stdout stands for standard output stream and it is a stream which is available to your program by the operating system itself. It is already available to your program from the beginning together with stdin and stderr.
What they point to (or from) can be anything, actually the stream just provides your program an object that can be used as an interface to send or retrieve data. By default it is usually the terminal but it can be redirected wherever you want: a file, to a pipe goint to another process and so on.
@K Scott Piel wrote a great answer here, but I want to add one important point.
Note that the stdout stream is usually line-buffered, so to ensure the output is actually printed and not just left sitting in the buffer waiting to be written you must flush the buffer by either ending your printf statement with a \n
Ex:
printf("hello world\n");
or
printf("hello world");
printf("\n");
or similar, OR you must call fflush(stdout); after your printf call.
Ex:
printf("hello world");
fflush(stdout);
Read more here: Why does printf not flush after the call unless a newline is in the format string?
stdout is the standard output stream in UNIX. See http://www.gnu.org/software/libc/manual/html_node/Standard-Streams.html#Standard-Streams.
When running in a terminal, you will see data written to stdout in the terminal and you can redirect it as you choose.
It depends.
When you commit to sending output to stdout, you're basically leaving it up to the user to decide where that output should go.
If you use printf(...) (or the equivalent fprintf(stdout, ...)), you're sending the output to stdout, but where that actually ends up can depend on how I invoke your program.
If I launch your program from my console like this, I'll see output on my console:
$ prog
Hello, World! # <-- output is here on my console
However, I might launch the program like this, producing no output on the console:
$ prog > hello.txt
but I would now have a file "hello.txt" with the text "Hello, World!" inside, thanks to the shell's redirection feature.
Who knows – I might even hook up some other device and the output could go there. The point is that when you decide to print to stdout (e.g. by using printf()), then you won't exactly know where it will go until you see how the process is launched or used.
stdout is the standard output file stream. Obviously, it's first and default pointer to output is the screen, however you can point it to a file as desired!
Please read:
http://www.cplusplus.com/reference/cstdio/stdout/
C++ is very similar to C however, object oriented.
Source: Stackoverflow.com