39 Indirection operators 378 40 HIMEM, LOMEM, TOP and PAGE 383 41 Operating system statements 385 42 The shadow screen 387 Other shadow mode-related commands 388 43 The operating system and how to make use of it 389 What is the operating system?
389 The *FX commands 390 OSBYTE calls from BASIC 391 OSBYTE calls from assembly language 393 The *FX commands and OSBYTE calls 395 Functional summary (alphabetical) 396 Numerical summary 398 44 An introduction to assembly language 428 Machine code and the assembler 428 Uses of assembly language 429 The main features of 6502 assembly language 429 The 6512 registers 430 Program counter 430 Accumulator 430 X register 430 Y register 430 Program status register 431 Stack pointer 431 The assembler delimiters ‘[’ and ‘]’, and general assembly language syntax rules 431 Addressing modes 432 Implicit addressing 432 Immediate addressing and zero page addressing 432 Absolute addressing 433 Indirect addressing 433 Indexed addressing 433 Relative addressing 435 Accumulator addressing 436 Placing machine code programs in memory 436 OPT, forward referencing and two-pass assembly 438 The EQUate facility 439 Machine code entry points 441