command line input in c

How can command line input be obtained in c?
please give your answer in the following scenario ….

You are given a program that has to accept input from an input1.txt file. This file contains some strings that U have to reverse….

Once u r done U make an exe file of your program and it is executed in this fashion…

c:\tc\bin>program1 input1.txt

Please give me a suitable answer
Thanx