With reference to system building, explain why you may sometimes have to maintain obsolete computers on which large software systems were developed.

What will be an ideal response?

Obsolete computers may have to be maintained if the software used to build the
system (compiler, linker, etc.) is not available for newer hardware. This situation
can arise of the compiler vendor has gone out of business and no-one else is
supporting their system. It may not be possible to use a compiler on a newer system
as the code produced may be different. It can also arise when programs are
developed in a programming language that is no longer used – it may be cheaper to
maintain the obsolete hardware to run the compiler than to buy a new compiler for
occasional use.