  It provides two types of boxes: simple dialog box (to provide
the user with a messeage, or asking for confirmation, ...)  and an input
box (to ask the user to enter some input).

   The fourth utility is the *Note Strings::.  utility.  It provides
some handy functions to make working with strings under C much easier
for the programmer.

   There are two sample programs: the *Note hello_gnudos::.
demonstrates how to use the various elements and utilities of the
console-utils (GnuDOS) library (except for the strings utility).  The
other example is *Note hello_strings::.  which demonstrates how to use
the strings utility.

2 An example of using the GnuDOS library
****************************************

This is a sample program that demonstrates how to use the GnuDOS library
utilities:

     #include "console/dialogs.h"
     #include "console/screen.h"
     #include "console/kbd.h"

     void sighandler(int signo) {
         //do what ever needs to be done here. The following line is just an example.
         fprintf(stderr, "SIGNAL %d received\n", signo);
     }

     int main(int argc, char *argv[]) {
       if(!catchSignals()) {
         fprintf(stderr, "Error catching signals. Exiting.\n");
         exit(1);
       }
       if(!init_kbd()) {
         fprintf(stderr, "Error initializing keyboard. Aborting.\n");
         exit(1);
       }

       getScreenSize();		//gets screen size
       clearScreenC(WHITE, BGBLACK);	//clear the screen
       //loads color arrays with default values
       loadDefaultColors();
       setScreenColors(FG_COLOR[COLOR_WINDOW], BG_COLOR[COLOR_WINDOW]);

       msgBox("This was an example", OK, INFO);
       drawBox(2, 2, SCREEN_H-2, SCREEN_W-2, " Example ", YES);
       locate(3, 3); printf("Hello GnuDOS!");
       locate(4, 3); printf("This is an example Window.");
       locate(5, 3); printf("Press ENTER to exit...");
       while(1) {
         if(getKey() == ENTER_KEY) break;
       }

       clearScreen();
       //very important to restore keyboard state to its
       //previous state before exiting
       restore_kbd();
       exit(0);
     }

   Note that including the header file "dialogs.h" automatically
includes both "screen.h" and "kbd.h" as the dialogs utility uses both of
the other two.

   And now REMEMBER two things: (1) a call to initTerminal() must be
invoked before using the library (2) a call restoreTerminal() must be
done before exiting the program For deatils about these functions please
see *Note Kbd::.

   If you forget point (2), you will leave the user's terminal in raw
mode, which (under console) means he/she will not be able to do
virtually anything (not even switching terminal by CTRL+ALT+F key!).
The only way out is a reboot!.  Under X it is less worse, usually the
user will need to close the xterm or kill the process.  Still though, it
is IMPERATIVE to call restoreTerminal() before exiting your program!.
To make sure no funny things happen (like your progrm crashing for
whatever reason, or your admin killing it, to name a few) before you
call restoreTerminal(), you better use the catchSignals() function of
the *Note Dialogs::.  utility.  Remember though that there are some
signals that can't be caught by your program, like the SIGSTOP and
SIGKILL signals.  This is why we used the catchSignals() function
instead of the catchAllSignals() function.

3 An example of using the strings utility
*****************************************

This is a sample program that demonstrates how to use the strings
utility:

     #include <stdio.h>
     #include "strings.h"

     int main(int argc, char **argv) {
         printf("Hello World");
         str s;
         s = "Hello world";
         printf("\n%s", s);
         printf("\n%d", indexof(s, 'H'));
         printf("\n%d", nindexof('H'));
         printf("\n%d", lindexof(s, 'H'));
         printf("\n%s", substr(s, 4));
         printf("\n%s", nsubstr(s, 4, 5));
         return 0;
     }

4 Using the Kbd utility
***********************

The Kbd utility of the GnuDOS library provides functions for getting
input from the keyboard, initializing and restoring the terminal state
to enable the utility to grasp proper keyboard input, and some global
variables.

   The global variables defined in kbd.h are:

     bool ALT;
     bool CTRL;
     bool SHIFT;
     bool CAPS;
     bool INSERT;
     bool X_IS_RUNNING;

   This is their explanation:
 ALT: Boolean variable that indicates the state of the ALT key
  (1=pressed, 0=released)
 CTRL: Boolean variable that indicates the state of the CTRL key
  (1=pressed, 0=released)
 SHIFT: Boolean variable that indicates the state of the SHIFT key
  (1=pressed, 0=released)
 CAPS: Boolean variable that indicates the state of CAPSLOCK
  (1=pressed/ON, 0=released/OFF)
 INSERT: Boolean variable that indicates the state of the INSERT key
  (1=pressed/ON, 0=released/OFF)
 X_IS_RUNNING: Boolean variable that indicates whether X is running
  (1=running under X, 0=running under console)

   Three functions are defined:

     int initTerminal();
     void restoreTerminal();
     int getKey();

   The initTerminal() function must be called before any other library
function is used.  It initializes the terminal for library use.  What
this means in simple English is that the console will be messed up for
other programs during your program execution.  This is why it is
MANDATORY to call restoreTerminal() just before your program exits to
ensure that the terminal is restored to its previous state.  Failing to
do so, the terminal is left in an intermediate state that the user will
have only one option: to reboot (under console) or to kill (or close)
the terminal (under X).

