01 NES BASIC PROGRAMMING GUIDE

Welcome to NES BASIC

A small computer can be a good place to learn programming. You type a line, run it, and see exactly what changes. NES BASIC turns an NES cartridge into that kind of computer: a language, a text editor, a graphics canvas, hardware sprites, sound and a small project library, all running on the emulated NES processor.

8-Bit Impostor provides the host screen, touch controls, controller connections, optional external-keyboard transport and persistent battery files. It does not evaluate BASIC for the cartridge. The same standalone ROM has its own controller keyboard and interpreter. The PDF you are reading is a host document, not an NES program; a physical NES does not display this book.

This is a deliberately small integer BASIC. There are single-letter numeric variables and independent single-letter string variables. There are no arrays, floating-point numbers, ELSE, DATA/READ or ON GOTO. Its limitations are useful to know early: they make your programs easier to plan and your errors easier to fix. The feature matrix in the appendices describes this edition rather than another BASIC dialect.

BASIC, NES PAINT, EDITOR, CALCULATOR, NES SHEETS, BLOCKDROP and ASTRO BLASTER are separate cartridges in NDB SOFTWARE. Opening BASIC does not depend on opening Paint, and their saved projects are not shared. This guide concentrates on BASIC.

You can keep a finished image or sprite visible when a program ends. You can also interrupt a loop, return to editing and run it again. Use explicit SAVE to keep source and artwork before resetting or leaving. Saving a program is different from saving an emulator snapshot; Chapter 12 explains both.