On 3/1/24, Steve Nickolas <usotsuki(a)buric.co> wrote: IBM did a similar thing in their use of the term "main storage" for what the whole rest of the industry calls "main memory". They felt that "memory" was too anthropomorphic. The term "switch" for command line options is pretty much universal--it's not IBM specific and predates the existence of Microsoft by about two decades. Back in the 1950s when you ran one program at a time on a computer, there were toggle switches on the control panel that could be read by the running program. Combinations of these were in common use to select various options of program behavior. When operating systems came along, you couldn't pass the info to running programs by having the operator physically flip a switch on the console. I remember that IBM DOS/360 had a Job Control Language (JCL) statement "// UPSI" (UPSI = User Program Switch Indicators) that allowed one to set the "switches" as seen by the running user program. When interactive and timesharing systems came along, they supported command line options in place of the original switches. In DEC's operating systems for PDP-8 -10, and -11, these were originally a slash character followed by a single letter or digit. The slash was used because it resembles a toggle switch. Unix was using the slash as a directory separator in pathnames and so they used the hyphen to introduce command options instead. Microsoft's command line interface for the PC was modeled after DEC's RT-11 operating system and used slash for command options. When they implemented Unix-style directory paths, they had to use backslash as the separator because forward slash was already in use. -Paul W.

I always took it to be a semi descriptive joke, like “mouse”, with the sort of flag you wave. At least that’s what I assumed the origin was. Silas

On 3/1/24, Bakul Shah via TUHS <tuhs(a)tuhs.org> wrote: I think the term "flag" for command line options comes from the way that those options are typically implemented in code. The command line options are usually used to set a boolean variable in the program that can be tested to see if the option was present. "Flag" as a synonym for a boolean variable in turn comes from the ordinary English verb "to flag", meaning "to mark or identify" -Paul W.