programming-for-dummies

148
Using Different Data Types
Using Different Data Types
Defining a specific data type makes it easy to
✦ Know the type of data a variable can hold (either numbers or text).
✦ Restrict the range of data the variable can hold.
✦ Identify whether a variable can hold a number or text can keep your
program from trying to add or multiply a number by a word, which
doesn’t work. Figure 2-3 shows the different categories of data types
within most programming languages.
Common Programming Data Types
Data Types
Figure 2-3:
Different
data types
that can
hold a range
of values.
Boolean
(0 or 1)
Integer
(Whole numbers)
Byte
(0–255)
Integer
(-32,768–
32,767)
Long
(-2.147e9–
2.127e9)
Numbers
Real
(Decimal numbers)
Single
(-3.403e38–
2.147e9)
Double
(-1.798e308–
1.798e308
Character
(1 character)
Text
String
(0 to 2 billion characters
Defining the range of data can prevent a variable from storing incorrect data.
For example, if your program asks the user to type in his age, invalid data
would include negative numbers, zero, and extremely large numbers, such
as 259.
The range of numbers listed for Long, Single, and Double data types are
listed as exponential numbers (that’s the little e). So the Long data type can
store a number as large as 2.147 with the decimal place moved nine places to
the right or approximately 2,147,000,000.
Every programming language offers different data types, so use Figure 2-3 as
a guideline rather than a strict reference.
For example, if you want to store a person’s age in a variable, you probably
want to store it as a whole number (such as 45) rather than a real number
(such as 45.029).
Next, you want to choose a data type that contains the range of values a
person’s age might be. From Figure 2-3, you can see that a Boolean data