Qbasic Compiler -

t1 = x + 3 t2 = t1 * 2 PRINT t2 Targets three possible back-ends:

Design and Implementation Considerations for a QBASIC Compiler: Bridging Legacy Interpreters and Modern Execution Environments qbasic compiler

This paper provides a comprehensive blueprint for anyone attempting to build or understand a QBASIC compiler. t1 = x + 3 t2 = t1

# Input: test.bas # 10 PRINT "Hello" # 20 END tokens = lexer("test.bas") ast = parser(tokens) ast.resolve_labels() # line 10 -> label_L10 ir = gen_ir(ast) asm = gen_x86(ir) write_exe(asm) | Compiler | Backend | QBASIC Compatibility |

Observation: Compilation yields ~20-60x speedup. Overhead in QB64 results from graphics/compatibility layer. | Compiler | Backend | QBASIC Compatibility | Notable Feature | | :--- | :--- | :--- | :--- | | QB64 | C++ (GCC/LLVM) | High (syntax, graphics) | Emulates QBASIC’s _MEM and OpenGL | | FreeBASIC | GNU as / C | Partial (more QB 4.5) | Supports 64-bit and pointers | | QBASIC Compiler (QB71) | Custom ASM | Very high | Produces small .COM files for DOS |