programming-for-dummies

172
Using Comparison Operators
Using Comparison Operators
Unlike math and string operators that can change data, comparison operators
compare two chunks of data to determine which one is bigger than the
other. Table 3-7 lists common comparison operators. When comparison
operators compare two items, the comparison operator returns one of two
values: True or False.
A single comparison operation is also called a conditional expression.
The values True and False are known as Boolean values or Boolean arithmetic.
(The mathematician who invented Boolean arithmetic is named
George Boole.) Computers are essentially built on Boolean arithmetic
because you program them by flipping switches either on (True) or off
(False). All programming ultimately boils down to a series of on-off commands,
which is why machine language consists of nothing but 0’s and 1’s.
Table 3-7
Common Comparison Operators
Comparison Operator What It Means Example Result
= or == Equal 45 = 37 False
A = A
True
< Less than 563 < 904 True
a”< A
False
Greater than 51 > 4 True
A > a
False
>= Greater than or 76 >= 76 True
equal to a > – z False
< > or != Not equal to 46 < > 9 True
a < > a
False
Many curly bracket languages, such as C, use != as their not equal comparison
operator instead of < >.
Curly bracket languages, such as C and C++, use the double equal sign (==)
as the equal comparison operator whereas other languages just use the
single equal sign (=). If you use a single equal sign in C/C++, you’ll assign a
value rather than compare two values. In other words, your C/C++ program
will work, but it won’t work correctly.
Knowing whether two values are equal, greater than, less than, or not equal
to one another is useful to make your program make decisions, which you
read about in Chapter 4 of this mini-book.