Why is a char and a bool the same size in c++?

Question

I\'m reading The C++ Programming Language. In it Stroustrup states that sizeof(char) == 1 and 1 <= sizeof(bool). The specifics depend

Answer 1

A byte is the smallest addressable unit of memory.

Consider the following code:

    bool b[9];
    bool *pb0 = &b[0];
    bool *pb1 = &b[1];

    for (int counter=0; counter<9; ++counter)
    {
         // some code here to fill b with values
         b[counter] = true;

    }

If bool is stored as 1 bit, then pb0 will equal pb1, because both have the same address. This is clearly not desirable!

Additionally the assignment in the loop will result in non-trival assembly code. It will involve a different bit shift in each iteration of the loop. In high-performance software, those extra bit-shift operations can slow down the application needlessly.

The STL library provides a work-around in situations where space DO matter. The use of std::vector<bool> will store bool as 1 bit. The paradox of the example above do not apply because

• the overloading of operator[] hides the rigors of the bit shift operation
• the use of iterators instead of pointers give additional flexibilty to the implementation