programming-for-dummies

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Declaring Variables
Other programmers prefer to use uppercase letters at the beginning of each
new word, such as
SalesTaxFor2008;
You can always mix and match both conventions if you want, such as
SalesTaxFor_2008;
No matter which naming style you prefer, it’s best to stick with one style to
prevent your program from looking too confusing with so many different
variable naming styles all over the place.
Every variable needs a unique name. If you try to give two variables identical
names, the computer gets confused and refuses to run your program.
In some languages, such as the curly bracket family, which includes C, C++,
and Java, variable names are case-sensitive. Therefore, a variable named
salestax is considered completely different than a SalesTax variable.
Creating variables in a command
The simplest way to create a variable is when you need it in a command.
Suppose you have a program that asks the user for his annual salary, such as
the following command (written in the Python programming language):
salary = input(“What is your annual salary?”)
This command displays, “What is your annual salary?” on-screen
and waits for the user to type in a number.
As soon as the user types in a number, such as 20000, the program needs a
variable to store this number. In this example, the program creates a salary
variable and stores the number 20000 in that variable.
Creating variables whenever you need them in a command is simple and
convenient — and potentially troublesome if you aren’t careful. The biggest
problem is that when you create a variable within a command, that variable
can store any type of data.
Variables can hold two types of data:
✦ Numbers, which are typically used to represent quantities or measurements.
✦ Text (sometimes called strings, as in “text strings”) is used to represent
non-numeric data, such as names or mailing addresses.