Tuesday, 28 August 2012

Pascal Programming Lesson #2 - Colors, Coordinates, Windows and Sound


Colors

To change the color of the text printed on the screen we use the TextColor command.

program Colors;

uses
   crt;

begin
   TextColor(Red);
   Writeln('Hello');
   TextColor(White);
   Writeln('world');
end.

The TextBackground command changes the color of the background of text. If you want to change the whole screen to a certain color then you must use ClrScr.

program Colors;

uses
   crt;

begin
   TextBackground(Red);
   Writeln('Hello');
   TextColor(White);
   ClrScr;
end.

Screen coordinates

You can put the cursor anywhere on the screen using the GoToXY command. In DOS, the screen is 80 characters wide and 25 characters high. The height and width varies on other platforms. You may remember graphs from Maths which have a X and a Y axis. Screen coordinates work in a similar way. Here is an example of how to move the cursor to the 10th column in the 5th row.

program Coordinates;

uses
   crt;

begin
   GoToXY(10,5);
   Writeln('Hello');
end.

Windows

Windows let you define a part of the screen that your output will be confined to. If you create a window and clear the screen it will only clear what is in the window. The Window command has 4 parameters which are the top left coordinates and the bottom right coordinates.

program Coordinates;

uses
   crt;

begin
   Window(1,1,10,5);
   TextBackground(Blue);
   ClrScr;
end.

Using window(1,1,80,25) will set the window back to the normal size.

Sound

The Sound command makes a sound at the frequency you give it. It does not stop making a sound until theNoSound command is used. The Delay command pauses a program for the amount of milliseconds you tell it to. Delay is used between Sound and NoSound to make the sound last for a certain amount of time.

program Sounds;

uses
   crt;

begin
   Sound(1000);
   Delay(1000);
   NoSound;
end.

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