Consume Keystroke

That will depend what kind of applications are you building: console, Win32, MFC. But a generica aproach is something like this:

c = getch();   // Wait to read first keystroke
// some processing
while (getch()) {}  // Read (comsume) all keystrokes triggered
// some other processing

Sorry, maybe not a good example. Try with this:

// this header is needed to use getch() and kbhit()
#include "conio.h"
 
int main ()
{
    // some code here

int c;
c = getch();   // Wait to read first keystroke
// some processing
while (kbhit())  // verify if key exist in buffer
      { getch(); }  // Read (comsume) all keystrokes triggered
// some other processing

    return 0;
}

>>VC++6 Windows:
My application is windows application MDIBased;
containing many child forms

There are many tecniques, also you can control the PreTranslateMessage event in your application.
You can filter all the WM_CHAR messages is a flag is on

Create a flag member in your CWinApp derived object:
       bool m_IgnoreKeys;

Then create an event with the ClassWizard (Ctrl-W) for your app object, and control WM_CHAR specific message

(inside CYourApp::PreTranslateMessage)
   if (msg==WM_CHAR) {
       if (!m_IgnoreKeys)        // if m_IgnoreKeys = false
            return FALSE;          // Do nothing
   }
// else continue with pretranslatemessage