   The function getKey() is called to get the next key press from the
keyboard.  It actually relies on two functions internally: one to get
the key under X, the other to get it under console mode.  The difference
between the two is of no relevance to the user.  Just call getKey() to
get the next keypress whether under X or not.

   The getKey() function returns its result as an integer.  For
alphanumeric keys this will mean the ASCII value of that key (ASCII
65-90 for Latin capitals, 97-122 for Latin smalls, 32 for Space, 33-64
for numbers and punctuation, 96 for backtick, 123-126 for braces,
vertical bar and tilde).  Other keys like arrows and ESC and ENTER are
defined as macros in the kbd.h file:

     #define ESC_KEY		27
     #define BACKSPACE_KEY	8
     #define TAB_KEY		9
     #define ENTER_KEY	13
     #define CAPS_KEY	1
     #define SHIFT_KEY	2
     #define CTRL_KEY	3
     #define ALT_KEY		4
     #define SPACE_KEY	32
     #define UP_KEY		5
     #define DOWN_KEY	6
     #define LEFT_KEY	7
     #define RIGHT_KEY	10
     #define DEL_KEY		11
     #define	HOME_KEY	12
     #define END_KEY		14
     #define INS_KEY		15
     #define SHIFT_DOWN	17
     #define SHIFT_UP	18
     #define PGUP_KEY	19
     #define PGDOWN_KEY	20

   What you need to do is to match the return value of getKey() against
the desired key.  For example:

     if(getKey() == ESC_KEY)
        exit(0);

   Or, more elegantly, in a switch loop:

     int c = getKey();
     switch(c) {
       case(ESC_KEY):
          //do-something
          break;
       case(UP_KEY):
          //do-other-stuff
          break;
       default:
          if(c >= 32 && c <= 126)
             print("%c", c);
          break;
     }

   To test for special key combinations (e.g.  CTRL+S):

     c = getKey()
     if(c == 's' && CTRL) {
        //do something
     }

5 Using the Dialogs utility
***************************

The Dialogs utility provides three types of dialog boxes: simple dialog
boxes, input boxes, and empty boxes.

Simple Dialog Box
=================

The function to draw a simple dialog box is defined in "dialogs.h" as:

     int msgBox(char *msg, int buttons, msgtype tmsg);

   Where:
   * msg: is a pointer to the string that will be the output message of
     the dialog box
   * buttons: an integer value defining the number and type of buttons
     to be displayed (see below)
   * tmsg: a value of type "msgtype" (see below) defining the type of
     dialog box.  This will be the title of the dialog

   The value of 'buttons' can be: OK, OK|CANCEL, or YES|NO. Note when
using two buttons they need to be ORed with the vertical bar.  The
macros defining those buttons are declared in "dialogs.h" as:

     //buttons used in message boxes//
     #define OK	1	//00000001
     #define YES	2	//00000010
     #define CANCEL	4	//00000100
     #define NO	8	//00001000

   The value of 'tsmg' can be:
   - INFO: This is an information box.  The title will be "INFORMATION"
   - ERROR: This is an error message box.  The title will be "ERROR"
   - CONFIRM: This is a confirmation dialog box.  The title will be
     "CONFIRMATION"

Input boxes
===========

The function to draw a simple dialog box is defined in "dialogs.h" as:

     char* inputBox(char *msg, char *title);

   Where:
   * msg: is a pointer to the string that will be the output message of
     the dialog box
   * title: is a pointer to the string that will be the title of the
     input box

   The function returns the user input as a char pointer.  If the user
entered nothing, or pressed CANCEL button or ESC, the function returns
NULL. You can also access the return value in the globally accessed
variable 'input', which is defined:

     char input[MAX_INPUT_MSG_LEN+1];	//input string returned by inputBox() function

   Another function for drawing input boxes is defined:

     char* inputBoxI(char *msg, char *inputValue, char *title);

   The only difference is that it takes as the second parameter a string
that will be displayed in the input box as an initial input value for
the user.  This is helpful if you want to give the user a default value
for whatever input is required from the user.  The user can change the
input or just press ENTER and accept the default value.

