You create or define a variable by stating its type, followed by one or more spaces, followed by the variable name and a semicolon. The va...
You create or define a variable by stating its type, followed by one or more spaces, followed by the variable name and a semicolon. The variable name can be virtually any combination of letters, but cannot contain spaces. Legal variable names include x, J23qrsnf, and myAge. Good variable names tell you what the variables are for; using good names makes it easier to understand the flow of your program. The following statement defines an integer variable called myAge:
int myAge;
As a general programming practice, avoid such horrific names as J23qrsnf, and restrict single-letter variable names (such as x or i) to variables that are used only very briefly. Try to use expressive names such as myAge or howMany. Such names are easier to understand three weeks later when you are scratching your head trying to figure out what you meant when you wrote that line of code.
Try this experiment: Guess what these pieces of programs do, based on the first few lines of code:
Example 1
main()
{
unsigned short x;
unsigned short y;
ULONG z;
z = x * y;
}
Example 2
main ()
{
unsigned short Width;
unsigned short Length;
unsigned short Area;
Area = Width * Length;
}
Clearly, the second program is easier to understand, and the inconvenience of having to type the longer variable names is more than made up for by how much easier it is to maintain the second program.
Case Sensitivity
C++ is case-sensitive. In other words, uppercase and lowercase letters are considered to be different. A variable named age is different from Age, which is different from AGE.
NOTE: Some compilers allow you to turn case sensitivity off. Don't be tempted to do this; your programs won't work with other compilers, and other C++ programmers will be very confused by your code.
There are various conventions for how to name variables, and although it doesn't much matter which method you adopt, it is important to be consistent throughout your program.
Many programmers prefer to use all lowercase letters for their variable names. If the name requires two words (for example, my car), there are two popular conventions: my_car or myCar. The latter form is called camel-notation, because the capitalization looks something like a camel's hump.
Some people find the underscore character (my_car) to be easier to read, while others prefer to avoid the underscore, because it is more difficult to type. This book uses camel-notation, in which the second and all subsequent words are capitalized: myCar, theQuickBrownFox, and so forth.
NOTE: Many advanced programmers employ a notation style that is often referred to as Hungarian notation. The idea behind Hungarian notation is to prefix every variable with a set of characters that describes its type. Integer variables might begin with a lowercase letter i, longs might begin with a lowercase l. Other notations indicate constants, globals, pointers, and so forth. Most of this is much more important in C programming, because C++ supports the creation of user-defined types and because C++ is strongly typed.
