SuperBASIC: Difference between revisions

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(Adding how to use OR | AND in IF statements)
(→‎Control characters for cursor and colour control: re-ordered by number, added chr$(11) and 13.)
 
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''Debugging hint: If you encounter an error like "open structure" or "endproc without a proc": do not trust the line number that you are given. The root of the problem is probably in a structure earlier on in the code.''
''Debugging hint: If you encounter an error like "open structure" or "endproc without a proc": do not trust the line number that you are given. The root of the problem is probably in a structure earlier on in the code.''


===== Ealuating multiple conditions in IF statements =====
===== Evaluating multiple conditions in IF statements =====
SUPERBASIC don't have the dedicated keywords AND , OR so you have to use the bitwise operators to evaluate multiple conditions, please consider the following examples:
SUPERBASIC doesn't have the dedicated keywords AND , OR so you have to use the bitwise operators to evaluate multiple conditions, please consider the following examples:


* AND  if (a=1)&(b=2) then c=1
* AND  <code>if (a=1)&(b=2) then c=1</code>
* OR   if (a=1)^(b=2) then c=1
* OR   <code>if (a=1)^(b=2) then c=1</code>


These should work as long as you use parenthesis in all evaluated expressions (makes bitwise operators behave like logical).
This should work as long as you use parenthesis in all evaluated expressions (Since parenthesis makes bitwise operators behave like logical operators).


===== Using procedures =====
===== Using procedures =====
Line 64: Line 64:
|<code>ctrl-i</code>
|<code>ctrl-i</code>
|Move cursor 8 characters to the right  
|Move cursor 8 characters to the right  
|-
|<code>ctrl-k</code>
|Deletes characters from cursor position to line end
|}
|}


Line 78: Line 81:
!Effect
!Effect
|-
|-
|chr$(12)
|chr$(1)
|Clear screen and set cursor to upper left corner
|Set cursor to leftmost position in current line
|-
|chr$(16)
|Cursor up
|-
|chr$(14)
|Cursor down
|-
|-
|chr$(2)
|chr$(2)
|Cursor left
|Cursor left
|-
|chr$(5)
|Set cursor to righmost position in current line
|-
|-
|chr$(6)
|chr$(6)
|Cursor right
|Cursor right
|-
|-
|chr$(1)
|chr$(11)
|Set cursor to leftmost position in current line
|Deletes characters from cursor position to line end
|-
|chr$(12)
|Clear screen and set cursor to upper left corner
|-
|chr$(13)
|Move cursor to start of next line
|-
|chr$(14)
|Cursor down
|-
|-
|chr$(5)
|chr$(16)
|Set cursor to righmost position in current line
|Cursor up
|-
|-
|chr$(128) - chr$(143)
|chr$(128) - chr$(143)
Line 151: Line 160:
|White
|White
|}
|}
===== Character Set / Text matrix =====
* Access to the full character set can be obtained by using the <code>CPRINT</code> command instead of the normal <code>PRINT</code> command.
* Characters can also be set on the screen text matrix using the <code>POKE</code> command starting at <code>$C000</code> providing the MMU I/O control is set to 2 by executing a <code>POKE 1,2</code> command first (remember to restore the MMU I/O once you're done).
[[File:Full char set.png|thumb|104x104px|F256 Character Set|none]]
* Color can also be set on the screen color matrix using the <code>POKE</code> command starting at <code>$C000</code> providing the MMU I/O control is set to 3 by executing a <code>POKE 1,3</code> command first (remember to restore the MMU I/O once you're done).
* When poking colors on the screen, the high nibble is the character color and  the low nibble is the background color.
[[File:Colormatrix.png|alt=Default Colors|thumb|100x100px|Default Colors|none]]
===== Memcopy lockup =====
* In certain situations the <code><big>memcopy</big></code> command can lockup.
* A machine language utility that performs the same function as <code>memcopy</code> is available if <code>memcopy</code> fails.
* <u>mlcopy</u> is a short routine that replaces <code>memcopy</code> and is more reliable. It can be loaded into memory with a BLOAD command in your program, or with a basic loader that can be added to your program.
* In place of the <code>memcopy</code> command you would use 3 <code><big>POKEL</big></code> commands and a <code><big>CALL</big></code> command to engage the DMA engine.
<code>POKEL $0903,data source</code>
<code>POKEL $0906,destination</code>
<code>POKEL $0909,number of bytes to copy</code>
<code>CALL $0900</code>
* [https://github.com/mcassera/F256-mlcopy mlcopy github page]
===== Sprite Images =====
In BASIC you can access different SPRITE shapes through the IMAGE command as part of the sprite command: <code>SPRITE 0 IMAGE 1 TO 100,100</code>. Be aware that BASIC can only keep track of 64 Images, if you want to access and show more than 64 different shapes you need to poke the 3 bytes of the address where the image data resides into the correct sprite registers yourself.
===== Sprite Coordinates =====
In BASIC all sprites are centered on the coordinate specified, this might produce some counterintuitive effects when using different size sprites, for example if you want to align the sprite edge with the top left side of the screen you would need different values depending on the sprite size
<code>SPRITE 0 IMAGE 1 TO 4,4: REM "8x8 Sprite"</code></BR>
<code>SPRITE 1 IMAGE 1 TO 8,8: REM "16x16 Sprite"</code></BR>
<code>SPRITE 2 IMAGE 2 TO 12,12: REM "24x24 Sprite"</code></BR>
<code>SPRITE 3 IMAGE 3 TO 16,16: REM "32x32 Sprite"</code></BR>
Also, please note that you need to use the command <code>SPRITE X IMAGE Y</code> before setting the sprite coordinates or else BASIC will not know what size is the sprite, and will misalign it, for example the following code although it seems correct will misalign the sprite:
<code>SPRITE 1 TO 8,8</code></BR>
<code>SPRITE 1 IMAGE 1: REM "USe a 16x16 Sprite"</code></BR>

