Free Pascal CRT 单元常量、变量、函数、过程详解

1、类型,变量,常量:颜色定义:Black = 0;Blue = 1;Green = 2;Cyan = 3;Red = 4;Magenta = 5;Brown = 6;LightGray = 7;DarkGray = 8;LightBlue = 9;LightGreen = 10;LightCyan = 11;LightRed = 12;LightMagenta = 13;Yellow = 14;White = 15;Blink = 128;杂项常数:TextAttr: Byte = $07;TextChar: Char = ' 'CheckBreak: Boolean = Tru

2、e;CheckEOF: Boolean = False;CheckSnow: Boolean = False;DirectVideo: Boolean = False;LastMode: Word = 3;WindMin: Word = $0;WindMax: Word = $184f;ScreenWidth = 80;ScreenHeight = 25;一些变量与Turbo Pascal兼容,但在Free Pascal中,他们没有用处。varcheckbreak : boolean;checkeof : boolean;checksnow : boolean;以下常量定义在DOS系统屏幕模式

3、:Constbw40 = 0;co40 = 1;bw80 = 2;co80 = 3;mono = 7;TextAttr变量控制被写入屏幕字符的属性。var TextAttr : byte;DirectVideo变量控制控制在屏幕上书写。如果为True,游标通过直接设置端口访问,如果为False,然后使用BIOS,这只是DOS下的定义。Lastmode变量告诉你哪种模式是最后被屏幕选择的,它的定义只是基于DOS。var lastmode : Word;过程和函数:1、Procedure AssignCrt (Var F: Text;AssignCrt指定一个文件F到屏幕。写入文件F一切转到屏幕代

4、替。如果屏幕包含一个窗口,全部写在窗口代替。注:功能接近于Writeln。例子:Program Example1;uses Crt;varF : Text;beginAssignCrt(F;Rewrite(F;WriteLn(F,'This is written to the Assigned File'Close(F;end.2、Procedure CursorBig;使光标(不是鼠标图形成为大矩形,在LINUX上不可用。如果不明白的话,运行下面这个程序:Program df;BeginReadln;End.仔细观察效果后,在运行下面这个程序:Program df;Uses

5、crt;BeginCursorBig;Readln;End.仔细对比后你就会知道什么意思了。例子:Program Example9;uses Crt; Program to demonstrate the ClrEol function. var I,J : integer;beginFor I:=1 to 15 doFor J:=1 to 80 dobegingotoxy(j,i;Write(j mod 10;end;Window(5,5,75,12;Write('This line will be cleared from',' here till the righ

6、t of the window'GotoXY(27,WhereY;ReadKey;ClrEol;WriteLn;end.3、Procedure ClrScr;ClrScr清除当前窗口(使用当前的颜色,并设置在当前窗口左上角的光标。(就是清屏例子:Program Example8;uses Crt; Program to demonstrate the ClrScr function. beginWriteln('Press any key to clear the screen'ReadKey;ClrScr;Writeln('Have fun with the

7、cleared screen'end.4、Procedure CursorOff;隐藏光标。在LINUX上无效。5、Procedure CursorOn;显示光标。在LINUX上无效。6、Procedure Delay (DTime: Word;延迟等待指定的毫秒数。指定的秒数是个近似值(即可能有偏差,如果系统负载高,可能被关闭。例子:Program Example15;uses Crt; Program to demonstrate the Delay function. vari : longint;beginWriteLn('Counting Down'for i

8、:=10 downto 1 dobeginWriteLn(i;Delay(1000; Wait one secondend;WriteLn('BOOM!'end.7、Procedure DelLine;DelLine删除当前行。当前行一下的自动向上移动一行,并且在当前窗口底部插入一空行,光标不移动。例子:Program Example10;uses Crt; Program to demonstrate the InsLine function. beginClrScr;WriteLn;WriteLn('Line 1'WriteLn('Line 2

9、9;WriteLn('Line 2'WriteLn('Line 3'WriteLn;WriteLn('Oops, Line 2 is listed twice,',' let''s delete the line at the cursor postion'GotoXY(1,3;ReadKey;DelLine;GotoXY(1,10;end.8、Procedure GotoXY (X: Byte; Y: Byte;光标移动到(x,y处,x指横坐标,y指纵坐标(从窗口顶部开始不包括标题栏。原来的位置(程序编译后一运行

10、时是(1,1,窗口的左上角。例子:Program Example6;uses Crt; Program to demonstrate the GotoXY function. beginClrScr;GotoXY(10,10;Write('10,10'GotoXY(70,20;Write('70,20'GotoXY(1,22;end.9、Procedure HighVideo;高亮显示文本(不是窗口中的所有文本,执行该过程后,读入输出的文本才高亮显示它设置的视频属性高强度位。例子:Program Example14;uses Crt; Program to de