Empty boxes
===========

Drawing empty boxes or windows is done via one of two functions:

     void drawBox(int x1, int y1, int x2, int y2, char *title, int clearArea);
     void drawBoxP(point p1, point p2, char *title, int clearArea);

   They basically do the same thing, except that drawBoxP() accepts the
window coordinates as two 'point' structures which are defined as:

     typedef struct { int row; int col; } point;

   Whereas the drawBox() function accepts coordinates as four integer
values.  The explanation of the parameters to the two functions is as
follows:
   * x1: The x-coordinate (row) of the upper left corner
   * y1: The y-coordinate (column) of the upper left corner
   * x2: The x-coordinate (row) of the lower right corner
   * y2: The y-coordinate (column) of the lower right corner
   * char *title: A string pointer to the title of the dialog box
   * int clearArea: A boolean value indicating whether to clear the box
     area (YES=clear, NO=don't clear).  Not clearing the box area can be
     handy when, for example, you need to redraw the window frame but
     leave the window contents intact.

   Other things of concern are:

     int MAX_MSG_BOX_W;
     int MAX_MSG_BOX_H;
     #define MAX_INPUT_MSG_LEN 100

   The first two are global variables used to determine the maximum size
of a dialog box.  MAX_MSG_BOX_W defines the maximum width (columns) and
MAX_MSG_BOX_H the maxium height (rows).  Their values are calculated in
the msgBox() and inputBox() functions as:

     MAX_MSG_BOX_W = SCREEN_W-2;
     MAX_MSG_BOX_H = SCREEN_H-2;

   The last one, MAX_INPUT_MSG_LEN is a macro defining the maximum
length of the input string returned by an input box.  Currently it is
restricted to 100 chars.

The catchSignals() function
===========================

The last two functions of "dialogs.h" are:

     int catchSignals();
     int catchAllSignals();

   Which are handy and so important.  Remember that after a call to
initTerminal() the terminal will be in an intermediate state, which is
not of much use to the user.  Calling restoreTerminal() is an important
step to do before leaving your program.  But what if your program
crashed for whatever reason?  (bad things happen all the time), or if a
system administrator decided to kill your process?.  Here is what
catchSignals() does: it catches all the important signals (namely:
SIGINT, SIGQUIT, SIGABRT, and SIGTERM) and passes them to a signal
handler, which you will define as:

     void sighandler(int signo)
     {
         //do what ever needs to be done here. The following line is just an example.
         fprintf(stderr, "SIGNAL %d received\n", signo);
     }

   The catchAllSignals() does the same, except it tries to catch also
SIGSTP, SIGKILL, and SIGSTOP. It is a futile effort of course, as these
signals can't be caught, it is just included for convenience.
If either function succeeds in catching the signals, it will return 1.
Otherwise, 0.  Expect catchAllSignals() to return 0 at all times because
of the reason above.
Note that you will need to define the signal handler even if you will
not use the catchSignals() function (which is, by the way, not
recommended at all!  We explained the reasons several times above).  It
can be defined as an empty function as:

     void sighandler(int signo)
     {
     }

   Again, please define the signal handler in a proper way whenever
possible.

6 Using the Screen utility
**************************

The screen utility provides functions to manipulate the screen colors,
clearing the screen, and positioning of the cursor.  It also defines
values for the screen size.  The member variables of the screen utility
(defined in screen.h) are:

      int SCREEN_W;
      int SCREEN_H;

   Both these variables are filled with values after a call to
getScreenSize().

      int FG_COLOR[color_components];
      int BG_COLOR[color_components];

   The color_components is a macro defined with a value of 4.  The
possible values for color_components which is an index into arrays of
colors determining what color is assigned to which component (i.e.,
dialogs, buttons, ...)  are:

      COLOR_WINDOW		0
      COLOR_HIGHLIGHT_TEXT	1
      COLOR_BUTTONS	 	2
      COLOR_HBUTTONS		3

   You can define the colors in the color arrays by using integer
values, although using macro names (as discussed below) is recommended.
Initializing the arrays can be done with code like:

       FG_COLOR[COLOR_WINDOW] = 37;
       FG_COLOR[COLOR_HIGHLIGHT_TEXT] = 34;
       FG_COLOR[COLOR_MENU_BAR] = 34;
       FG_COLOR[COLOR_STATUS_BAR] = 34;
       FG_COLOR[COLOR_BUTTONS] = 37;
       FG_COLOR[COLOR_HBUTTONS] = 32;
       BG_COLOR[COLOR_WINDOW] = 44;
       BG_COLOR[COLOR_HIGHLIGHT_TEXT] = 47;
       BG_COLOR[COLOR_MENU_BAR] = 47;
       BG_COLOR[COLOR_STATUS_BAR] = 47;
       BG_COLOR[COLOR_BUTTONS] = 41;
       BG_COLOR[COLOR_HBUTTONS] = 41;

   For convenience, the names of colors used in screen utility functions
can be retrieved from the array screen_colors[] after a call to
getScreenColors():

      getScreenColors();
      for(int i = 0; i < 16; i++)
        printf("%s\n", screen_colors[i]);

