AQB: A BASIC Compiler and IDE for Amiga Computers

About

• Project Scope
• Requirements
• Installation
• Benchmark Results
• Source Code
• Authors

Command Reference

• Reference: Core
• Reference: Amiga specific commands
• Reference: IFFSupport
• Reference: AnimSupport

AQB Programming Language

• Type System
• Module System and Runtime
• Code Generation and Target Systems
• Interrupting / break handling in AQB programs

Amiga OS System Programming in AQB

• Introduction
• Reference: OSUtility

IDE

• Keyboard shortcuts

Project Scope

An experiment in alternate history: what AmigaBASIC could have looked like, had it been developed further tailored to the Amiga OS.

What AQB is not: AQB does not try to be a clone of any particular BASIC dialect - neither QuickBASIC, FreeBASIC or VisualBASIC nor any particular Amiga specific BASIC implementation like AmigaBASIC, ACE, HiSoft, GFA, Blitz or AMOS. While it strives to be as compatible as possible with the Microsoft BASIC family of languages (and certainly has many QuickBASIC traits) the primary focus is on the creation of a modern, clean, Amiga OS-compliant, future-proof BASIC that is tailored towards modern Amiga application development.

To be more specific, FreeBASIC is the source of many core AQB language constructs (in many respects AQB can be considered a subset of FreeBASIC) with inspiration for Amiga specific commands mainly from AmigaBASIC, ACE and HiSoft. Main target is Amiga OS compliant application development.

Improvements over AmigaBASIC include:

• Advanced type system (including UDTs and Pointers, see below)
• Support for non-static functions and subs (enables recursion)
• Module support (similar to UNITs in TurboPascal, with full type safety and dependencies)
• Modern syntax inspired by FreeBASIC and VisualBASIC
• True native 68k compiler
• Integrated IDE besides compiler command line interface with
  • syntax highlighting
  • auto-indent
  • folding support
  • source level debugging

Requirements

• 3 MB RAM
• OS 3.1 (V39) or newer

Installation

Download a release LHA archive (https://github.com/gooofy/aqb/releases) and unpack it wherever you like, keep the directory structure intact.

AQB should run from this point on without the need for further installation, but for convenience add a "AQB:" assign to your S:user-startup file, e.g.

;BEGIN AQB
Assign AQB: "sys:Apps/AQB"
;END AQB

Type System

Basic types:

• Byte, UByte (8 bits)
• Integer, UInteger (16 bits)
• Long, ULong (32 bits)
• Single (32 Bit FFP floats)
• Boolean (8 bits)

Advanced types

• Static (C-like, fast) and dynamic (runtime bounds checking) arrays
• UDTs (structs)
• OOP (FreeBASIC like)
• Pointers (C-like, including function/sub pointers)
• Strings (0-terminated pointers to UByte, C-compatible)

Module System and Runtime

AQB tries to keep the set of commands that are built into the compiler to a minimum and relies on its quite powerful module system to provide most of the commands as part of the runtime system. This means that while the default runtime strives to implement a modern QuickBASIC like dialect tailored to the Amiga, it is quite possible to implement alternative runtime modules that could provide AQB with a different "personality", e.g. one that is closer to AmigaBASIC or GFA BASIC or even languages like BlitzBasic or AMOS.

The goal for AQB's default runtime is to provide a rich set of commands covering typical Amiga OS programming topics like GUI programming, multitasking, graphics and audio combined with resource tracking and error/exception handling. Future plans might also include an automated garbage collector to make memory allocation easier and safer.

AQB is fully link-compatible with the Amiga 68k GCC compiler which means that AQB modules can be implemented in C as well as BASIC (one could even mix these languages within one module, i.e. implement some subprograms in C while others in BASIC).

Intuition / Exec event handling

Since the default runtime wants to enable OS friendly programming no busy waiting is used. Therefore the SLEEP command is used to process pending events, i.e. you will need to call SLEEP regularly in your program, typically form a main loop that could look like this:

WHILE running
    SLEEP
WEND

For event processing you register subroutines using the ON ... CALL family of statements, e.g.

ON WINDOW CLOSE CALL 1, myWindowHandler

see https://github.com/gooofy/aqb/blob/master/examples/demo/gfx1.bas for a simple example of this approach.

Interesting detail: since AQB supports C-like function pointers, the ON ... CALL family of statements is not built into the compiler but part of the _aqb runtime:

PUBLIC DECLARE SUB ON WINDOW CLOSE CALL (BYVAL wid AS INTEGER, BYVAL p AS SUB (BYVAL INTEGER))

Code Generation and Target Systems

At the time of this writing classic 68k Amiga systems is the only compiler target. The idea is to focus on one target and try to make AQB work really well on this platform before expanding to other systems. The AQB compiler is implemented from scratch in C based on Appel's 1997 book "Modern Compiler Implementation in C" and tries to keep system requirements (RAM and CPU) low while still producing somewhat sensible machine code. Originally the AQB code was based on ComMouses's tiger compiler implementation (https://github.com/ComMouse/tiger-compiler) which provided a very useful starting point.

