C structure

[sajithamol]

What's the difference between these two declarations? struct x1 { ... }; typedef struct { ... } x2;

[scruggsy]

What's the difference between these two declarations? struct x1 { ... }; typedef struct { ... } x2;

For practical purposes, nothing really. They both give a name to the struct.

typedef creates an alias for another type. For instance you can do:

typedef int number;
number myNum = 10; // same as saying "int myNum = 10;"

number is now an alias for type int.
typedef struct {} x2; creates an alias for a type as well. Instead of being an alias for an int, it's an alias for the struct you just defined.

I think C differs from C++ in that you have to use the struct keyword when declaring variables of a struct type:

struct x1 { };
struct x1 myX1Struct;

The typedef gets around that.