4 x 4 matrix keypad converter

We discussed the converter in class today, we i didn't understand. I'm having difficulties understanding how it works mainly, column scanning inputs and row connection outputs. Can someone please explain the functionality by using examples?

Thank you

The keys in the matrix keyboard are arranged in a matrix arrangement in order to utilize the port pins of the microcontrollers efficiently. Here we can interface 16 keys by using just 8 pins of microcontroller. This is shown in the circuit diagram.

As shown in the circuit diagram, the rows are connected to 4 pins of a port, the columns are connected to other four pins, we configure rows as input and columns as output. By grounding one column and setting high all other columns, now by observing the status of the rows, we can come to know which button is pressed. For example, if we ground the first column and if the first row is low, then the first button is pressed. We know that microcontrollers are really fast, therefore they can detect the key press in microseconds, if we hold the switch for long time (for a microcontroller long time is in milliseconds), the microcontroller is triggered more than once, also there is a problem of switch debounce because of the spring action of the switch. To eliminate these problems we should introduce some amount of delay after every key press.