   To set the screen colors (e.g.  before clearing the screen,), use the
function:

      void setScreenColors(int FG, int BG);

   where FG is the foreground color, BG is the background color.  Color
values are defined as macros in the (screen.h) file:

      #define BLACK      30      //set black foreground
      #define RED        31      //set red foreground
      #define GREEN      32      //set green foreground
      #define BROWN      33      //set brown foreground
      #define BLUE       34      //set blue foreground
      #define MAGENTA    35      //set magenta foreground
      #define CYAN       36      //set cyan foreground
      #define WHITE      37      //set white foreground
      #define BGBLACK    40      //set black background
      #define BGRED      41      //set red background
      #define BGGREEN    42      //set green background
      #define BGBROWN    43      //set brown background
      #define BGBLUE     44      //set blue background
      #define BGMAGENTA  45      //set magenta background
      #define BGCYAN     46      //set cyan background
      #define BGWHITE    47      //set white background
      #define BGDEFAULT  49      //set default background color

   To get the size of screen coordinates, use function:

      void getScreenSize();

   which will fill the values into SCREEN_W and SCREEN_H global
variables.
The functions

      void clearScreen();
      void clearScreenC(int FG, int BG);

   basically do the same thing, except clearScreen() uses whatever
colors where passed into previous call of setScreenColors(), and
clearScreenC() takes the values of colors to use when clearing the
screen.  Last color function is

      void loadDefaultColors();

   which resets the color arrays into default values.
To reposition the cursor, use:

      void locate(int row, int col);

   giving the row and column as int values.  Remember the screen has
top-left based coordinates, meaning position 1-1 is at the top-left
corner, position 25-80 is at the bottom-right (for a 25x80 screen size).

7 Using the Strings utility
***************************

The strings utility defines some handy functions for dealing with
strings.  Strings in C are problematic: they involve a lot of pointer
manipulation which is often complicated, error-prone and a source of
bugs.  The strings utility defines a wrapper type for strings (only for
convenience), which is defined as:

     typedef char *str;

   The functions of the strings utility, as defined in "strings.h", are:

     int indexof(str string, char chr);
     int nindexof(char chr);
     int lindexof(str string, char chr);

     str substr(str string, int start);
     str nsubstr(str string, int start, int length);
     str ltrim(str string);
     str rtrim(str string);
     str trim(str string);

     str toupper(str string);
     str tolower(str string);

   What the functions do is as following:
   * The indexof() function returns the zero-based index of the first
     occurence of 'chr' in 'string'.
   * The nindexof() function returns the zero-based index of the next
     occurence of 'chr' in 'string'.  It should be called after a
     previous call the indexof().
   * The lindexof() function returns the zero-based index of the last
     occurence of 'chr' in 'string'.  If there is only one occurence of
     'chr' in 'string', the return value is essentially the same as that
     of indexof().
   * The substr() function returns a substring of 'string' starting from
     position 'start'.  Note start is zero-based.
   * The nsubstr() function returns a substring of 'string' starting
     from position 'start' and spanning 'length' characters.  Note start
     is zero-based.
   * The ltrim() function trims (removes) all the whitespace characters
     from the strings' left side.  Whitespace characters removed are:
     space, tab, and newline.  If there are no whitespace characters in
     the lefthand side of the string, the original string is returned.
   * The rtrim() function trims (removes) all the whitespace characters
     from the strings' right side.  Whitespace characters removed are:
     space, tab, and newline.  If there are no whitespace characters in
     the lefthand side of the string, the original string is returned.
   * The trim() function trims (removes) all the whitespace characters
     from both strings' ends.  Whitespace characters removed are: space,
     tab, and newline.  If there are no whitespace characters in either
     side of the string, the original string is returned.
   * The toupper() function returns the string in upper case letters.
   * The tolower() function returns the string in lower case letters.

8 Fog: The console Form Designer
********************************

Using the utilities of the GnuDOS library will ease the life of console
programmers very much, but still though, putting it all together to
design a complete user interface (or a form) can be a tedious job.  The
FOG (Form Designer) helps with this aspect of programming.  It provides
a development environment that will make it easy to design an
application interface for a program using the console-utils library
under the console.

   Fog is installed as part of the GnuDOS library package.  It can be
invoked by running:

     $ fog

   from the command line.  The user interface is very simple:
   * Toolbox: Contains the set of 'tools' that can be added to a form,
     such as option items and bulleted items
   * Form design: Displays the form under design
   * Menu bar: Contains the menus File, Edit and Help

   Fog saves the form design typically in the same working directory
from which it was invoked.  This can be changed by specifying another
path and file name in the Save dialog box.  Fog design files have the
extension '.fog', to be distinct from other programs' files.  These
files should not be edited by hand.  Instead, open Fog and edit the form
design and re-save the form.  After finishing the form design, Fog can
create a skeleton project that has most components pre-written for the
programmer, mainly the parts that deal with the user interface and
getting input from the user.

