Chapter 8: Advanced Statements in QBasic | CBSE Class 7 Computer

🎨 QBasic Graphic Statements Explained

QBasic's graphic statements allow you to create shapes, colors, and sound in your programs, making learning coding more fun and creative!

🖥️ GRAPHIC MODE - SCREEN & RESOLUTION

• SCREEN statement: Sets the display mode (resolution and color levels) required for drawing graphics.
  SCREEN mode_number
• Common Modes:

  Mode	Resolution	Colors
  0	Text only	-
  1	320x200	4 colors
  2	640x200	2 colors
  12	640x480	16 colors

Example:
SCREEN 1

🌈 COLOR STATEMENT

• COLOR sets the foreground and background colors for text or graphics.
• COLOR foreground, background
• Some color codes:

  Color	Code
  Black	0
  Blue	1
  Green	2
  Red	4
  White	7
  Yellow	14

Example:
COLOR 4, 7
(Red text on white background)

⬛ PIXEL, PSET and PRESET

• To color or read an individual pixel:
• PSET (x, y), color plots a single pixel.
• PRESET (x, y), color erases or puts background color at position.

Example:
PSET (100, 150), 14 ('Draws yellow pixel at 100,150)

📏 LINE Statement

• LINE (x1, y1)-(x2, y2), color draws a line from (x1, y1) to (x2, y2).
• B option: draws a rectangle.
  BF option: draws a filled box.

Draw a line:
LINE (50,60)-(180,160), 2

Draw a square box (side=50):
LINE (60,60)-(110,110), 3, B

⚪ CIRCLE Statement

• CIRCLE (x, y), radius, color draws a circle with given center and radius.

Example:
CIRCLE (120,100), 40, 4 ('Red Circle)

🪄 PAINT Statement

• Fills an area with color starting from (x, y).
• PAINT (x, y), color, bordercolor

Example:
PAINT (120,100), 6, 4
Paints area from (120,100) with color 6 inside a red border (color 4).

✏️ DRAW Statement (Turtle Graphics)

• Draws graphics using codes D, U, R, L, E, F, G, H (directions).
• D: Down, U: Up, R: Right, L: Left, E: Up-Right, F: Down-Right, G: Down-Left, H: Up-Left
• Syntax: DRAW "code" (e.g., DRAW "R50" moves right 50 units)

Code	Direction
D	Down
U	Up
R	Right
L	Left
E	Up-Right
F	Down-Right
G	Down-Left
H	Up-Left

Example:
DRAW "R80D80L80U80" (Draws a square)

🔊 SOUND & BEEP Statements

• BEEP: Simple short sound.
  BEEP
• SOUND: Plays tone at selected frequency for specified time.
  SOUND frequency, duration
  (frequency in Hz, duration in 1/18 sec)

Example:
BEEP (Beep Sound)
SOUND 800, 10 (Tone at 800Hz for short time)

🚦 Unconditional and Exit Statements

• END: Stops the program instantly.
  END
• EXIT: Used to exit loop early.
  EXIT FOR
EXIT DO

Example:

FOR I = 1 TO 10
  IF I = 5 THEN EXIT FOR
  PRINT I
NEXT I
    

(Prints 1 to 4, then exits loop)

🔀 GOSUB ... RETURN Statement

• Jumps to a subroutine, then goes back to next statement after GOSUB.
• GOSUB label ... RETURN

Example:

PRINT "Start"
GOSUB PrintMessage
PRINT "End"
END

PrintMessage:
PRINT "This is a subroutine"
RETURN
    

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