Does any body knows,how should i display some digit on seven segment? for example by pressing a push bottom which is connected to "p1.18" port of "lpc2124", digit "1" appears on the seven segment,or by pressing a push bottom connected to "p1.16",digit "2" appers on seven segment.
Separate the problem into sub-problems.
1) Decide what stimuli to use to select digit. Maybe 10 processor pins - one for each digit. But then you have to decide what to do if multiple pins are activated. Or maybe four processor pins detecting a binary combination. But then you need to decide what you should do if combination 10..15 are selected. Or maybe connect a potentiometer to an ADC and measure the turn angle.
2) Figure out what type of display you want to use. Common-anode or common-cathode determines how you drive them. Should you short a pin to ground to light one segment? More processors are good at sinking current than sourcing current. Next thing - can the processor handle all 7 segments concurrently without overload? Using a digit module or using 7 or more discrete LED?
3) Test the software modules individually.
4) Modify the code by having the input from the input select the action for the driver module.