   Select 'Write Project' from the File menu, or just press CTRL+W. Fog
will write three files in the same project directory:
   * main.c: Contains the main() program function.  If the form contains
     any buttons, it will contain a function event handler which is
     called whenever a button is clicked (or the user presses ENTER on
     it).
   * fog_header.h: Contains global variable declarations and function
     prototypes.
   * form_design.c: Contains the following function definitions:
        - void init_form(): Initializes the form and fills global
          variables
        - void refresh_form(): Redraws the form into the screen
        - void input_loop(): Catches user input on the form
        - void close_form(): Restores the terminal and clears the screen
          before exiting

   A program designed with Fog can be compiled as following (if using
gcc compiler):

     $ gcc -o myprog main.c form_design.c -lGnuDOS

Appendix A GNU Free Documentation License
*****************************************

A.1 GNU Free Documentation License
==================================

                      Version 1.2, November 2002

     Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
     51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA

     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

  0. PREAMBLE

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     functional and useful document "free" in the sense of freedom: to
     assure everyone the effective freedom to copy and redistribute it,
     with or without modifying it, either commercially or
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     being considered responsible for modifications made by others.

     This License is a kind of "copyleft", which means that derivative
     works of the document must themselves be free in the same sense.
     It complements the GNU General Public License, which is a copyleft
     license designed for free software.

     We have designed this License in order to use it for manuals for
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  1. APPLICABILITY AND DEFINITIONS

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     A "Modified Version" of the Document means any work containing the
     Document or a portion of it, either copied verbatim, or with
     modifications and/or translated into another language.

     A "Secondary Section" is a named appendix or a front-matter section
     of the Document that deals exclusively with the relationship of the
     publishers or authors of the Document to the Document's overall
     subject (or to related matters) and contains nothing that could
     fall directly within that overall subject.  (Thus, if the Document
     is in part a textbook of mathematics, a Secondary Section may not
     explain any mathematics.)  The relationship could be a matter of
     historical connection with the subject or with related matters, or
     of legal, commercial, philosophical, ethical or political position
     regarding them.

     The "Invariant Sections" are certain Secondary Sections whose
     titles are designated, as being those of Invariant Sections, in the
     notice that says that the Document is released under this License.
     If a section does not fit the above definition of Secondary then it
     is not allowed to be designated as Invariant.  The Document may
     contain zero Invariant Sections.  If the Document does not identify
     any Invariant Sections then there are none.

     The "Cover Texts" are certain short passages of text that are
     listed, as Front-Cover Texts or Back-Cover Texts, in the notice
     that says that the Document is released under this License.  A
     Front-Cover Text may be at most 5 words, and a Back-Cover Text may
     be at most 25 words.

     A "Transparent" copy of the Document means a machine-readable copy,
     represented in a format whose specification is available to the
     general public, that is suitable for revising the document
     straightforwardly with generic text editors or (for images composed
     of pixels) generic paint programs or (for drawings) some widely
     available drawing editor, and that is suitable for input to text
     formatters or for automatic translation to a variety of formats
     suitable for input to text formatters.  A copy made in an otherwise
     Transparent file format whose markup, or absence of markup, has
     been arranged to thwart or discourage subsequent modification by
     readers is not Transparent.  An image format is not Transparent if
     used for any substantial amount of text.  A copy that is not
     "Transparent" is called "Opaque".

     Examples of suitable formats for Transparent copies include plain
     ASCII without markup, Texinfo input format, LaTeX input format,
     SGML or XML using a publicly available DTD, and standard-conforming
     simple HTML, PostScript or PDF designed for human modification.
     Examples of transparent image formats include PNG, XCF and JPG.
     Opaque formats include proprietary formats that can be read and
     edited only by proprietary word processors, SGML or XML for which
     the DTD and/or processing tools are not generally available, and
     the machine-generated HTML, PostScript or PDF produced by some word
     processors for output purposes only.

     The "Title Page" means, for a printed book, the title page itself,
     plus such following pages as are needed to hold, legibly, the
     material this License requires to appear in the title page.  For
     works in formats which do not have any title page as such, "Title
     Page" means the text near the most prominent appearance of the
     work's title, preceding the beginning of the body of the text.

     A section "Entitled XYZ" means a named subunit of the Document
     whose title either is precisely XYZ or contains XYZ in parentheses
     following text that translates XYZ in another language.  (Here XYZ
     stands for a specific section name mentioned below, such as
     "Acknowledgements", "Dedications", "Endorsements", or "History".)
     To "Preserve the Title" of such a section when you modify the
     Document means that it remains a section "Entitled XYZ" according
     to this definition.

