How to draw a pixel by changing video memory map directly in a C program (without library functions)

Is it possible to display a black dot by changing values in the screen(video ie monitor) memory map in RAM using a c program?

I don't want to use any library functions as my primary aim is to learn how to develop a simple OS. I tried accessing the starting screen memory map ie 0xA0000 (in C).

I tried to run the program but got a Segmentation Fault since no direct access is provided. In super user, the program gets executed without any change.

Currently I am testing in VirtualBox.