Latest revision as of 19:50, 24 October 2024

SuperBASIC is inspired by BBC BASIC but offers quite a bit more.

An informal list of tips, "gotchas":[edit | edit source]

IF, THEN, ELSE[edit | edit source]
Source of this tip: Ernesto[edit | edit source]
  • A regular if then condition can't contain an else statement, as in this example:

10 if a=0 then x=10

  • If you need to do an if then else structure, you actually have to do an if else endif structure like in the following example, skipping the then statement.

10 if a=0
20 x=1
30 else
40 x=2
50 endif

  • If you do it in one line it needs to have some colons added, making it look weird like this:

10 if a=0:x=1:else:x=2:endif

  • if you dare to omit the endif thinking that the if statement won't need it, (mmm.., everything is in one line, so no need, right?) -Nope...all hell breaks loose!-

10 if a=0:x=1:else:x=2: REM "<-- Error, omited the endif"

  • be careful not to add an extra then statement by mistake to an if else endif structure, if you do -All hell breaks loose again!!-

10 if a=0 then  : rem "<-- Error, THEN is not needed!!!"
20 x=1
30 else
40 x=2
50 endif

Debugging hint: If you encounter an error like "open structure" or "endproc without a proc": do not trust the line number that you are given. The root of the problem is probably in a structure earlier on in the code.

Evaluating multiple conditions in IF statements[edit | edit source]

SUPERBASIC doesn't have the dedicated keywords AND , OR so you have to use the bitwise operators to evaluate multiple conditions, please consider the following examples:

  • AND if (a=1)&(b=2) then c=1
  • OR if (a=1)^(b=2) then c=1

This should work as long as you use parenthesis in all evaluated expressions (Since parenthesis makes bitwise operators behave like logical operators).

