What s an int in C#

Creator Code 39 Full ASCII in C# What s an int

The final statement in the program assigns the value stored in m, which is 2, to the variable n The variable n continues to contain the value 2 until it is assigned a new value (The variable n doesn t lose its value when you assign its value to m It s like cloning n)

You can initialize a variable as part of the declaration, like this:

// Declare another int variable and give it the initial value of 1 int p = 1;

This is equivalent to sticking a 1 into that int storage locker when you first rent it, rather than opening the locker and stuffing in the value later Initialize a variable when you declare it In most (but not all) cases, C# initializes the variable for you but don t rely on it to do that You may declare variables anywhere (well, almost anywhere) within a program However, you may not use a variable until you declare it and set it to some value Thus the last two assignments shown here are not legal:

// The following is illegal because m is not assigned // a value before it is used int m; n = m; // The following is illegal because p has not been // declared before it is used p = 2; int p;

Finally, you cannot declare the same variable twice in the same scope (a function, for example)

Most simple numeric variables are of type int However, C# provides a number of twists to the int variable type for special occasions All integer variable types are limited to whole numbers The int type suffers from other limitations as well For example, an int variable can store values only in the range from roughly 2 billion to 2 billion A distance of 2 billion inches is greater than the circumference of the Earth In case 2 billion isn t quite large enough for you, C# provides an integer type called long (short for long int) that can represent numbers almost as large as you can imagine The only problem with a long is that it takes a larger train locker: A long consumes 8 bytes (64 bits) twice as much as a garden-variety 4-byte (32-bit) int C# provides several other integer variable types, as shown in Table 2-1

Table 2-1

Range of Values 128 to 127 0 to 255 32,768 to 32,767 0 to 65,535 2 billion to 2 billion 0 to 4 billion (exact values listed in the Cheat Sheet on this book s Web site) 1020 to 1020 a whole lot 0 to 2 1020 In Use sbyte sb = 12; byte b = 12; short sh = 12345; ushort ush = 62345; int n = 1234567890; uint un = 3234567890U long l = 123456789012L long ul = 123456789012UL

As I explain in the section Declaring Numeric Constants, later in this chapter, fixed values such as 1 also have a type By default, a simple constant such as 1 is assumed to be an int Constants other than an int must be marked with their variable type For example, 123U is an unsigned integer, uint Most integer variables are called signed, which means they can represent negative values Unsigned integers can represent only positive values, but you get twice the range in return As you can see from Table 2-1, the names of most unsigned integer types start with a u, while the signed types generally don t have a prefix You don t need any unsigned integer versions in this book

Integers are useful for most calculations One of this book s authors made it into the sixth grade before he ever found out that anything else existed, and he still hasn t forgiven his sixth-grade teacher for starting him down the slippery slope of fractions Many calculations involve fractions, which simple integers can t accurately represent The common equation for converting from Fahrenheit to Celsius temperatures demonstrates the problem, like this: