What is a preprocessor?

Can be used to input integer in all the supported format.

Escape it using (backslash).

Yes, if it is not appearing as the last case and if we do not want the control to flow to the following case after default if any.

If the structure/union variable is a pointer variable, to access structure/union elements the arrow operator is used.

We can create integer structure members of differing size apart from non-standard size using bit fields. Such structure size is automatically adjusted with the multiple of integer size of the machine.

The arguments which we pass to the main() function while executing the program are called as command line arguments. The parameters are always strings held in the second argument (below in args) of the function which is array of character pointers. First argument represents the count of arguments (below in count) and updated automatically by operating system.

It compares two strings by ignoring the case.

Opens a file both for reading and writing. If a file is not existing it creates one, else if the file is existing it will be over written.

It cannot be used on constants. It cannot be used on variable which are declared using register storage class.