What is the purpose of the keyword typedef?

The expression appearing on right side of the assignment operator is called as rvalue. Rvalue is assigned to lvalue, which appears on left side of the assignment operator. The lvalue should designate to a variable not a constant.

The parameters sent to the function at calling end are called as actual parameters while at the receiving of the function definition called as formal parameters.

Yes, it can be but cannot be executed, as the execution requires main() function definition.

When we do not know what type of the memory address the pointer variable is going to hold, then we declare a void pointer for such.

A structure containing an element of another structure as its member is referred so.

Declaration associates type to the variable whereas definition gives the value to the variable.

A structure containing the same structure pointer variable as its element is called as self-referential structure.

No, the header file only declares function. The definition is in library which is linked by the linker.

Dividing the program in to sub programs (modules/function) to achieve the given task is modular approach. More generic functions definition gives the ability to re-use the functions, such as built-in library functions.