Push button

How can I take a plus 1 value for a variable ussing push button ????
at each push of button it must take +1 count
i tried this but didnt got the output

if(digitalRead(BUTTONG) == HIGH){

g_fb = g_fb + 1;

The state change detection example.

Here's the warning.

If you are going to use a pushbutton, you must incorporate "de-bouncing" code (so you need to research that - note de-bouncing in software, not hardware). Because of contact bounce, a single press of the button is detected by the microcontroller as something like 5 to 15 separate contacts over a 5 to 10 millisecond interval so your count may advance by (many) more than one.

And it is very unwise to attempt to use interrupts for responding to pushbuttons.