Boolean data type vs integer data types to represent truth values

Question

What is advantage of using bool data type over integer values as 0 and 1 for true and false values, which will be more efficient to use? And how it will differ in different languages like c and c++?

Answer 1

int was used in C when there was no bool, there is no advantage¹ using an integer type to represent a boolean value in C++ or in modern C:

1. bool is meaningful, int is not:

bool try_something();
int try_something(); // What does this return?

It is common in C to have functioning returning int to indicate success or failure, but a lot (most?) of these do not return 1 on success and 0 on failure, they follow UNIX standard which is to return 0 in case of success and something else in case of error, so you get code like this:

int close(int fd);

if (close(fd)) { /* Something bad happened... */ }

See close manual which returns 0 on success and -1 on failure. For new user, this code is disconcerting, you expect close to return something that is true if it succeed, not the opposite.

2. If you need to store large amount of boolean values, you may want to optimize the storage by using only one bit to represent the value (against 32 bits if you store it in a int), and in C++, std::vector<bool>² is already specialized to do that, so:

std::vector<bool> bvec(8000); // Size ~ 1000 bytes (optimization of std::vector<bool>)
std::vector<int> ivec(8000);  // Size ~ 32000 bytes (32-bits int)

_{¹ There are no advantages if you use them in the same way (e.g. by doing bool b = f(); vs. int b = f(); or the vector<bool> above (if you can replace int by bool without problem in your code, then do so)), but if you use an int to store multiple boolean values using bitwise operations, this is another question.}

_{² Note that this only applies to std::vector<bool>, other containers such as std::array<bool, N> are not optimized because they cannot use proxy object to "represent" a bit value.}

Answer 2

It's mainly a style issue and so it's hard to prove one way is correct. C allows the syntax if(x) where the condition is executed if x is non-zero. So "true" can be a bit of a trap, if(x == true) doesn't always mean what you think. On the other hand, return true is a lot clearer than return 1 in a function like is_valid(). bool can be more memory efficient but that can be an illusion, often it's padded to four bytes anyway for efficiency reasons.

The main issue with bool, though again it is style issue, is that

mywdgt = openwidget("canvaswidget", 256, 256, true);

obviously means open or create a widget, which is a canvas, and is 256 x 256 pixels. But what is the last parameter?

mywdgt = openwidget("canvaswidget", 256, 256, ALLOW_ALPHA);

is a lot clearer. You know what the parameter is and what it does, at a glance. So bool arguments should be avoided in function signatures, use a define instead and say what the flag means.

Answer 3

bool - the built-in Boolean type. A bool can have the values true and false.

So, if you have a scenario in which a boolean type makes sense, e.g., a flag or return value to denote yes/no or success/failure, you would consider using bool.

But then if you have multiple such values, the use of an int(s) would be more appropriate. bool would not be appropriate because the values involved should be restricted to true/false.

Answer 4

To save memory it is highly recommended to use BOOL e.g if we are just checking condition(true or false) or some thing like that.

Bool occupies only 1 byte(generally- smallest addressable size) of memory whereas integer may take 2 or 4 bytes or more depends on compiler.

So its very much advisable to use bool instead integer to store only 1 or 0. Why to waste memory if you can do it in less memory.

And the bool can guarantee to have values only 0 or 1. So it will be appropriate for conditional statements.