Using procedures[edit | edit source]
  • The proc keyword is only valid if it appears after an end statement.
  • When calling a procedure use the procedure name followed by parenthesis (), even if the procedure has no parameters.
  • Avoid any space between the procedure name and the parenthesis, else it will produce an error.
Keyboard shortcuts[edit | edit source]
Key combination Effect
ctrl-c or RUN STOP on the F256K Stops a listing or a running program
ctrl-l Clears the screen
ctrl-a or CLR/HOME on the F256K Move cursor to the first character in the current line
ctrl-e Move cursor to the last character in the current line
ctrl-i Move cursor 8 characters to the right
ctrl-k Deletes characters from cursor position to line end
Behaviour of load and bload[edit | edit source]
  • The bload statement does not print Completed when loading is successfull whereas load does.
  • bload can load anywhere on memory not just under the first 64k
  • An exception is that bload can't load I/O parameters that reside in $C000 - $DFFF
Control characters for cursor and colour control[edit | edit source]

In BASIC the following character codes can be used with print to control the cursor position and colours on the screen.

Code Effect
chr$(1) Set cursor to leftmost position in current line
chr$(2) Cursor left
chr$(5) Set cursor to righmost position in current line
chr$(6) Cursor right
chr$(11) Deletes characters from cursor position to line end
chr$(12) Clear screen and set cursor to upper left corner
chr$(13) Move cursor to start of next line
chr$(14) Cursor down
chr$(16) Cursor up
chr$(128) - chr$(143) Set foreground color. Code 128 is black 143 is white. The rest follows the sequence given below
chr$(144) - chr$(159) Set background color. Code 144 is black 159 is white. The rest follows the sequence given below
Colour code Colour Colour code Colour
0 Black 8 Dark grey
1 Grey 9 Light grey (default foreground)
2 Dark blue (default background colour) 10 Blue
3 Green 11 Light green
4 Purple 12 Light purple
5 Brown 13 Red
6 Orange 14 Yellow
7 Light blue 15 White
Character Set / Text matrix[edit | edit source]
  • Access to the full character set can be obtained by using the CPRINT command instead of the normal PRINT command.
  • Characters can also be set on the screen text matrix using the POKE command starting at $C000 providing the MMU I/O control is set to 2 by executing a POKE 1,2 command first (remember to restore the MMU I/O once you're done).
F256 Character Set
  • Color can also be set on the screen color matrix using the POKE command starting at $C000 providing the MMU I/O control is set to 3 by executing a POKE 1,3 command first (remember to restore the MMU I/O once you're done).
  • When poking colors on the screen, the high nibble is the character color and the low nibble is the background color.
Default Colors
Default Colors
Memcopy lockup[edit | edit source]
  • In certain situations the memcopy command can lockup.
  • A machine language utility that performs the same function as memcopy is available if memcopy fails.
  • mlcopy is a short routine that replaces memcopy and is more reliable. It can be loaded into memory with a BLOAD command in your program, or with a basic loader that can be added to your program.
  • In place of the memcopy command you would use 3 POKEL commands and a CALL command to engage the DMA engine.
POKEL $0903,data source
POKEL $0906,destination 
POKEL $0909,number of bytes to copy
CALL $0900
Sprite Images[edit | edit source]

In BASIC you can access different SPRITE shapes through the IMAGE command as part of the sprite command: SPRITE 0 IMAGE 1 TO 100,100. Be aware that BASIC can only keep track of 64 Images, if you want to access and show more than 64 different shapes you need to poke the 3 bytes of the address where the image data resides into the correct sprite registers yourself.

Sprite Coordinates[edit | edit source]

In BASIC all sprites are centered on the coordinate specified, this might produce some counterintuitive effects when using different size sprites, for example if you want to align the sprite edge with the top left side of the screen you would need different values depending on the sprite size

SPRITE 0 IMAGE 1 TO 4,4: REM "8x8 Sprite"
SPRITE 1 IMAGE 1 TO 8,8: REM "16x16 Sprite"
SPRITE 2 IMAGE 2 TO 12,12: REM "24x24 Sprite"
SPRITE 3 IMAGE 3 TO 16,16: REM "32x32 Sprite"

Also, please note that you need to use the command SPRITE X IMAGE Y before setting the sprite coordinates or else BASIC will not know what size is the sprite, and will misalign it, for example the following code although it seems correct will misalign the sprite:

SPRITE 1 TO 8,8
SPRITE 1 IMAGE 1: REM "USe a 16x16 Sprite"