In a pgm,if the input is a single line or several lines,what is the
statement i have to give.I have to get the input as a whole.

I _suggest_ that you mean the following:

You have a program which works on standard input. No matter whether
this standard input consists of no input, one single line, or many
lines of input, you have to process this input as a whole.

Is my understanding correct?

If so, in C you might want to use fread() in a loop until feof() is true:


Within this loop, append the current buffer content to the whole input
that you've read so far.
Before doing so, you should check whether the piece of memory you have
allocated for the whole input is large enough to hold the current
contents of "myBuffer"; if not, you will have to reallocate this
memory or react in some other useful way (for example, terminate the
program after printing an error message).