addch, waddch, mvaddch, mvwaddch, echochar, wechochar - add a character
   (with attributes) to a curses window, then advance the cursor


   #include <curses.h>

   int addch(const chtype ch);
   int waddch(WINDOW *win, const chtype ch);
   int mvaddch(int y, int x, const chtype ch);
   int mvwaddch(WINDOW *win, int y, int x, const chtype ch);
   int echochar(const chtype ch);
   int wechochar(WINDOW *win, const chtype ch);


   Adding characters
   The addch, waddch, mvaddch and mvwaddch routines put the  character  ch
   into  the  given  window  at its current window position, which is then
   advanced.  They are analogous to putchar in stdio(3).  If  the  advance
   is at the right margin:

   ·   The cursor automatically wraps to the beginning of the next line.

   ·   At  the  bottom of the current scrolling region, and if scrollok is
       enabled, the scrolling region is scrolled up one line.

   ·   If scrollok is not enabled, writing a character at the lower  right
       margin  succeeds.   However, an error is returned because it is not
       possible to wrap to a new line

   If ch is a tab, newline, carriage return or backspace,  the  cursor  is
   moved appropriately within the window:

   ·   Backspace  moves the cursor one character left; at the left edge of
       a window it does nothing.

   ·   Carriage return moves the cursor to the window left margin  on  the
       current line.

   ·   Newline  does  a clrtoeol, then moves the cursor to the window left
       margin on the next line, scrolling the window if on the last line.

   ·   Tabs are considered to be at every eighth column.  The tab interval
       may be altered by setting the TABSIZE variable.

   If  ch  is  any  other  control  character, it is drawn in ^X notation.
   Calling winch after adding a control  character  does  not  return  the
   character  itself,  but  instead  returns  the  ^-representation of the
   control character.

   Video attributes can be combined with a character  argument  passed  to
   addch  or  related  functions by logical-ORing them into the character.
   (Thus, text, including attributes, can be  copied  from  one  place  to
   another  using inch and addch.)  See the attr(3NCURSES) page for values
   of predefined video attribute constants that can be usefully OR'ed into

   Echoing characters
   The  echochar  and wechochar routines are equivalent to a call to addch
   followed by a call to refresh, or a call to waddch followed by  a  call
   to  wrefresh.   The  knowledge  that  only  a single character is being
   output  is  used  and,  for  non-control  characters,  a   considerable
   performance  gain  may be seen by using these routines instead of their

   Line Graphics
   The following variables may be used to add line drawing  characters  to
   the  screen  with  routines of the addch family.  The default character
   listed below is used if the acsc capability does not define a terminal-
   specific   replacement   for   it,   or  if  the  terminal  and  locale
   configuration requires  Unicode  but  the  library  is  unable  to  use

   The names are taken from VT100 nomenclature.

   Name           Default   Description
   ACS_BLOCK      #         solid square block
   ACS_BOARD      #         board of squares
   ACS_BTEE       +         bottom tee
   ACS_BULLET     o         bullet
   ACS_CKBOARD    :         checker board (stipple)
   ACS_DARROW     v         arrow pointing down
   ACS_DEGREE     '         degree symbol
   ACS_DIAMOND    +         diamond
   ACS_GEQUAL     >         greater-than-or-equal-to
   ACS_HLINE      -         horizontal line
   ACS_LANTERN    #         lantern symbol
   ACS_LARROW     <         arrow pointing left
   ACS_LEQUAL     <         less-than-or-equal-to
   ACS_LLCORNER   +         lower left-hand corner
   ACS_LRCORNER   +         lower right-hand corner
   ACS_LTEE       +         left tee
   ACS_NEQUAL     !         not-equal
   ACS_PI         *         greek pi
   ACS_PLMINUS    #         plus/minus
   ACS_PLUS       +         plus
   ACS_RARROW     >         arrow pointing right
   ACS_RTEE       +         right tee
   ACS_S1         -         scan line 1
   ACS_S3         -         scan line 3
   ACS_S7         -         scan line 7
   ACS_S9         _         scan line 9
   ACS_STERLING   f         pound-sterling symbol
   ACS_TTEE       +         top tee
   ACS_UARROW     ^         arrow pointing up
   ACS_ULCORNER   +         upper left-hand corner
   ACS_URCORNER   +         upper right-hand corner
   ACS_VLINE      |         vertical line


   All routines return the integer ERR upon failure and OK on success (the
   SVr4 manuals specify only "an  integer  value  other  than  ERR")  upon
   successful  completion, unless otherwise noted in the preceding routine

   Functions with a "mv" prefix first  perform  a  cursor  movement  using
   wmove, and return an error if the position is outside the window, or if
   the window pointer is null.


   Note that addch, mvaddch, mvwaddch, and echochar may be macros.


   All these functions are described in the XSI Curses standard, Issue  4.
   The  defaults specified for forms-drawing characters apply in the POSIX

   X/Open Curses states that the ACS_ definitions are char constants.  For
   the   wide-character   implementation  (see  curs_add_wch),  there  are
   analogous WACS_ definitions which are cchar_t constants.

   Some ACS  symbols  (ACS_S3,  ACS_S7,  ACS_LEQUAL,  ACS_GEQUAL,  ACS_PI,
   ACS_NEQUAL,  ACS_STERLING) were not documented in any publicly released
   System V.  However, many  publicly  available  terminfos  include  acsc
   strings  in  which  their  key characters (pryz{|}) are embedded, and a
   second-hand list of their character descriptions  has  come  to  light.
   The ACS-prefixed names for them were invented for ncurses(3NCURSES).

   The displayed values for the ACS_ and WACS_ constants depend on

   ·   the library configuration, i.e., ncurses versus ncursesw, where the
       latter is capable of displaying Unicode while the  former  is  not,

   ·   whether the locale uses UTF-8 encoding.

   In  certain  cases,  the  terminal  is  unable  to display line-drawing
   characters   except   by   using   UTF-8   (see   the   discussion   of
   NCURSES_NO_UTF8_ACS in ncurses(3X)).

   The  TABSIZE variable is implemented in some versions of curses, but is
   not part of X/Open curses.

   If ch is a carriage return, the cursor is moved to the beginning of the
   current  row of the window.  This is true of other implementations, but
   is not documented.


   ncurses(3NCURSES),  attr(3NCURSES),  clear(3NCURSES),   inch(3NCURSES),
   outopts(3NCURSES),    refresh(3NCURSES),    curses_variables(3NCURSES),

   Comparable functions  in  the  wide-character  (ncursesw)  library  are
   described in add_wch(3NCURSES).



Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.