#include <iostream>
using namespace std;
struct bitfield
{
unsigned char a : 3, b : 3;
};
int main()
{
bitfield bf;
bf.a = 7;
cout << bf.a;
char c;
cin >> c;
return 0;
}
I am using VC++ with its latest compiler. When i type cast bf.a to int it gives the desired output (7). But when i dont type cast it, it gives no output and gives no errors. Why is it so?
You are printing the character who's value is 7. Others have pointed out that this is a special character that is usually not displayed. Cast your value to int or another non-char integer type to display the value, rather than the character. Go look at the ascii table and you'll see character 7 is BEL (bell).
#include <iostream>
using namespace std;
struct bitfield
{
unsigned char a : 3, b : 3;
};
int main()
{
bitfield bf;
bf.a = 7;
cout << (int)bf.a; // Added (int) here
char c;
cin >> c;
return 0;
}
Edit 1: Since bf.a is only 3 bits, it cannot be set to any displayable character values. If you increase it's size, you can display characters. Setting it to 46 gives the period character.
#include <iostream>
using namespace std;
struct bitfield
{
unsigned char a : 6, b : 2;
};
int main()
{
bitfield bf;
bf.a = 46;
cout << bf.a;
char c;
cin >> c;
return 0;
}
Edit 2: See This answer about using bitfields and char.
When i type cast bf.a to int it gives the desired output (7). But when i dont type cast it, it gives no output and gives no errors. Why is it so?
The character (number 7) was written to the console. Character 7 is the bell character.
So you can't see it, but you can hear it. Or rather I could hear the notification sound on Windows 10 when I ran the program.
The same output is generated with:
cout << '\a';
The bell is part of a group of characters that can be referenced with escape sequences.
Note that in this case the use of a char bitfield is not guaranteed by the standard. See here for a question regarding the use of char bitfields.
Char type bitfield is not supported.
Bitfield declaration supports only 4 identifiers,
