C Programming - Declarations and Initializations - Discussion

int i;----is declaration.
int i=0;--is definition.
extern int i;--declaration.

Why because this statement declares that int i is already defined somewhere.

Hey,whetr int i; is declaration or definition.
Dn, extern int i; is declaration or definition

Declaration of a variable/function simply declares that the variable/function exists somewhere in the program but the memory is not allocated for them.

Definition: We define a variable/function, apart from the role of the declaration, it also allocates memory for that variable/function.

Initialization: When we assigned the value of a variable.

Eg.

// This is the only declaration. y is not allocated memory by this statement
extern int y;

// This is both declaration and definition, memory to x is allocated by this statement.
int x;

// This is initialization.
x = 94;

int i=0 is a declaration.

But if we write
extern int i;
Then, it becomes a definition because this extern variable reserves space for 'i' and initializes 'i' to zero.

The answer given is wrong. So,the correct answer will be option B.

What is the difference between the following two declarations of a function myfunction?

a) void myfunction (int a[ ]);
b) void myfunction (int *a);

@Abul Asad.

Both are same, address of a is passed as an argument.
In both cases, function will receive the address of a.
In the case of array a[], address of a[0] will be automatically initialised.

What is the difference between the following two declarations of a function myfunction?

a) void myfunction (int a[ ]);
b) void myfunction (int *a);

Please tell me exact explanation of declaration and definition.

This is a statement I think which is telling the compiler that x is an external variable.

The declaration is "int x;" which is declared anywhere in the program & without "int x;" line "extern int x;" will do nothing with x because this line itself is not a declaration.

Declaration: no memory is used. You can not declare a non user defined data type: "int a" is a definition. But you can declare any user defined data type: "struct mystruct{int a; };" It hasn't use any memory. In this view function prototypes are declarations too. "void myfunction(int a);"

Definition: Memory has been used in code or data segment. "int a;" "struct mystruct myvariable;" void myfunction(int a) {printf("%d",a); }