12.3 typedef

C++ allows you to define your own variable types through the typedef statement. This provides a way for you to extend C++'s basic types. The general form of the typedef statement is:

typedef type-declaration; 

The type-declaration is the same as a variable declaration except a type name is used instead of a variable name. For example:

typedef int width; // Define a type that is the width of an object

defines a new type, width, that is the same as an integer. So the declaration:

width box_width; 

is the same as:

int box_width; 

At first glance, this is not much different from:

#define width int 

width box_width; 

However, typedefs can be used to define more complex objects that are beyond the scope of a simple #define statement, such as:

typedef int group[10]; 

This statement defines a new type, group, which denotes an array of 10 integers. For example:

int main(  ) 
{ 
    typedef int group[10];     // Create a new type "group"

    group totals;              // Use the new type for a variable

    // Initialize each element of total
    for (i = 0; i < 10; ++i) 
        totals[i] = 0;