Declaration and Initialization ( Part2 )

Declaration and Initialization (C-FAQ's)

Q1: Differences between a Declaration and a Definition ?

            When we define a variable, a space is reserved for the variable and it also got some default value. But declaration only identifies the type of a variable.

               

                Redefinition is an error. But re-declaration is not an error.

               

                Example:-

                        extern int iNum;

                        float fVar;

                                    Here extern int iNum is a declaration and float fVar is definition.

 

Q2: Can you identify which of the following are declarations and definition ?

          extern int iNum;

            double dVar;

            void vFunc(int, float);

            int getVar() {}

            Output:        

                        extern int iNum       is a declaration

                        double dVar             is a definition

                        void vFunc(int, float)        is a declaration

                        int getVar() {}          is definition

Q3: Will the following code compile fine. If it is what will be the output ?

          #include<stdio.h>

            int main()

            {

                        extern int iNum;

                        printf("%d\n",iNum);

                        return 0;

            }

            int iNum=30;

 

            Output:        

                                There is no error in the above code, this will compile fine.

                        It prints 30.

Q4: What is the output of the following code?

          #include<stdio.h>

            int main()

            {

                        extern float fNum;

                        printf("%f\n",fNum);

                        return 0;

            }

           

            Output:        

                                Compiler will return an error "Undefined fNum". Because extern float fNum is a declaration not a definition.

<< PREV               [C FAQ's]            NEXT >>