Zip format distribution of Decimal BASIC includes SETUP.BAT and UNSETUP.BAT.
SETUP.BAT registers BASIC in the start menu, asking whether the shortcut should be made on the desktop, associates the extension ".BAS" to BASIC.EXE.
If it was run with administrative privileges, it makes BASIC.EXE save option settings in the Windows registry,
UNSETUP.BAT removes the settings made by SETUP.BAT.
The setting of using the registry is recorded on BASIC.INI.
If BASIC.INI was deleted by mistake, launch SETUP.BAT again.
SETUP.BAT registers two actions of "Edit" and "Run".
In case of "Edit", when BASIC.EXE is launched by association, it starts with the file open.
In case of "Run", when BASIC.EXE is launched by association, it runs the program and then terminates.
The action that is defined by double-clicking a file with an extension ".BAS" is "Edit".
If this differs from your desire, use the registry editor,
search the key BAS_file\shell in the foldersC
and then Rename Edit key to XEdit or so, which starts with a letter following R.