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%----------------------------------------------------------------------------
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\chapter{The Console Library}
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%----------------------------------------------------------------------------
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The output on the screen in text mode is supported by a group of functions that
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act on the whole screen and modify, each time, the cursor's position. Since such
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functions are not reentrant, they must be used in mutual exclusion.
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In order to use the library for displaying on the screen, the
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``\texttt{cons.h}'' file must be included. This file contains the values for
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the usable colors whose symbolic names are listed below: \texttt{BLACK, BLUE,
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GREEN, CYAN, RED, MAGENTA, BROWN, GRAY, LIGHTGRAY, LIGHTBLUE, LIGHTGREEN,
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LIGHTCYAN, LIGHTRED, LIGHTMAGENTA, YELLOW, WHITE}.
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Two global read-only variables \texttt{cons\_columns} and \texttt{cons\_rows}
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contain the number of screen columns and the number of screen rows,
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respectively. They can be used to write applications that are indipendent from
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the screen dimensions.
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\vspace{7mm}
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\begin{intest}
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CPUTC, CPUTS, CPRINTF \index{cputc()}\index{cputs()}\index{cprintf()}
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\end{intest}
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\begin{description}
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\item [\textbf{void cputc(char c); }]
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\item [\textbf{void cputs(char {*}s); }]
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\item [\textbf{int cprintf(char {*}fmt,... ); }]
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\item [\textbf{Description:}] \texttt{cputc}, \texttt{cupts} and \texttt{cprintf} are used
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to print on the screen a character, a string, or a formatted string,
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respectively. In the latter case, the standard C I/O formatting conventions are
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used.
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\item [\textbf{Warning:}]since these functions modify the cursor position, they are not
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reentrant, and must be used in a mutually exclusive fashion.
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\end{description}
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\begin{intest}
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PUTC\_XY, PUTS\_XY, PRINTF\_XY, GETC\_XY \index{putc\_xy()} \index{puts\_xy()}
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\index{printf\_xy()} \index{getc\_xy()}
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\end{intest}
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\begin{description}
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\item [\textbf{void putc\_xy(int x,int y,char attr,char c) }]
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\item [\textbf{void puts\_xy(int x,int y,char attr,char {*}s) }]
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\item [\textbf{int printf\_xy(int x,int y,char attr,char {*}fmt,...) }]
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\item [\textbf{char getc\_xy(int x,int y,char {*}attr,char {*}c) }]
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\item [\textbf{Description:}] These functions are similar to the previously defined ones;
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the only difference is that since they're reentrant can be used concurrently by
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multiple tasks (the others cannot be used for this purpose because they modify
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the cursor's state). \texttt{getc\_xy} is used to read the charcater and its
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attribute at a specific position on the screen.
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\end{description}
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\begin{intest}
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CLEAR, \_CLEAR, SCROLL, \_SCROLL \index{clear()} \index{\_clear()}
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\index{\_scroll()}
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\end{intest}
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\begin{description}
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\item [\textbf{void \_clear(char c,char attr,int x1,int y1,int x2,int y2) }]
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\item [\textbf{void clear(void) }]
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\item [\textbf{void \_scroll(char attr,int x1,int y1,int x2,int y2) }]
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\item [\textbf{void scroll(void) }]
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\item [\textbf{Description:}] the \texttt{clear} and \texttt{scroll} functions are used
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for clearing the screen and for scrolling it upwards. They are based on the
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\texttt{\_clear()} and \texttt{\_scroll()} functions used for clearing or
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scrolling a window (defined by \texttt{x1, y1, x2, y2}) by filling the area with
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\texttt{attr} color and, in the case of \texttt{\_clear}, with character
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\texttt{c} as well.
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\end{description}
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\begin{intest}
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SET\_ACTIVE\_PAGE, SET\_VISUAL\_PAGE,\\
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GET\_ACTIVE\_PAGE, GET\_VISUAL\_PAGE
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\index{set\_active\_page()} \index{set\_visual\_page()}
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\index{get\_active\_page()} \index{get\_visual\_page()}
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\end{intest}
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\begin{description}
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\item [\textbf{void set\_active\_page(int page) }]
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\item [\textbf{void set\_visual\_page(int page) }]
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\item [\textbf{int get\_active\_page(void) }]
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\item [\textbf{int get\_visual\_page(void) }]
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\item [\textbf{Description:}] The video cards working in text mode use the CGA hardware
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scheme. In this scheme, every screen occupies 4000 bytes (80 columns x 25 rows;
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each position is associated with two bytes, one for codifying the character and
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another for codifying the color). The video card memory is in general bigger,
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therefore multiple screen pages can be used simultaneously. The currently
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visualized screen is called the \texttt{visual page}, whereas the screen the
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output is directed to is called the \texttt{active page}. The cited functions
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are essentially used for handling, at a given instant, the visual page or the
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active page. SUGGESTION: if the active page or the visual page are modified,
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they should be restored to the original (0) value on exit; the same is true for
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the cursor.
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\end{description}
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\begin{intest}
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PLACE, CURSOR, CURSOR\_INFO
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\index{place()} \index{cursor()} \index{cursor\_info()}
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\end{intest}
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\begin{description}
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\item [\textbf{void place(int x, int y) }]
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\item [\textbf{void cursor(int start\_scanline, int end\_scanline) }]
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\item [\textbf{void cursor\_info(int {*}x, int {*}y) }]
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\item [\textbf{Description:}] These functions are used for handling the cursor. More
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specifically, \texttt{place} sets the cursor position (\texttt{x} belongs to the
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range 0\ldots{}79, \texttt{y} to 0\ldots{}24).
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\end{description}
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\begin{intest}
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CURSOR\_BLOB, CURSOR\_STD, CURSOR\_OFF
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\index{cursor\_blob()} \index{cursor\_std()} \index{cursor\_off()}
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\end{intest}
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\begin{description}
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\item [\textbf{void cursor\_blob(void) }]
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\item [\textbf{void cursor\_std(void) }]
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\item [\textbf{void cursor\_off(void) }]
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\item [\textbf{Description:}] These macros call the \texttt{cursor()} function to set the
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cursor shape to be a big rectangle, the standard underscore, or invisible.
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\end{description}