The C header files are in the same place as other Unix and Unix-like systems:
/usr/include
if you installed the compiler.
It's 1405 in my Linux box.
Java does not require header files like C/C++.
C programs do not require header files. If you want a C program without header files, you can simply not create them. However, you may or may not be able to include your non-header file source files.
list of header files in c and function prototype associated with each file
It isn't necessary to include header files in C. However, without the functionality provided by some header files, your program wouldn't be able to do very much that is useful.
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Yes.
No predefined 'header' function in the standard C libraries. There are header files, if that's what you mean.
No.
The need to declare header files is not compulsory in C++. You may place all your code in a single source file if you so desire. However, header files are useful in that they separate interface from implementation and aid in hiding information.
to include the header files.
For start: they are header files.