Seven Segment displays are used in a number of systems to display the numeric information. The seven segment can display one digit at a time. Thus the no. of segments used depends on the no. of digits in the number to be displayed. Interfacing seven segment with a controller or MCU is tricky. This article explains the interfacing of seven segment with MCU AT89C51. It displays the digits 0 to 9 continuously at a predefined time delay.