Question:Define Operator, Operand, and Expression in 'C'? 

Operators are symbols which take one or more operands or expressions and perform arithmetic or logical computations.
Operands are variables or expressions which are used in operators to evaluate the expression.
Combination of operands and operators form an expression.

Question:What is use of void data type? 

Void is an empty data type normally used as a return type in C/C++, C#, Java functions/methods to declare that no value will be return by the function.
The another used of void is to declare the pointer in C/C++ where It is not sure what data type is addressed by the pointer.

Question:four type of scope in c: 

Block scope.
Function scope.
File scope.
Program scope.

Question:what is nested structure? 

A structure is a collection of one or more variables, possibly of different data types, grouped together under a single name for convenient handling. Structures can contain other structures as members; in other words, structures can nest.

Question:What is prototype of printf function? 

Prototype of printf function is:
 int printf( const char *format ,…)

Question:What is difference between declaration and definition? 

During declaration we just specify the type and no memory is allocated to the variable. But during the
 definition an initial value is assigned and memory is allocated to the variable.

Question:What is function recursion? 

When a function of body calls the same function then it is called as 'recursive function.'
Example:
Recursion()
{
    printf("Recursion !");
    Recursion();
}

Question:What is use of #pragma inline directive in c language? 

#pragma inline only tells the compiler that source code of program contain inline assembly language code .In c we can write assembly language program with help of asm keyword.

Question:What is the meaning of multilevel pointers in c? 

A pointer is pointer to another pointer which can be pointer to others pointers and so on is known as multilevel pointers. We can have any level of pointers.

Question:Difference between pass by reference and pass by value? 

Pass by reference passes a pointer to the value. This allows the callee to modify the variable directly.Pass by value gives a copy of the value to the callee. This allows the callee to modify the value without modifying the variable. (In other words, the callee simply cannot modify the variable, since it lacks a reference to it.)