brekibg a loop

which function can i use in c/c++ so that as soon as i press a certain character then the loop breaks away goes into the next loop.
for example:

Code:

for(..;..;..;)  /*loop1*/
{....;
.....;       /*now if i press any 'a' when loop 1 is excuting  then it should go to loop 2
.....;
}
if(getch()=='a')  /* loop 2*/
for (..;..;..)
...;
...;
..;