Crt unit

This chapter describes the CRT unit for Free Pascal, under all of Dos, Linux and Windows. The unit was first written for Dos by Florian Klaempfl. The unit was ported to Linux by Mark May and enhanced by Michael Van Canneyt and Peter Vreman. It works on the Linux console, and in xterm and rxvt windows under X-Windows. The functionality for both is the same, except that under Linux the use of an early implementation (versions 0.9.1 and earlier of the compiler) the CRT unit automatically cleared the screen at program startup.

There are some caveats when using the CRT unit:

• Programs using the CRT unit will not be usable when input/output is being redirected on the command-line.
• For similar reasons they are not usable as CGI-scripts for use with a webserver.
• The use of the CRT unit and the graph unit may not always be supported.
• The CRT unit is not thread safe.
• On Linux or other Unix OSes, executing other programs that expect special terminal behaviour (using one of the special functions in the Linux unit) will not work. The terminal is set in RAW mode, which will destroy most terminal emulation settings.
• The CRT unit stems from the TP/Dos area. It is designed to work with single-byte character sets, where 1 char = 1 byte. That means that widestrings or UTF-8 encoded (ansi)strings will not work correctly.

Procedures and functions

AssignCrt	procedure	Assign file to CRT.
ClrEol	procedure	Clear from cursor position till end of line.
ClrScr	procedure	Clear current window.
cursorbig	procedure	Show big cursor.
cursoroff	procedure	Hide cursor.
cursoron	procedure	Display cursor.
Delay	procedure	Delay program execution.
DelLine	procedure	Delete line at cursor position.
GotoXY	procedure	Set cursor position on screen.
HighVideo	procedure	Switch to highlighted text mode.
InsLine	procedure	Insert an empty line at cursor position.
KeyPressed	function	Check if there is a keypress in the keybuffer.
LowVideo	procedure	Switch to low intensity colors.
NormVideo	procedure	Return to normal (startup) modus.
NoSound	procedure	Stop system speaker.
ReadKey	function	Read key from keybuffer.
Sound	procedure	Sound system speaker.
TextBackground	procedure	Set text background.
TextColor	procedure	Set text color.
TextMode	procedure	Set screen mode.
WhereX	function	Return X (horizontal) cursor position.
WhereY	function	Return Y (vertical) cursor position.
Window	procedure	Create new window on screen.

Types

tcrtcoord

type

Type to denote CRT coordinates.

Constants

Black	constant	Black color attribute.
Blink	constant	Blink attribute.
Blue	constant	Blue color attribute.
Brown	constant	Brown color attribute.
BW40	constant	40 columns black and white screen mode.
BW80	constant	80 columns black and white screen mode.
C40	constant	40 columns color screen mode.
C80	constant	80 columns color screen mode.
CO40	constant	40 columns color screen mode.
CO80	constant	80 columns color screen mode.
Cyan	constant	Cyan color attribute.
DarkGray	constant	Dark gray color attribute.
Font8x8	constant	Internal ROM font mode.
Green	constant	Green color attribute.
LightBlue	constant	Light Blue color attribute.
LightCyan	constant	Light cyan color attribute.
LightGray	constant	Light gray color attribute.
LightGreen	constant	Light green color attribute.
LightMagenta	constant	Light magenta color attribute.
LightRed	constant	Light red color attribute.
Magenta	constant	Magenta color attribute.
Mono	constant	Monochrome screen mode (hercules screens).
Red	constant	Red color attribute.
ScreenHeight	constant	Current screen height.
ScreenWidth	constant	Current screen width.
White	constant	White color attribute.
Yellow	constant	Yellow color attribute.

Variables

CheckBreak	variable	Check for CTRL-Break keystroke. Not used.
CheckEOF	variable	Check for EOF on standard input. Not used.
CheckSnow	variable	Check snow on CGA screens. Not used.
DirectVideo	variable	Use direct video access. DOS only.
LastMode	variable	Last screen mode.
TextAttr	variable	Mask to filter text attribute.
WindMax	variable	Lower right corner of currently defined window.
WindMaxX	variable	X coordinate of lower right corner of the defined window.
WindMaxY	variable	Y coordinate of lower right corner of the defined window.
WindMin	variable	Upper left corner of currently defined window.
WindMinX	variable	X coordinate of upper left corner of the defined window.
WindMinY	variable	Y coordinate of upper left corner of the defined window.