fp = fopen("D:/abc.txt","r");
should be
fp = fopen("D:\\abc.txt","r");
in use \
in path instead of /
in Windows and extra \
for escape sequence.
EDIT:
As you commented to others answers that fp = fopen("D:\\abc.txt","r");
also not working then check what is name actually. You might given probably wrong name by mistake, check whether you have error like this.
(1) open command prompt
(2) use DIR command to print name of file:
c:\Users\name> D:
D:\> DIR
Volume in drive D is FUN BOX
Volume Serial Number is B48A-3CE7
Directory of d:\
27-02-2013 19:23 0 abc.txt.txt
26-02-2013 22:05 <DIR> BOLLYWOOD MOVIES
27-02-2013 19:31 0 x
2 File(s) 0 bytes
1 Dir(s) 11,138,654,208 bytes free
file name is abc.txt.txt
but when you see this in folder extension doesn't appears and file name looks abc.txt
I am Linux user and I normally do this mistake in Windows. That's why. May be it help you!