File content as of revision 3:50c27e4261e2:

#include "mbed.h"

//DigitalOut led1(LED1);
DigitalOut led1(P0_13); //nRF52840 PDK io
DigitalOut led2(P0_14);
DigitalOut led3(P0_15);
DigitalOut led4(P0_16);


InterruptIn button1(P0_11);//(USER_BUTTON nRF52840 PDK);
InterruptIn button2(P0_12);
InterruptIn button3(P0_24);
InterruptIn button4(P0_25);

void button1_pressed()
{
  led1 = led2 =led3 =led4 = 1;
  led1 = 0;
  
}

void button1_released()
{
  led1 = led2 =led3 =led4 = 1;
  //led1 = 0;
}

void button2_pressed()
{
  led1 = led2 =led3 =led4 = 1;
  led2 = 0;
  
}

void button2_released()
{
  led1 = led2 =led3 =led4 = 1;
  //led1 = 0;
}

void button3_pressed()
{
  led1 = led2 =led3 =led4 = 1;
  led3 = 0;
 // wait(0.1);
}

void button3_released()
{
  led1 = led2 =led3 =led4 = 1;
  //led1 = 0;
}

void button4_pressed()
{
  led1 = led2 =led3 =led4 = 1;
  led4 = 0;
  
}

void button4_released()
{
  led1 = led2 =led3 =led4 = 1;
  //led1 = 0;
}


// main() runs in its own thread in the OS
// (note the calls to Thread::wait below for delays)

int main() {
    led1 = led2 =led3 =led4 = 0;
    
    button1.fall(&button1_pressed);
    button1.rise(&button1_released);
    
    button2.fall(&button2_pressed);
    button2.rise(&button2_released);

    button3.fall(&button3_pressed);
    button3.rise(&button3_released);

    button4.fall(&button4_pressed);
    button4.rise(&button4_released);

    
    while (true) {
   //     led1 = !led1;
   //     wait(0.5);
   //     led2 = !led2;
   //     wait(0.5);
   //     led3 = !led3;
   //     wait(0.5);
   //     led4 = !led4;
   //     wait(0.5);
    }
}