     The Document may include Warranty Disclaimers next to the notice
     which states that this License applies to the Document.  These
     Warranty Disclaimers are considered to be included by reference in
     this License, but only as regards disclaiming warranties: any other
     implication that these Warranty Disclaimers may have is void and
     has no effect on the meaning of this License.

  2. VERBATIM COPYING

     You may copy and distribute the Document in any medium, either
     commercially or noncommercially, provided that this License, the
     copyright notices, and the license notice saying this License
     applies to the Document are reproduced in all copies, and that you
     add no other conditions whatsoever to those of this License.  You
     may not use technical measures to obstruct or control the reading
     or further copying of the copies you make or distribute.  However,
     you may accept compensation in exchange for copies.  If you
     distribute a large enough number of copies you must also follow the
     conditions in section 3.

     You may also lend copies, under the same conditions stated above,
     and you may publicly display copies.

  3. COPYING IN QUANTITY

     If you publish printed copies (or copies in media that commonly
     have printed covers) of the Document, numbering more than 100, and
     the Document's license notice requires Cover Texts, you must
     enclose the copies in covers that carry, clearly and legibly, all
     these Cover Texts: Front-Cover Texts on the front cover, and
     Back-Cover Texts on the back cover.  Both covers must also clearly
     and legibly identify you as the publisher of these copies.  The
     front cover must present the full title with all words of the title
     equally prominent and visible.  You may add other material on the
     covers in addition.  Copying with changes limited to the covers, as
     long as they preserve the title of the Document and satisfy these
     conditions, can be treated as verbatim copying in other respects.

     If the required texts for either cover are too voluminous to fit
     legibly, you should put the first ones listed (as many as fit
     reasonably) on the actual cover, and continue the rest onto
     adjacent pages.

     If you publish or distribute Opaque copies of the Document
     numbering more than 100, you must either include a machine-readable
     Transparent copy along with each Opaque copy, or state in or with
     each Opaque copy a computer-network location from which the general
     network-using public has access to download using public-standard
     network protocols a complete Transparent copy of the Document, free
     of added material.  If you use the latter option, you must take
     reasonably prudent steps, when you begin distribution of Opaque
     copies in quantity, to ensure that this Transparent copy will
     remain thus accessible at the stated location until at least one
     year after the last time you distribute an Opaque copy (directly or
     through your agents or retailers) of that edition to the public.

     It is requested, but not required, that you contact the authors of
     the Document well before redistributing any large number of copies,
     to give them a chance to provide you with an updated version of the
     Document.

  4. MODIFICATIONS

     You may copy and distribute a Modified Version of the Document
     under the conditions of sections 2 and 3 above, provided that you
     release the Modified Version under precisely this License, with the
     Modified Version filling the role of the Document, thus licensing
     distribution and modification of the Modified Version to whoever
     possesses a copy of it.  In addition, you must do these things in
     the Modified Version:

       A. Use in the Title Page (and on the covers, if any) a title
          distinct from that of the Document, and from those of previous
          versions (which should, if there were any, be listed in the
          History section of the Document).  You may use the same title
          as a previous version if the original publisher of that
          version gives permission.

       B. List on the Title Page, as authors, one or more persons or
          entities responsible for authorship of the modifications in
          the Modified Version, together with at least five of the
          principal authors of the Document (all of its principal
          authors, if it has fewer than five), unless they release you
          from this requirement.

       C. State on the Title page the name of the publisher of the
          Modified Version, as the publisher.

       D. Preserve all the copyright notices of the Document.

       E. Add an appropriate copyright notice for your modifications
          adjacent to the other copyright notices.

       F. Include, immediately after the copyright notices, a license
          notice giving the public permission to use the Modified
          Version under the terms of this License, in the form shown in
          the Addendum below.

       G. Preserve in that license notice the full lists of Invariant
          Sections and required Cover Texts given in the Document's
          license notice.

       H. Include an unaltered copy of this License.

       I. Preserve the section Entitled "History", Preserve its Title,
          and add to it an item stating at least the title, year, new
          authors, and publisher of the Modified Version as given on the
          Title Page.  If there is no section Entitled "History" in the
          Document, create one stating the title, year, authors, and
          publisher of the Document as given on its Title Page, then add
          an item describing the Modified Version as stated in the
          previous sentence.

       J. Preserve the network location, if any, given in the Document
          for public access to a Transparent copy of the Document, and
          likewise the network locations given in the Document for
          previous versions it was based on.  These may be placed in the
          "History" section.  You may omit a network location for a work
          that was published at least four years before the Document
          itself, or if the original publisher of the version it refers
          to gives permission.

       K. For any section Entitled "Acknowledgements" or "Dedications",
          Preserve the Title of the section, and preserve in the section
          all the substance and tone of each of the contributor
          acknowledgements and/or dedications given therein.

