save and regerate the current screen before and after a command

[Guy Harris]

>no, but it does switch to and use the alternate screen, thus
>preserving the terminal's previous contents.  At least that what it
>does for me...

Probably because you're using a terminal, or a terminal emulator, that
*has* an alternate screen; not all do.  "xterm" does; Sun "shelltool"
doesn't; Sun "cmdtool" has something that, in some circumstances, acts
like one (the "ti" and "te" capabilities switch a "cmdtool" from
"cmdtool mode" to "shelltool mode", or from "shelltool mode" to "cmdtool
mode", respectively, and those modes have independent screen images).