Binary storage of characteristics

[XLR8TD]

I'm writing a program that is basically a 20Q game. I need to store characteristics as binary numbers in a text file where each digit represents a different characteristic, but I'm not sure how to go about it. Anyone know how to manipulate certain digits with Boolean expressions then read them digit by digit?

[KRAkatau]

This would probably do the job for you:
http://www.cplusplus.com/reference/bitset/bitset/

File reading-writing using this data structure is pretty much trivial.

If you need to do it by hand - use bitwise operators. Some example:

std::string s = "1101";
int num = 0;
int base = 1;

for (size_t i = 0; i < s.size(); ++i) {
    num |= (s[i] - '0') * base;
    base <<= 1;
}

// Access characteristic number 3
if (num & (1 << 3)) {
   // characteristic number 3 is '1'  
}

// Clear characteristic number 3
num &= ~(1 << 3);

// Set characteristic number 3
num |= 1 << 3;

// etc. 

Some things to think of: do you really need to store these characteristics as bits? How many of them are there? Will these characteristics always be booleans? Maybe you should go for a more flexible way of storing?