Minor Differences Between C and C++

  There are some major differences between C and C++. You can refer a good C++ programming text book to find those differences. Here in this post I am discussing about a few subtle differences between C and C++. I have tried to include as many points as possible, but still there might be some points missing.

• In C by default the return type of a function is integer. But this rule is not valid in C++. You have to mention the return type as integer explicitly. 

                               add( )  // Valid in C.
                               add( )  // Error in C++.

• In C an empty function prototype tells the compiler that the function can have any number of arguments. But in C++ it means the function does not take any argument.

                               int add( );  // in C this function can take any number of arguments.
                               int add( );  // in C++ this function does not take any arguments.  

• Structure variable declaration is different for C and C++. Consider the structure given below. 

                              struct sample
                              {
                                  int x,y;
                              };
          In C structure variable is declared as follows.
                             struct sample var1;
          In C++ structure variable is declared as follows.                               
                             sample var1;

• Built-in memory-handling operators new and delete are available in C++. In C dynamic memory allocation is done with the help of functions malloc( ) and free( ).

• Single line comment ( // ) is available in C++.

• Address of register variable can be taken in C++. But in C it is not possible.

• Size of enumeration constant is that of integere in C. But in C++ size of enumeration variable is not fixed. It depends on the size requirement of the enumeration constant.

• Anonymous unions can be declared in C++.

• Anonymous enumeration is possible in C++ if just enumeration constants are required.

• C++ preprocesser provides an additional predefined macro constant __cplusplus.

• The unary increment and decrement operators in C++ returns an lvalue. But in C they return an rvalue.

                            (++i)++;  // Error in C, but in C++ it is valid.
                            ++i=0;    // Error in C, but in C++ it is valid.