About the SDK archives The rare and elusive ZBasic (v4.20) basic program language for the Apple II computers (128k models) with complete text files; documentation, full commands HELP lists and the XREF DOCS plus the ZBasic cross-reference utility have been made available for public access and download in both 3.5 disk and 5.25 disk - ShrinkIt disk archive file formats (SDK). The ZBasic.3.5.SDK archive file is a 3.5 ProDOS boot, program and samples disk that contains all same files as both the ZBasic.525A.SDK and ZBasic.525B.SDK archives. The ZBasic.525A.SDK archive is a 140 ProDOS boot/program disk. The ZBasic.525B.SDK is a 140 ProDOS data disk of samples and the cross-ref. XREF ZBasic utility program. All the text files in this folder are also on both the 3.5 archive and the 5.25 disk archives. Apple II Forever, MacProber