It is necessary to understand basic I/O operations of PIC18F4550 before dealing with its complexities. This article presents a way to take simple output from a PIC [[wysiwyg_imageupload::]]microcontroller. This learning would also help in interfacing of external devices with the controller. Here the output from the microcontroller is taken on a set of LEDs which are made to blink in an alternate fashion.  PIC18F4550 has a total of 35 I/O (input-output) pins which are distributed among 5 Ports. As opposed to a basic 8051 microcontroller like AT89C51 which has most of the port pins serving single function, the port pins of a PIC microcontroller are multiplexed to serve more than one purpose. The 35 I/O pins of PIC18F4550 are also multiplexed with one or more alternative functions of controller’s various peripherals. Each Port of a PIC microcontroller corresponds to three 8-bit registers which should be configured to use the Port for general I/O purpose.