How to delay output to a stream in c++?

Question

C++ / C#

Help me please.
I wrote like this:
cout <<"Loading ...00%";
sleep(3);
cout<<"\b\b\b99%";
And he does not want to break the stream, so he does not display the first message, makes a delay, and then displays a message with 99 instead of 00

Answer 1

cout - buffered output.
Flush cout.flush
() buffer

Answer 2

sleep(3); // specify time in milliseconds