That is not a question about C or C++ but rather about your particular console. Any answer is specific to your target, and possibly in Linux dependent the specific particular terminal emulator.
In most cases a terminal, terminal emulation, or in case of Windows a console window, there will be no support for bold as such - you can often control the colour and brightness of a fixed font however. You can do this in a number of ways - again platform specific - for example through a library such as curses, by sending terminal specific escape sequences, or in Windows through the Win32 Console API.
Without knowing the specific platform, it is not possible to give a specific answer, and even then that answer may not be portable to other platforms.