Tiny Christmas Star (Tiny BASIC)
Author: Marco's Retrobits (Marco Varesio)
Category: Christmas Challenge
System: Classic and modern systems running ITTY BITTY TinyBASIC and derivatives (e.g. Cosmac ELF, Netronics ELF II, TinyBASICBlazor)
Language: Tiny BASIC
Len source code: 203 bytes
Len exe file: N/A (only text program listing is provided)
Len code only: N/A (valid for assembler only; length of executable without BASIC stub)
Instructions:
TinyBASICBlazor (for WebAssembly capable web browsers):
Go to https://retrobits.altervista.org/tinybasicblazor/, click the "Browse..." button on the bottom left, choose the "source.txt" file and enjoy!
Emma 02 emulator (Windows instructions - for other host systems should be similar):
Install the Emma 02 emulator and support files; select the "ELF" tab and "Cosmac ELF" in the combo box.
Then load the Netronics Tiny BASIC configuration from the menu: "File" -> "Configuration" -> "Load" -> "Netronics Tiny Basic" -> "Serial I/O" and then click the "Start" button.
The "Elf - VT 100" window will pop up. Wait a few seconds, then press the "Return" (or "Enter") key twice.
Open the "source.txt" file with a text editor, select all text and copy it (CTRL+C).
Go to the "Elf - VT 100" windows and paste the copied text (CTRL+V).
Wait a few seconds, then press the "Return" (or "Enter") key, type "RUN" and then press the "Return" (or "Enter") key again.
Enjoy!
Description:
The program iterates over each cell of a 17 characters wide square.
If the "point" belongs to one of the following four triangles, a "*" is printed; otherwise a " " is printed.
*
**
***
****
*****
******
*******
********
*********
**********
***********
************
*************
*
**
***
****
*****
******
*******
********
*********
**********
***********
************
*************
*************
************
***********
**********
*********
********
*******
******
*****
****
***
**
*
*************
************
***********
**********
*********
********
*******
******
*****
****
***
**
*
Tiny Christmas Star program listing:
1R=0
2C=0
3S=0
4IFR<13IFC>3IFC<R+5S=1
5IFR<13IFC<13IFC>11-RS=1
6IFR>3IFC<13IFC>R-5S=1
7IFR>3IFC>3IFC<21-RS=1
8IFS=0PR" ";
9IFS=1PR"*";
10C=C+1
11IFC<17GOTO3
12PR
13R=R+1
14IFR<17GOTO2
15END
Verbose program listing:
100 LET R=0
110 LET C=0
120 LET S=0
130 IF R<13 THEN IF C>3 THEN IF C<R+5 THEN LET S=1
140 IF R<13 THEN IF C<13 THEN IF C>11-R THEN LET S=1
150 IF R>3 THEN IF C<13 THEN IF C>R-5 THEN LET S=1
160 IF R>3 THEN IF C>3 THEN IF C<21-R THEN LET S=1
800 IF S=0 THEN PRINT " ";
810 IF S=1 THEN PRINT "*";
900 LET C=C+1
910 IF C<17 THEN GOTO 120
915 PRINT
920 LET R=R+1
930 IF R<17 THEN GOTO 110
1000 END
Output:
* *
** **
*** ***
**** ****
*****************
***************
*************
***********
*********
***********
*************
***************
*****************
**** ****
*** ***
** **
* *
Comments:
The original Tiny BASIC grammar does not include FOR loops, so IFs and GOTOs are used instead.
See: http://www.ittybittycomputers.com/ittybitty/tinybasic/TBuserMan.htm#Syntax
The (verbose version of the) program is so simple that it can be ported to most BASIC dialects (BBC Basic, Sinclair ZX81) (almost) without modifications.
See the program in action:
Cosmac ELF (Emma 02 emulator): https://www.youtube.com/watch?v=7xElR66LwwQ&t=54s
TinyBASICBlazor: https://www.youtube.com/watch?v=i2EJBGYvd0E