Why doesn't the Switch without break statements print all the cases?

Question

The code I encountered is:
int age=42;
switch (age){
case 16:
cout << "Too young"<< endl;
case 42:
cout << "Adult"<< endl;
case 70:
cout << "Senior"<< endl;
default:
cout << "This is the default case"<< endl;
}
And the output is:
Adult
Senior
This is the default case

Answer 1

spandan is correct, switch would go through the cases until it finds the right case and then runs all the cases from then on. that is why it has not run the ones prior to case 42

Answer 2

Yeah, what Zen said!

Remember that C++ (and C) are super old, and so every possible way to squeeze out some performance from machines from the 80s was welcomed. If programming was invented today, there would probably be no switch-statements, but it can be useful, exactly for this so-called "fall-through".

And just for fun, the craziest thing I've ever seen regarding switch statements is "Duff's device", where Tom Duff mushed a while-loop and a switch into one single thing (https://en.wikipedia.org/wiki/Duff%27s_device). I mean, look at that! So gross yet so beautiful.

switch (count % 8) {
case 0: do { *to = *from++;
case 7: *to = *from++;
case 6: *to = *from++;
case 5: *to = *from++;
case 4: *to = *from++;
case 3: *to = *from++;
case 2: *to = *from++;
case 1: *to = *from++;
} while (--n > 0);
}

Answer 3

the switch statement directs to the case that is similar to the given condition. however accoring to the block system the code starts to be running hence after line by line. so actually the switch statement skips the codes before the desired case.
now break actually helps to exit from the loop. you can use break in for or while loops too. so after the codes in the case is exicuted break helps to get out of the switch statement. if you don't use it then simply the next code, that is the next case will be executed.

Answer 4

the switch will encounter the given no. and then starts printing no.s below that no. until it encounters break statement

Answer 5

My guess is that it was implemented like this to allow for the matching of several different values at the same time, like this:
switch(val){
case 1:
case 2:
case 3:
//do something if val is 1, 2, or 3
break;
case 4:
case 5:
//do something else if val is 4 or 5
break;
}

Answer 6

switch statement without break, is just like do while statement, it will execute from the true case until it reach to the break statement, also do while statement executes the codes until it reaches the condition these statements are not similar but some how they have related concepts

Answer 7

None of the cases would have executed if the switch condition was never met by all of cases

In order for any condition when all have no break statement to be executed they should follow one case whitch matches the switch condition

/* please forgive my English */

Answer 8

hehehe so kindly use break statement.

Answer 9

u know what..
just chill

Answer 10

Without the break statement the current case statement excuses infinitely so the other case statements are not executed. So the break statement stops execution of the current case thus making it possible to execute the next case