File content as of revision 2:6a2101a16cef:

#include "mbed.h"
// #define BUTTON1 A1
#define BUTTON1 p14
BusOut myLeds(LED1,LED2,LED3,LED4);
DigitalIn button(BUTTON1);

void nibbleLeds(int value);
void printb(uint8_t x);
int modifyBit(int x, uint8_t position, bool State);
const int INIT = 0x03;


int main() {
    int anzahl, anz;
    uint8_t value = INIT;
    // anzahl = lauflicht(true, 400, anz = 0);
    
    printf("anzahl = %d\n", anzahl);
    nibbleLeds(value);
    printb(myleds);
    value = modifyBit(value, 2, 1);
    printb(myleds);
    printb(modifyBit(value, 3, 1));
    wait(0.1);
}

void nibbleLeds(int value) {
    myLeds = value % 16;
}

void printb(uint8_t x){
    for(int i = sizeof() << 3; i; i--)
        putchar('0' + ((x >> (i - 1)) & 1));
    printf("\n");
}

int modifyBit(int x, uint8_t position, bool State){
    int mask = 1 << position;
    int state = int(State);
    return (x & ~mask) | ((state << position) & mask);
}