<< and >> in C++ [duplicate]

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<< and >> in开发者_如何转开发 C++

I don't quite understand what this means...I'm just learning C++ from my very very very basic Python experience...and so this may be a very stupid question. My question is...say you have your classic "Hello World" program and you have the line:

cout<<"Hello World!"<<endl;

what does the << mean...because I was just looking at using input in C and saw that you'd do something like:

int i;
cin>>i;

and I noticed that it has >> instead of << and I've read that those are bitwise shifts...and I don't exactly understand what those are...but I think it might be different here...Help...Thanks in advance

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Look up C++ operator overloading. C++ allows you to overload certain operators (such as arithmetic operators like +, - or *) to provide certain functionality to user-defined classes, such as:

Foo x = 100;
Foo y = 200;
x = x + y;

The built-in C++ IOstreams library is meant to replace the C stdio.h library functions like printf. It overloads the << and >> operators to mean "insert into a stream" and "extract from a stream" respectively. So, saying:

std::cout << "Hello world";

...will insert the string "Hello World" into the standard output stream cout, which is generally associated with console output. IO Streams can be used to print something to the screen, write data to a file, insert data into a string buffer, and can be extended for many other purposes (sockets, pipes, etc.)

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They're indeed bitwise shifts. Numbers in computers are represented in binary form.

Example: 10 = 1010 (8x1 + 4x0 + 2x1 + 1x0).

Now, a shift just moves all numbers to the right or left.

Left shift:
10100 and that's (16x1 + 8x0 + 4x1 + 2x0 + 1x0) or 20. You multiplied by two!

Right shift:
101 (4x1 + 2x0 + 1x0) or 5. You divided by two!

It's really just another way to divide or multiply by 2.

Now, they're all so used to pump data in a graphical way.

The data goes from your input, cin to i:

int i;
cin>>i;

And the data goes from "Hello world" to the output, cout:

cout<<"Hello World!"<<endl;