Data types: int and pointers are 16-bit; long and float are 32-bit. double and long long (64-bit or more) are unsupported. Structs/unions: Passing/returning by value and bit fields are implemented. Function parameters: Only the first parameter is passed via registers (A/B/@long). If the first parameter is a struct/union, all parameters are passed via the stack. Return values: Struct/union return values pass their address as an implicit first argument in a register. all other normal arguments are passed on the stack.