Random access display
74HC00, 74HC191, 74HC4511
Here's a random access display. It indicates the numbers 0-9 rapidly in order, and stops at one of the numbers when S1 is pressed. You can use it as for roulette or dice.
When you finish wiring, turn power ON. The numbers on the LED display changes rapidly and looks like "8."
Now press S1 and see what happens. The display stops at one of the numbers 0-9.
Now release S1 and the number begins changing rapidly again.
Press and release S1 a few times, and you'll notice that the number on the LED display changes each time you release S1. As you can see by the schematic, the astable multivibrator sends out clock pulses to the counter IC. It stops generating the clock pulses when S1 is pressed.
The counter IC is a decade-down counter, and its output is decoded by the decoder IC and displayed on the LED display.