       L. Preserve all the Invariant Sections of the Document, unaltered
          in their text and in their titles.  Section numbers or the
          equivalent are not considered part of the section titles.

       M. Delete any section Entitled "Endorsements".  Such a section
          may not be included in the Modified Version.

       N. Do not retitle any existing section to be Entitled
          "Endorsements" or to conflict in title with any Invariant
          Section.

       O. Preserve any Warranty Disclaimers.

     If the Modified Version includes new front-matter sections or
     appendices that qualify as Secondary Sections and contain no
     material copied from the Document, you may at your option designate
     some or all of these sections as invariant.  To do this, add their
     titles to the list of Invariant Sections in the Modified Version's
     license notice.  These titles must be distinct from any other
     section titles.

     You may add a section Entitled "Endorsements", provided it contains
     nothing but endorsements of your Modified Version by various
     parties--for example, statements of peer review or that the text
     has been approved by an organization as the authoritative
     definition of a standard.

     You may add a passage of up to five words as a Front-Cover Text,
     and a passage of up to 25 words as a Back-Cover Text, to the end of
     the list of Cover Texts in the Modified Version.  Only one passage
     of Front-Cover Text and one of Back-Cover Text may be added by (or
     through arrangements made by) any one entity.  If the Document
     already includes a cover text for the same cover, previously added
     by you or by arrangement made by the same entity you are acting on
     behalf of, you may not add another; but you may replace the old
     one, on explicit permission from the previous publisher that added
     the old one.

     The author(s) and publisher(s) of the Document do not by this
     License give permission to use their names for publicity for or to
     assert or imply endorsement of any Modified Version.

  5. COMBINING DOCUMENTS

     You may combine the Document with other documents released under
     this License, under the terms defined in section 4 above for
     modified versions, provided that you include in the combination all
     of the Invariant Sections of all of the original documents,
     unmodified, and list them all as Invariant Sections of your
     combined work in its license notice, and that you preserve all
     their Warranty Disclaimers.

     The combined work need only contain one copy of this License, and
     multiple identical Invariant Sections may be replaced with a single
     copy.  If there are multiple Invariant Sections with the same name
     but different contents, make the title of each such section unique
     by adding at the end of it, in parentheses, the name of the
     original author or publisher of that section if known, or else a
     unique number.  Make the same adjustment to the section titles in
     the list of Invariant Sections in the license notice of the
     combined work.

     In the combination, you must combine any sections Entitled
     "History" in the various original documents, forming one section
     Entitled "History"; likewise combine any sections Entitled
     "Acknowledgements", and any sections Entitled "Dedications".  You
     must delete all sections Entitled "Endorsements."

  6. COLLECTIONS OF DOCUMENTS

     You may make a collection consisting of the Document and other
     documents released under this License, and replace the individual
     copies of this License in the various documents with a single copy
     that is included in the collection, provided that you follow the
     rules of this License for verbatim copying of each of the documents
     in all other respects.

     You may extract a single document from such a collection, and
     distribute it individually under this License, provided you insert
     a copy of this License into the extracted document, and follow this
     License in all other respects regarding verbatim copying of that
     document.

  7. AGGREGATION WITH INDEPENDENT WORKS

     A compilation of the Document or its derivatives with other
     separate and independent documents or works, in or on a volume of a
     storage or distribution medium, is called an "aggregate" if the
     copyright resulting from the compilation is not used to limit the
     legal rights of the compilation's users beyond what the individual
     works permit.  When the Document is included in an aggregate, this
     License does not apply to the other works in the aggregate which
     are not themselves derivative works of the Document.

     If the Cover Text requirement of section 3 is applicable to these
     copies of the Document, then if the Document is less than one half
     of the entire aggregate, the Document's Cover Texts may be placed
     on covers that bracket the Document within the aggregate, or the
     electronic equivalent of covers if the Document is in electronic
     form.  Otherwise they must appear on printed covers that bracket
     the whole aggregate.

  8. TRANSLATION

     Translation is considered a kind of modification, so you may
     distribute translations of the Document under the terms of section
     4.  Replacing Invariant Sections with translations requires special
     permission from their copyright holders, but you may include
     translations of some or all Invariant Sections in addition to the
     original versions of these Invariant Sections.  You may include a
     translation of this License, and all the license notices in the
     Document, and any Warranty Disclaimers, provided that you also
     include the original English version of this License and the
     original versions of those notices and disclaimers.  In case of a
     disagreement between the translation and the original version of
     this License or a notice or disclaimer, the original version will
     prevail.

     If a section in the Document is Entitled "Acknowledgements",
     "Dedications", or "History", the requirement (section 4) to
     Preserve its Title (section 1) will typically require changing the
     actual title.