For future expansions to other platforms the current plan is to use an LLVM based backend for all platforms powerful enough to run LLVM which is probably true for most NG Amiga systems (AROS, AmigaOS 4 and MorphOS) and most likely also for highly expanded classic Amiga systems (using accelerator cards such as PiStom or Vampire).

As for the 68k compiler future plans include further reduction of its memory footprint ideally to a point where it is useful on 1MB or even 512K Amiga systems. At that point it might even make sense to implement a 6502 backend targeting modern 8 bit systems like the MEGA65, Commander X16 or C256 Foenix.

Interrupting / break handling in AQB programs

By default, the runtime will check for break signals in i/o routines. Break signals can be sent either by pressing CTRL-C or by using the AmigaDOS BREAK command.

Additionally, the compiler will insert checks for break signals in all loop statements (to protect against endless loops) and in subprogram startup code (to protect against infinite recursion). This is enabled by default but since this will make code longer and cost some performance, it can be switched off using the

OPTION BREAK OFF

statement.

Amiga OS System Programming in AQB

AQB datatypes are very similar to C (C-like strings, structs and pointers) which makes usage of Amiga OS libraries and devices pretty seamless.

Data structures generally can be modeled 1:1 from their C counterparts, a python script semi-automating the task of converting Amiga C library and device headers to AQB is in the works. Here is a preview of what the resulting AQB declarations typically look like:

[...]

TYPE ViewPort
    AS ViewPort PTR NextViewPort
    AS ColorMap PTR ColorMap
    AS CopList PTR DspIns, SprIns, ClrIns
    AS UCopList PTR UCopIns
    AS INTEGER DWidth, DHeight, DxOffset, DyOffset
    AS UINTEGER Modes
    AS UBYTE SpritePriorities, ExtendedModes
    AS RasInfo PTR RasInfo
END TYPE

TYPE Layer_Info
    AS Layer PTR top_layer, check_lp
    AS ClipRect PTR obs, FreeClipRects
    AS LONG PrivateReserve1, PrivateReserve2
    AS SignalSemaphore Lock
    AS MinList gs_Head
    AS INTEGER PrivateReserve3
    AS VOID PTR PrivateReserve4
    AS UINTEGER Flags
    AS BYTE fatten_count, LockLayersCount
    AS INTEGER PrivateReserve5
    AS VOID PTR BlankHook, LayerInfo_extra
END TYPE

EXTERN GfxBase AS VOID PTR

DECLARE SUB Move (rp AS RastPort PTR, x AS INTEGER, y AS INTEGER) LIB -240 GfxBase (a1, d0, d1)
DECLARE SUB RectFill (rp AS RastPort PTR, xmin AS INTEGER, ymin AS INTEGER, xmax AS INTEGER, ymax AS INTEGER) LIB -306 GfxBase (a1, d0, d1, d2, d3)
DECLARE SUB Draw (rp AS RastPort PTR, x AS INTEGER, y AS INTEGER) LIB -246 GfxBase (a1, d0, d1)
DECLARE SUB SetAPen (rp AS RastPort PTR, pen AS INTEGER) LIB -342 GfxBase (a1, d0)

[...]

Keyboard shortcuts:

* F1        - this help screen
* ESC       - toggle console visibility
* S-UP      - page up
* S-DOWN    - page down
* S-LEFT    - goto start of line
* S-RIGHT   - goto end of line
* Ctrl-Up   - goto top of file
* Ctrl-Down - goto end of file
* Ctrl-Y    - delete line
* F5        - compile & run
* F7        - compile
* F9        - toggle breakpoint
* TAB       - fold or unfold subprograms
* Amiga-F   - find
* Amiga-N   - find next
* Amiga-B   - mark block
* Amiga-X   - cut
* Amiga-C   - copy
* Amiga-V   - paste
* Amiga-O   - open file in editor
* Amiga-S   - save file
* Amiga-Q   - quit (also Ctrl-C)

Benchmark Results

Measured on an A500 configuration (PAL 68000, 3MB RAM) in FS-UAE, Kickstart 1.3

Source Code

https://github.com/gooofy/aqb

Authors

• Günter Bartsch (https://github.com/gooofy) Main Author
• S. Hi (https://github.com/blackborn66) Bugfixes, Runtime improvements, IDE improvements, Documentation, Testing, Feedback