printf("what do you want to do?(A for conversion from decimal base to binary base ,B for conversion from binary base to decimal base ,C for Operation in binary base, Q for stop):");
scanf(" %c",&auswahl1);
switch(auswahl1){
case'A':
case'a':
printf("Enter a decimal number: ");
scanf("%lld",&dec);
bin1=DecToBin(dec);
printf("%lld in decimal = %lld in binary\n",dec,bin1);
break;
case'B':
case'b':
printf("Enter a binary number: ");
scanf("%lld",&bin1);
dec=BinToDec(bin1);
printf("%lld in binary = %lld in decimalprintf\n");
break;
case'C':
case'c':
break;
case'Q':
case'q':
printf("The programme is terminated.\n");
break;
default:
printf("Invalid selection. Please enter again.\n");