Every variable has a data type. typedef is used to define new data type names to make a program more readable to the programmer.
For example:
|
main() | main()
{ | {
int money; | typedef int Pounds;
money = 2; | Pounds money = 2
} | }
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These examples are EXACTLY the same to the compiler. But the right hand example tells the programmer the type of money he is dealing with.
A common use for typedef is to define a boolean data type as below.
Note: Recent C++ compilers have introduced a boolean datatype.
typedef enum {FALSE=0, TRUE} Boolean
main ()
{
Boolean flag = TRUE;
}
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And as a final example, how about creating a string datatype?
typedef char *String;
main()
{
String Text = "Thunderbird";
printf("%s\n", Text);
}
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The main use for typedef seems to be defining structures. For example:
typedef struct {int age; char *name} person;
person people;
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Take care to note that person is now a type specifier and NOT a variable name.
As a final note, you can create several data types in one hit.
typedef int Pounds, Shillings, Pennies, Dollars, Cents; |
Here is a rather heavy example of typedef.
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