SuperBASIC

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

• SuperBASIC Reference Manual.
• SuperBASIC Memory Map
• Watch EMWhite's excellent intro series on YouTube: Full Playlist.

An informal list of tips, "gotchas":

IF, THEN, ELSE

Source of this tip: Ernesto

• 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

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

• 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

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

• 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

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

Code	Effect
chr$(12)	Clear screen and set cursor to upper left corner
chr$(16)	Cursor up
chr$(14)	Cursor down
chr$(2)	Cursor left
chr$(6)	Cursor right
chr$(1)	Set cursor to leftmost position in current line
chr$(5)	Set cursor to righmost position in current line
chr$(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

• 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

Memcopy lockup

• 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

• mlcopy github page

Sprite Images

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

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 an SPRITE X IMAGE Y before moving the sprite or else BASIC will not know what size is the IMAGE of the sprite and will misalign it, for example this following code might misalign an sprite:

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