What is exact meaning Windows NT 3.51 title bar buttons? Arrow up is maximize and arrow down minimize? And left button is close? Its my assumption right?
The upward-pointing arrow does indeed maximise the window, and the downward-pointing arrow minimises it.
The “minus” provides access to the window menu; double-clicking it will close the window. The menu for an application window is this:
The menu for an MDI document window (such as a program group in Program Manager) is this:
Applications can add their own entries to these menus.
These exact buttons were used in Windows 3.0, Windows 3.1 (and variants), Windows NT 3.1, Windows NT 3.51, and OS/2 1.3. I think the two menu buttons are supposed to be reminiscent of their keyboard short-cuts, AltSpacebar and Alt-.
2I always interpreted the symbol on the left-hand button as a handle (like on a filing-cabinet drawer) that you'd pull on to reveal the menu (ok, at that point the metaphor collapses). May 28, 2020 at 12:00
Ah yes, I can see that; I always thought of them as “spacebar” and “minus” (because of the corresponding short-cuts, Alt+Spacebar and Alt+-). May 28, 2020 at 12:08
Unfortunately, I don't have a link, but I remember Raymond Chen (or one of the other Microsoft bloggers he linked to) treating the "meant to be a spacebar" interpretation for application windows as unarguably correct. (It stuck in my mind because it was such a "Huh. I never thought of it that way." moment.)– ssokolowMay 28, 2020 at 12:56
1Jensen Harris wrote about the space bar/hyphen connection in 2006: docs.microsoft.com/en-us/archive/blogs/jensenh/… May 28, 2020 at 17:33
4The system menu(s) still exists; the icon has been replaced by the application-specific icons since Windows 95. Some applications might omit the icon entirely but the menu can usually still be accessed (unless directly suppressed by the application) using the same keystrokes. May 28, 2020 at 19:08