if (m=='a')
if ((n<=19)&&(n>=1))
cout<<"Your zodiac sign is Capricorn.";
The braces are optional, but be careful since not using braces can lead to subtle hard to find bugs. For example look at the following:
1 2 3 4
if (m=='a')
z = 34;
if ((n<=19)&&(n>=1))
cout<<"Your zodiac sign is Capricorn.";
In this case only the "z = 34;" is part of that first if statement, because without the braces control statements contain only one line following the statement unless braces are used. Because of this, I recommend novice programmers always use braces with all control statements, even when not technically required.