I have a program which includes lots of header files but it do not uses all the header files. I have removed some of them although it is working fine. I did not notice any changes in the performance. 
Will this affect code size or something else. 
Can I include header files as much as I want without affecting the code size and performance.  

I mean if I include all headers in a separate header file then I call only this header file in my all programs. Will it work normally?