  9. TERMINATION

     You may not copy, modify, sublicense, or distribute the Document
     except as expressly provided for under this License.  Any other
     attempt to copy, modify, sublicense or distribute the Document is
     void, and will automatically terminate your rights under this
     License.  However, parties who have received copies, or rights,
     from you under this License will not have their licenses terminated
     so long as such parties remain in full compliance.

  10. FUTURE REVISIONS OF THIS LICENSE

     The Free Software Foundation may publish new, revised versions of
     the GNU Free Documentation License from time to time.  Such new
     versions will be similar in spirit to the present version, but may
     differ in detail to address new problems or concerns.  See
     <http://www.gnu.org/copyleft/>.

     Each version of the License is given a distinguishing version
     number.  If the Document specifies that a particular numbered
     version of this License "or any later version" applies to it, you
     have the option of following the terms and conditions either of
     that specified version or of any later version that has been
     published (not as a draft) by the Free Software Foundation.  If the
     Document does not specify a version number of this License, you may
     choose any version ever published (not as a draft) by the Free
     Software Foundation.

ADDENDUM: How to use this License for your documents
====================================================

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

       Copyright (C)  YEAR  YOUR NAME.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.2
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

   If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts."  line with this:

         with the Invariant Sections being LIST THEIR TITLES, with
         the Front-Cover Texts being LIST, and with the Back-Cover Texts
         being LIST.

   If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

   If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit
their use in free software.

Index
*****

* Menu:

* Button values in dialog boxes:         Dialogs.             (line 330)
* Color arrays:                          Screen.              (line 472)
* Color components:                      Screen.              (line 480)
* Color definitions:                     Screen.              (line 518)
* Dialogs:                               Dialogs.             (line 305)
* Empty Boxes:                           Dialogs.             (line 372)
* Example of defining the Color arrays:  Screen.              (line 489)
* FDL, GNU Free Documentation License:   GNU Free Documentation License.
                                                              (line 678)
* Fog:                                   Fog.                 (line 619)
* Global Dialog Box variables:           Dialogs.             (line 398)
* Global Kbd variables:                  Kbd.                 (line 202)
* Global keyboard variables:             Kbd.                 (line 202)
* GnuDOS library overview:               Overview.            (line  16)
* hello_gnudos:                          hello_gnudos.        (line 101)
* hello_strings:                         hello_strings.       (line 171)
* Input Boxes:                           Dialogs.             (line 342)
* Input Boxes with default input values: Dialogs.             (line 362)
* Kbd:                                   Kbd.                 (line 194)
* Kbd functions:                         Kbd.                 (line 225)
* Keyboard functions:                    Kbd.                 (line 225)
* Overview:                              Overview.            (line  17)
* Sample of using the getKey() function: Kbd.                 (line 284)
* Screen:                                Screen.              (line 458)
* Simple Dialog Boxes:                   Dialogs.             (line 311)
* Special keys:                          Kbd.                 (line 254)
* Strings:                               Strings.             (line 563)
* The catchSignals() function:           Dialogs.             (line 416)
* The clearScreen() function:            Screen.              (line 544)
* The clearScreenC() function:           Screen.              (line 544)
* The console Form Designer:             Fog.                 (line 619)
* The Dialogs utility:                   Dialogs.             (line 305)
* The getScreenColors() function:        Screen.              (line 506)
* The getScreenSize() function:          Screen.              (line 538)
* The indexof() function:                Strings.             (line 590)
* The Kbd utility:                       Kbd.                 (line 194)
* The lindexof() function:               Strings.             (line 594)
* The loadDefaultColors() function:      Screen.              (line 552)
* The locate() function:                 Screen.              (line 557)
* The ltrim() function:                  Strings.             (line 603)
* The nindexof() function:               Strings.             (line 591)
* The nsubstr() function:                Strings.             (line 600)
* The rtrim() function:                  Strings.             (line 607)
* The Screen utility:                    Screen.              (line 458)
* The setScreenColors() function:        Screen.              (line 513)
* The sighandler() function:             Dialogs.             (line 434)
* The Str typedef:                       Strings.             (line 572)
* The Strings utility:                   Strings.             (line 563)
* The Strings utility function definitions: Strings.          (line 576)
* The substr() function:                 Strings.             (line 598)
* The tolower() function:                Strings.             (line 616)
* The toupper() function:                Strings.             (line 615)
* The trim() function:                   Strings.             (line 611)
* Types of messages in Dialog Boxes:     Dialogs.             (line 336)
* Using the console Form Designer:       Fog.                 (line 618)
* Using the Dialogs utility:             Dialogs.             (line 304)
* Using the Kbd utility:                 Kbd.                 (line 193)
* Using the Screen utility:              Screen.              (line 457)
* Using the Strings utility:             Strings.             (line 562)

