single level directory

two level directory

tree structure

all of these

uses more tapes

should be done each month

saves only files that have recently changed

saves all files

single level directory

two level directory

tree structure directory

none of these

is needed by every installation

is never needed

varies in degree between installations

requires off-site computer for immediate use

text files

executable binary flies

both 1) text files and 2) executable binary flies

none of these