Opencv – Error when compiling cv.h: No such file or directory

When I compile a simple program : hello_world.cpp

**I get the error-
**fatal error: cv.h: No such file or directory
compilation terminated.****

Solutions I found but didn't work:

1. I checked for cv.h and highgui.h if they are there, and got these results:
   /home/snu/OpenCV-2.4.0/include/opencv/highgui.h
   /usr/lib/perl/5.14.2/CORE/cv.h
   /home/snu/OpenCV-2.4.0/include/opencv/cv.h

2. I checked if opencv is correctly installed by using
   pkg-config opencv –libs, this is what i got :
   -lopencv_calib3d -lopencv_imgproc -lopencv_contrib -lopencv_legacy -lopencv_core -lopencv_ml -lopencv_features2d -lopencv_objdetect -lopencv_flann -lopencv_video -lopencv_highgui

3. I made some changes in the header files of hello_world.cpp as-
   #include "opencv2/highgui/highgui.hpp"