I have a question.
switch(car1){
case 'a':cout<<"es la letra A o B\n";
case 'b':cout<<"es la letra A o B\n";
}
In this case, is it possible that when the cases are put, when you want car1 to be to or b say the message instead of having to write each case ?
When a case of switch does not include break , all subsequent cases are executed until finding a break , so in your case:
switch(car1){
case 'a':cout<<"es la letra A o B\n";
case 'b':cout<<"es la letra A o B\n";
}
When car1 is 'a' the message "es la letra A o B\n" will be written twice (the case of 'a' and then follow and write the case of 'b' . When car1 is 'b' the message it will be written once.
Therefore:
switch(car1){
case 'a':
case 'A':
case 'b':
case 'B':
cout<<"es la letra A o B\n";
}
It will print the same message, once, when car1 is a , b , A or B . Some compilers emit an alarm with the previous code, to avoid it add the attribute [[fallthrough]] 
switch(car1){
case 'a':
[[fallthrough]];
case 'A':
[[fallthrough]];
case 'b':
[[fallthrough]];
case 'B':
cout<<"es la letra A o B\n";
}
If what you want is that in either case (A or B) print the message you should only place
case 'a':
case 'b':cout<<"es la letra A o B\n";
break;
Because if 'a' is going to continue until you find some break; that breaks the switch , if you put it on both sides (as you have it) it will impimpress 2 times the message if the letter is' a'o 1 time only if it's 'b'