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@ -131,37 +131,48 @@ Data Types
IL65 supports the following data types:
| type | size | type identifier | example |
|--------------------|------------|-----------------|---------------------------------------------------|
| (unsigned) byte | 8 bits | ``.byte`` | ``$8f`` |
| (unsigned) integer | 16 bits | ``.word`` | ``$8fee`` |
| boolean | 1 byte | | ``true``, ``false`` (aliases for the numeric values 1 and 0) |
| character | 1 byte | | ``'@'`` (converted to a numeric byte) |
| floating-point | 40 bits | ``.float`` | ``1.2345`` (stored in 5-byte cbm MFLPT format) |
| string | variable | ``.text``, ``.stext`` | ``"hello."`` (implicitly terminated by a 0-byte) |
| pascal-string | variable | ``.ptext``, ``.pstext`` | ``"hello."`` (implicit first byte = length, no 0-byte |
| address-of | 16 bits | | ``#variable`` |
| indirect | variable | | ``[ address ]`` |
| type | storage size | type identifier | example |
|-------------------------|-------------------|-----------------|---------------------------------------------------|
| unsigned byte | 1 byte = 8 bits | ``.byte`` | ``$8f`` |
| unsigned word | 2 bytes = 16 bits | ``.word`` | ``$8fee`` |
| floating-point | 5 bytes = 40 bits | ``.float`` | ``1.2345`` (stored in 5-byte cbm MFLPT format) |
| byte array | varies | ``.array`` | @todo |
| word array | varies | ``.wordarray`` | @todo |
| matrix (of bytes) | varies | ``.matrix`` | @todo |
| string (petscii) | varies | ``.text`` | ``"hello."`` (implicitly terminated by a 0-byte) |
| pascal-string (petscii) | varies | ``.ptext`` | ``"hello."`` (implicit first byte = length, no 0-byte |
| string (screencodes) | varies | ``.stext`` | ``"hello."`` (implicitly terminated by a 0-byte) |
| pascal-string (scr) | varies | ``.pstext`` | ``"hello."`` (implicit first byte = length, no 0-byte |
Strings can be writen in your code as CBM PETSCII or as C-64 screencode variants,
these will be translated by the compiler. PETSCII is the default, if you need screencodes you
have to use the ``s`` variants of the type identifier.
If you write a string with just one character in it, it is *always* considered to be a BYTE instead with
that character's PETSCII value. So if you really need a string of length 1 you must declare it
explicitly as a variable of type ``.text``, you cannot put ``"x"`` as a subroutine argument where
the subroutine expects (the address of) a string. IL65's type system is unfortunately not strict enough to
avoid this mistake, but it does print a warning if the situation is detected.
For many floating point operations, the compiler has to use routines in the C-64 BASIC and KERNAL ROMs.
So they will only work if the BASIC ROM (and KERNAL ROM) are banked in, and your code imports the ``c654lib.ill``.
You can use the literals ``true`` and ``false`` as 'boolean' values, they are aliases for the
byte value 1 and 0 respectively.
Strings in your code will be encoded in either CBM PETSCII or C-64 screencode variants,
this encoding is done by the compiler. PETSCII is the default, if you need screencodes you
have to use the ``s`` variants of the string type identifier.
A string with just one character in it is considered to be a BYTE instead with
that character's PETSCII value. So if you really need a string of length 1 you must declare
the variable explicitly of type ``.text``.
Floating point numbers are stored in the 5-byte 'MFLPT' format that is used on CBM machines,
but most float operations are specific to the Commodore-64 even because
routines in the C-64 BASIC and KERNAL ROMs are used.
So floating point operations will only work if the C-64 BASIC ROM (and KERNAL ROM) are banked in, and your code imports the ``c654lib.ill``.
The largest 5-byte MFLPT float that can be stored is: 1.7014118345e+38 (negative: -1.7014118345e+38)
Indirect addressing and address-of
----------------------------------
**Address-of:**
The ``#`` prefix is used to take the address of something. This is sometimes useful,
for instance when you want to manipulate the *address* of a memory mapped variable rather than
the value it represents. You can take the address of a string as well, but the compiler already
treats those as a value that you manipulate via its address, so the ``#`` is ignored here.
For most other types this prefix is not supported.
the value it represents. You could take the address of a string as well, but that is redundant:
the compiler already treats those as a value that you manipulate via its address.
For most other types this prefix is not supported and will result in a compile error.
The resulting value is simply a 16 bit word.
**Indirect addressing:** The ``[address]`` syntax means: the contents of the memory at address, or "indirect addressing".
By default, if not otherwise known, a single byte is assumed. You can add the ``.byte`` or ``.word`` or ``.float``
@ -261,7 +272,7 @@ If you do modify them in-place, you should take care yourself that they work as
expected when the program is restarted.
### Blocks
### Blocks and Scopes
~ blockname [address] {
[directives...]
@ -273,17 +284,21 @@ arranged to a single output program. No code or data can occur outside a block.
A block is also a *scope* in your program so the symbols in the block don't clash with
symbols of the same name defined elsewhere. You can refer to the symbols in a particular block
by using a *dotted name*: ``blockname.symbolname``.
Note that the *file* (or module) that blocks are defined in, is of no consequence to the
full scope name; all blocks defined in it are simply added to the set of blocks that make up the
entire program.
Block names must be unique in your entire program,
except "ZP": the contents of every block with that name are merged into one.
This block name refers to the zero page. Its start address is always set to $04,
Hence block names must be unique in your entire program.
Except "ZP": the contents of every block with that name are merged into one.
This "ZP" block name is special and refers to the zero page. Its start address is always set to $04,
because $00/$01 are used by the hardware and $02/$03 are reserved as general purpose scratch registers.
Block address must be >= $0200 (because $00-$fff is the ZP and $100-$200 is the cpu stack)
You can omit the blockname but then you can only refer to the contents of the block via its absolute address,
which is required in this case. If you omit *both*, the block is ignored altogether (and a warning is displayed).
When declaring a block in your code, it's possible to omit the blockname.
But then you can only refer to the contents of the block via its absolute address,
which is required in this case. If you omit *both* name and address, the block is *ignored* by the compiler (and a warning is displayed).
This is a way to quickly "comment out" a piece of code that is unfinshed or may contain errors that you
want to work on later, because the contents of the ignored block are not fully parsed.
want to work on later, because the contents of the ignored block are not fully parsed either.
### Assignments
@ -340,9 +355,9 @@ The syntax is:
what the changed registers are, assume the worst")
Subroutines that are pre-defined on a specific memory location (usually routines from ROM),
can also be defined using the 'sub' statement. But in this case you don't supply a block with statements,
but instead assign a memory address to it:
Pre-defined subroutines that are available on specific memory addresses
(in system ROM for instance) can also be defined using the 'sub' statement.
To do this you assign the routine's memory address to the sub:
sub <identifier> ([proc_parameters]) -> ([proc_results]) = <address>