Is it optional to use struct keyword before declaring a structure object?

Question

To declare a class object we need the format

classname objectname;

Is it the sameway to declare a structure object?

like

Answer 1

This is one of the differences between C and C++.

In C++, when you define a class you can use the type name with or without the keyword class (or struct).

// Define a class.
class A { int x; };

// Define a class (yes, a class, in C++ a struct is a kind of class).
struct B { int x; };

// You can use class / struct.
class A a;
struct B b;

// You can leave that out, too.
A a2;
B b2;

// You can define a function with the same name.
void A() { puts("Hello, world."); }

// And still define an object.
class A a3;

In C, the situation is different. Classes do not exist, instead, there are structures. You can, however, use typedefs.

// Define a structure.
struct A { int x; };

// Okay.
struct A a;

// Error!
A a2;

// Make a typedef...
typedef struct A A;

// OK, a typedef exists.
A a3;

It is not uncommon to encounter structures with the same names as functions or variables. For example, the stat() function in POSIX takes a struct stat * as an argument.