11、monstrate the LowVideo, HighVideo, NormVideo functions. beginLowVideo;WriteLn('This is written with LowVideo'HighVideo;WriteLn('This is written with HighVideo'NormVideo;WriteLn('This is written with NormVideo'end.10、Procedure InsLine;InsLine在当前光标位置插入一个空行,当前行以下的自动向下滚动一行,最后一行从窗

12、口中消失,光标不移动。例子:Program Example10;uses Crt; Program to demonstrate the InsLine function. beginClrScr;WriteLn;WriteLn('Line 1'WriteLn('Line 3'WriteLn;WriteLn('Oops, forgot Line 2, let''s insert at the cursor postion' GotoXY(1,3;ReadKey;InsLine;Write('Line 2'GotoX

13、Y(1,10;end.11、Function KeyPressed : Boolean;KeyPressed函数扫描键盘缓冲区,确认是否有键按下。如果有,则返回True,如果没有,则返回False。Shift、Alt、Ctrl不包括在内。例子:Program Example2; uses Crt; Program to demonstrate the KeyPressed function. begin WriteLn('Waiting until a key is pressed' repeat until KeyPressed; The key is not Read, s

14、o it should also be outputted at the commandline end. 12、Procedure LowVideo; 低亮度显示文本。 13、Procedure NormVideo; NormVideo 以正常亮度显示文本，为默认值。 14、Procedure NoSound; 让扬声器停止发出声音。并不是所有操作系统都支持。 例子： Program Example16; uses Crt; Program to demonstrate the Sound and NoSound function. var i : longint; begin WriteL

15、n('You will hear some tones from your speaker' while (i<15000 do begin inc(i,500; Sound(i; Delay(100; end; WriteLn('Quiet now!' NoSound; Stop noise end. 15、Function ReadKey : Char; ReadKey 从键盘缓冲区读取一个键并返回。如果功能键被按下，则返回 0（ASCII 码） ， 如果执行该函数后并未有键按下，则程序将一直等到有键按下才继续执行下面的 代码。Linux 下的键盘映射

16、可能会导致错误并由 ReadKey 报告，因此需谨慎使用 ReadKey。 例子： Program Example3; uses Crt; Program to demonstrate the ReadKey function. var ch : char; begin writeln('Press Left/Right, Esc=Quit' repeat ch:=ReadKey; case ch of #0 : begin ch:=ReadKey; Read ScanCode case ch of #75 : WriteLn('Left' #77 : Writ

17、eLn('Right' end; end; #27 : WriteLn('ESC' end; until ch=#27 Esc end. 16、Procedure Sound (hz : word; 使扬声器发出 hz 赫兹的声音。在 Windows 下，系统播放声音的频率参数被忽略。 （意思好像是播放的声音的频率和参数有点差距）在在其他操作系统下，此过 程可能不会执行。 17、Procedure TextBackground (CL: Byte; TextBackground 根据参数 CL 设置背景颜色（执行后输入输出文本的） ，CL 为预定 的颜色常量之一

18、。 例子： Program Example13; uses Crt; Program to demonstrate the TextBackground function. begin TextColor(White; WriteLn('This is written in with the default background color' TextBackground(Green; WriteLn('This is written in with a Green background' TextBackground(Brown; WriteLn('T

19、his is written in with a Brown background' TextBackground(Black; WriteLn('Back with a black background' end. 18、Procedure TextColor (CL: Byte; TextColor 根据 CL 设置前景色（执行后输入输出文本的颜色） ，CL 为预定的颜色 常量之一。 例子： Program Example12; uses Crt; Program to demonstrate the TextColor function. begin WriteL

20、n('This is written in the default color' TextColor(Red; WriteLn('This is written in Red' TextColor(White; WriteLn('This is written in White' TextColor(LightBlue; WriteLn('This is written in Light Blue' end. 19、procedure TextMode(Mode: Integer; TextMode 设置屏幕文本模式(即屏幕的行和

21、列数,较低的字节是用于设置 VGA 文本 模式。这个过程只在 DOS 下执行。 20、Function WhereX : Byte; WhereX 返回当前光标的横坐标（相对于当前窗口） 。 例子： Program Example7; uses Crt; Program to demonstrate the WhereX and WhereY functions. begin Writeln('Cursor postion: X=',WhereX,' Y=',WhereY; end. 21、Function WhereY : Byte; WhereY 返回当前光标的纵坐标（相对于当前窗口） 。 例子： Program Example7; uses Crt; Program to demonstrate the WhereX and WhereY functions. begin Writeln('Cursor postion: X=',Wher