DECLARE [SYSTEM] FUNCTION name AT address [ ( par1 [, par2 [, ... ] ] ) ] RETURN ret [ ON targets ]
   par : name AS type ON register
   par : name AS type ON STACK(width)
   ret : register AS type | STACK(width) AS type
   width: BYTE | WORD | DWORD
   targets : name of targets, separated by comma (,)

The DECLARE FUNCTION is a way to define and call external functions written in machine language and to insert assembly into the sources. The functions defined in this way can be called as if they were an integral part of the language. Once the function has been declared, it will be sufficient to invoke it with one of the following syntaxes:

x = test[ ]

as if it were any ugBASIC function. If desired, parameters can be added. For each it is obviously necessary to indicate how the value will be passed to the function written in machine language.

The ugBASIC compiler allows you to declare functions and procedures that are “system”. What does “system” mean? It means that the machine code resides in a ROM, preloaded at run time and therefore already made available to any program that knows how to call it.

However, since ugBASIC makes available all memory space allowed by the hardware, it is possible that the ROMs have been disabled or otherwise made unreachable. Indicating that you want to call a procedure or a system function, ugBASIC will take care of re-enabling the ROM before executing the request, deactivating it on exit.

To declare a procedure or function to be system, simply use the SYSTEM keyword.

  DECLARE SYSTEM FUNCTION test ON CPC, ZX

See also the following example files:

• extern_example_11.bas

 Dec Fu

• Atari (400/800)
• Atari XL/XE
• Commodore 128 (MOS 8502)
• Commodore 128 (Zilog Z80)
• Commodore 64
• Commodore 64+REU
• TRS-80 Color Computer
• TRS-80 Color Computer 3
• ColecoVision
• Amstrad CPC 664
• Dragon 32
• Dragon 64
• Thomson MO5
• Thomson MO5
• Olivetti Prodest PC128
• Commodore PLUS/4
• SEGA SC-3000
• SEGA SG-1000
• VG-5000
• Commodore VIC-20
• ZX Spectrum 48

If you have encountered a problem using this command, if you think there is a bug or the explanation is unclear, please open an issue for this keyword on GitHub. Thank you!