C Programming Interview Question Part I

Que 1.	What is an lvalue?
Ans.	An lvalue is an expression to which a value can be assigned. The lvalue expression is located on the left side of an assignment statement, whereas an rvalue is located on the right side of an assignment statement. Each assignment statement must have an lvalue and an rvalue. The lvalue expression must reference a storable variable in memory. It cannot be a constant. For instance, the following lines show a few examples of lvalues:
	int x; int* p_int; x = 1; *p_int = 5;
	The variable x is an integer, which is a storable location in memory. Therefore, the statement x = 1 qualifies x to be an lvalue. 1 = x Here compiler generate the error because the left value is contact which cannot be assigned.
Que 2.	What is an rvalue?
Ans.	rvalue can be defined as an expression that can be assigned to an lvalue. The rvalue appears on the right side of an assignment statement. Unlike an lvalue, an rvalue can be a constant or an expression, as shown here:
	int x, y; x = 1; /* 1 is an rvalue; x is an lvalue */ y = (x + 1); /* (x + 1) is an rvalue; y is an lvalue */
	An assignment statement must have both an lvalue and an rvalue.Therefore, the following statement would not compile because it is missing an rvalue:  int x;  x = void_function_call() /* the function void_function_call() returns nothing */ If the function had returned an integer, it would be considered an rvalue because it evaluates into something that the lvalue, x, can store.
Que 3.	What are enumerations?
Ans.	They are a list of named integer-valued constants. Example:       enum color { black , orange=4,yellow, green, blue, violet }; This declaration defines the symbols “black”, “orange”, “yellow”, etc. to have the values “1,” “4,” “5,” … etc. The difference between an enumeration and a macro is that the enum actually declares a type, and therefore can be type checked.
Que 4.	What are register variables? What are the advantages of using register variables?
Ans.	If a variable is declared with a register storage class, it is known as register variable. The register variable is stored in the cpu register instead of main memory. Frequently used variables are declared as register variable as it’s access time is faster.
	For Eg. register int x=90;
Que 5.	What do you know about Storage classes?
Ans.	A storage class defines the scope (visibility) and life time of variables and/or functions within a C Program. There are following storage classes which can be used in a C Program
	auto register static extern