iec2011007 - 6 months ago 28

C Question

Is there a way for the user to input a binary number in C or C++?

If we write something like

`int a = 0b1010;`

std::cout << a << std::endl

Then the output comes out to be 10 (when using the appropriate compiler extensions).

but when we try to write

`int n;`

std::cin >> n;

int t = 0bn;

It gives us an error so can anyone suggest that how can we directly read binary number as input rather than using string to store input?

Answer

There is a bit of confusion here, let's disentangle it a bit.

`0b1010`

is an*integer literal*, a constant, compile-time integer value written in base 2. Likewise,`0xA`

is a literal in base 16 and`10`

is in base 10.**All of these refer to the same integer**, it is just a different way of telling the compiler which number you mean. At runtime, in memory, this integer is*always*represented as a base-2 number.`std::cout << a`

; takes the integer value of`a`

and outputs a string representation of it. By default it outputs it in base 10, but you can i.e use the`std::hex`

modifier to have it output it in base 16.**There is no predefined modifier to print in binary**. So you need to do that on your own (or google it, it is a common question).`0b`

at last, is*only*used to define integer literals. It is**not**a runtime operator. Recall, all`int`

s are represented as base 2 numbers in memory. Other bases do not exist from a machine point of view,`int`

is`int`

, so there is nothing to convert. If you need to read a binary number from a string, you would roll the reverse code to what you do to print it (`std::cin >> n`

assumes that the input is a base 10 number, so it reads a wrong number if the input is actually intended to be in base 2).