sir thank u for the idea u gave last tym.
now i m facing one more problem in proteus. after uploading the program in the microcontroller, when i m running it, the led is glowing on its own. according to my circuit and program, the led should glow only when i m pressing the push buton, but instead the led is glowing even when i m not pushing the button. when i used a NAND gate connecting the output and input ports and the led is connected to the output of that nand gate.
i m not getting the reason why is this happening.
here is the snapshot of what i have tried in proteus for four leds. sir if u could tell me why the circuit is not working the way i want it to. the simple logic that i m using is if input is zero then output should go high.