programs produces different results in C and C++

There can be many such programs, following are some of them.

1) 

Character literals are treated differently in C and C++. In C character literals like ‘a’, ‘b’, ..etc are treated as integers, while as characters in C++.

For example, the following program produces sizeof(int) as output in C, but sizeof(char) in C++.

#include<stdio.h> int main() {   printf("%d", sizeof('a'));   return 0; }

2)

 In C, we need to use struct tag whenever we declare a struct variable. In C++, the struct tag is not necessary. For example, let there be a structure for Student. In C, we must use ‘struct Student‘ for Student variables. In C++, we can omit struct and use ‘Student‘ only.

Following is a program that is based on the fact and produces different outputs in C and C++. It prints sizeof(int) in C and sizeof(struct T) in C++.

#include <stdio.h> int T;    int main() {     struct T { double x; };  // In C++, this T hides the global variable T,                             // but not in C     printf("%d", sizeof(T));     return 0; }

3) Types of boolean results are different in C and C++. .

// output = 4 in C (which is size of int) printf("%d", sizeof(1==1));   // output = 1 in c++ (which is the size of boolean datatype) cout << sizeof(1==1);