Can a Win32 console application detect if it has been run from the explorer or not?

See http://support.microsoft.com/kb/99115, "INFO: Preventing the Console Window from Disappearing".

The idea is to use GetConsoleScreenBufferInfo to determine that the cursor has not moved from the initial 0,0 position.

Code sample from @tomlogic, based on the referenced Knowledge Base article:

// call in main() before printing to stdout
// returns TRUE if program is in its own console (cursor at 0,0) or
// FALSE if it was launched from an existing console.
// See http://support.microsoft.com/kb/99115
#include <stdio.h>
#include <windows.h>
int separate_console( void)
{
    CONSOLE_SCREEN_BUFFER_INFO csbi;

    if (!GetConsoleScreenBufferInfo( GetStdHandle( STD_OUTPUT_HANDLE), &csbi))
    {
        printf( "GetConsoleScreenBufferInfo failed: %lu\n", GetLastError());
        return FALSE;
    }

    // if cursor position is (0,0) then we were launched in a separate console
    return ((!csbi.dwCursorPosition.X) && (!csbi.dwCursorPosition.Y));
}

GetConsoleTitle()

I've seen code which performs

if (!GetConsoleTitle(NULL, 0) && GetLastError() == ERROR_SUCCESS) {
    // Console
} else {
    // GUI
}

BUT... I've found that AttachConsole() is more helpful

In C++ (off the top of my head, and I'm no C++ programmer)

if (!AttachConsole(ATTACH_PARENT_PROCESS)) {
    // GUI
} else {
    // Console, and you have a handle to the console that already exists.
}

Is more effective. Additionally, if you find yourself in a GUI environment and would like to stay there as long as you can, but later find something catastrophic has happened that could really use a dump to a console window (you can't be arsed writing an edit box window to lot it to or attach to the NT System log and throw up a MessageBox()) well then you can AllocConsole() later on in the process, when GUI methods have failed.

I believe cmd.exe sets the CMDCMDLINE and CMDEXTVERSION environemntal variables when it starts. So if these are set your program was most probably started from a shell.

This isn't foolproof but it's something.

It's also possible to determine your parent PID in a few convoluted and possibly unreliable ways, or so I gather. You may want to look into that.