Friday, 20 June 2014

programs produces different results in C and C++

There can be many such programs, following are some of them.
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++.
int main()
  printf("%d", sizeof('a'));
  return 0;
 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);

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