Which of the following is not a form of memory?

The optimal page replacement algorithm will select the page that.

In the index allocation scheme of blocks to a file, the maximum possible size of the file depends on

Which combination of the following features will suffice to characterize an $$OS$$ as a multi-programmed $$OS?$$
$$(a).$$ More than one program may be loaded into main memory at the same time for execution.
$$(b).$$ If a program waits for certain events such as $$I/O$$, another program is immediately scheduled for execution.
$$(c).$$ If the execution of a program terminates, another program is immediately scheduled for execution.