Keeping Deleted Code for Future Reference (with comments)

Many a times we have come across a situation where we want to
keep a piece of code that does not execute. If often do it with "/*" and
"*/". But these won't work if there are similar comments within the
piece of code we want to comment. It achieve this use "#if 0" and
"

eg:

#if 0

/* Used for debugging */
while (a < n)

printf ("%d", a);

#endif