Editing Commodore BASIC (section)

==Use as user interface==
In common with other [[home computer]]s, Commodore's machines booted directly into the BASIC interpreter. BASIC's file and programming commands could be entered in [[direct mode]] to load and execute software. If program execution was halted using the RUN/STOP key, variable values would be preserved in RAM and could be PRINTed for debugging. The 128 even dedicated its second 64k bank to variable storage, allowing values to persist until a <code>NEW</code> or <code>RUN</code> command was issued. This, along with the advanced [[screen editor]] included with Commodore BASIC gave the programming environment a [[REPL]]-like feel; programmers could insert and edit program lines at any screen location, interactively building the program.<ref>{{cite book|url=https://books.google.com/books?id=UbvzBwAAQBAJ&pg=PA9|title=An Introduction to the Commodore 64: Adventures in Programming |isbn=9781489967879 |last1=Scrimshaw |first1=N. B. |date=11 November 2013 |publisher=Birkhäuser }}</ref> This is in contrast to business-oriented operating systems of the time like [[CP/M]] or [[MS-DOS]], which typically booted into a [[command-line interface]]. If a programming language was required on these platforms, it had to be loaded separately.

While some versions of Commodore BASIC included disk-specific <code>DLOAD</code> and <code>DSAVE</code> commands, the version built into the [[Commodore 64]] lacked these, requiring the user to specify the disk drive's device number (typically 8 or 9) to the standard <code>LOAD</code> command, which otherwise defaulted to tape. Another omission from the Commodore 64s BASIC 2.0 was a <code>DIRECTORY</code> command to display a disk's contents without clearing main memory. On the 64, viewing files on a disk was implemented as loading a "program" which when listed showed the directory as a pseudo BASIC program, with the file's block size as the line number. This had the effect of overwriting the currently loaded program. Addons like the DOS Wedge overcame this by rendering the directory listing direct to screen memory.