i have 100 slots numbered from 0-99 and i have to indicate which slot is nearest to the starting point i.e 0.could anyone help me how to indicate which is nearest slot that is empty.consider a logic '0' from a filled slot and a logic '1' from an empty slot. i need to use digital electronics (TTL LOGIC)to develop the logic and display the decimal number of the NEAREST EMPTY slot on a seven segment display.for eg if slot 13 and 15 are empty, seven segment has to display 13.

 

I see the priority encoder idea got abandoned.

You could make a clocked counter that rolls over at 99. Detecting any slot latches the count into the display and resets the count to 0. Might be a lot clunkier than the priority encoders because of the decoding logic needed to check each slot.