GameDev with QBasic

Video - https://youtu.be/CcdA_uz_GEQ
This month’s topic is game development history featuring QBasic. We discuss how we got started with game development and the first tools and languages that we used. Levi D. Smith shows how to setup QBasic using DOSBox and a brief overview of the language.

Transcript

1. GameDev with QBasic 2019 Levi D. Smith
2. History • BASIC – Beginner’s All-purpose Symbolic Instruction Code • QBasic standard on DOS 5.0 command prompt
3. Running QBasic with DosBox • Install DOSBox • Recommended defaults • windowresolution=1024x768 • Output=opengl • [autoexec] mount C “C:\program files (x86)\DOSBox-0.74\qbasic” • Download Qbasic executable • Set default folder • C:\Users\<user>\AppData\Local\DOSBox\dosbox-<version>.conf • Filenames must be 8.3 format
4. Example Qbasic Games • Before Internet access, all we had was looking at example code • Nibbles • Gorilla • Programming books weren’t prevalent at book stores • QBasic comes with built-in help pages
5. Using QBasic • Shift + F5 - Run Game • F2 - View Subs • Alt, F, O - Load program • Ctrl + C - end program
6. A Simple Game PRINT display text and variables INPUT read input from user DO WHILE / LOOP control structure IF THEN, ELSEIF, ELSE, END IF control structure >, <, <>, = comparison operators = assignment RANDOMIZE TIMER, RND generate random number INT cast as integer + Arithmetic
7. A Simple Game
8. Drawing Primitives – Lines and Rectangles • Screen Mode • SCREEN 7 – 320x200, 16 colors • SCREEN 12 – 640x480, 256K colors • Lines and Rectangles • From, To, Color, Type
9. Drawing Primitives - Circles • Circles • Center, Radius, Color, Start Angle, End Angle, Aspect Ratio • Filled Circle • Paint – location, fill color, border color • Slow
10. Drawing Shapes • Define pen movements (up, down, left, right, etc) with unit distance as a string • Use BM to set starting point
11. Displaying Text • Use LOCATE x, y to set text position • PRINT to display strings and variables • Separate parameters with semicolon (;) • Comma (,) separated parameters will be extra spaced
12. Playing Music • Use Play with string • O – Octave • L – Length • CDEFGAB – Notes • Sound (frequency, duration)
13. Structures • TYPE to define structure • data types – INTEGER, LONG, SINGLE, DOUBLE, STRING • DIM to instantiate • Array – DIM foo(1 TO N) AS TYPE
14. Procedures • F2 – show procedures • SUB – Sub procedure (does not return a value) • Can pass custom types (define type before sub declaration) • FUNCTION – Returns a value • Assign value to function name (don’t use “return”) • Global variable – use COMMON SHARED
15. User Input • Read keyboard with INKEY$ • IBM PC Keyboard Scan Codes • http://www.jimprice.com/jim-asc.shtml#keycodes • Arrows • Up: CHR$(0) + CHR$(72) • Down: CHR$(0) + CHR$(80) • Right: CHR$(0) + CHR$(77) • Left: CHR$(0) + CHR$(75)
16. Delay • FOR a# = 1 TO curSpeed: NEXT a#
17. References • https://bitbucket.org/dylanwolf/oldgames/src/default/ • https://github.com/gatechgrad/QBasicMiniGames • https://www.dosbox.com/ • https://www.qbasic.net/ • http://www.petesqbsite.com/