typedef is a language construct that associates a name to a type.
You use it the same way you would use the original type, for instance
typedef int myinteger;
typedef char *mystring;
typedef void (*myfunc)();
using them like
myinteger i; // is equivalent to int i;
mystring s; // is the same as char *s;
myfunc f; // compile equally as void (*f)();
As you can see, you could just replace the typedefed name with its definition given above.
The difficulty lies in the pointer to functions syntax and readability in C and C++, and the typedef can improve the readability of such declarations. However, the syntax is appropriate, since functions - unlike other simpler types - may have a return value and parameters, thus the sometimes lengthy and complex declaration of a pointer to function.
The readability may start to be really tricky with pointers to functions arrays, and some other even more indirect flavors.
To answer your three questions
Why is typedef used? To ease the reading of the code - especially for pointers to functions, or structure names.
The syntax looks odd (in the pointer to function declaration) That syntax is not obvious to read, at least when beginning. Using a
typedefdeclaration instead eases the readingIs a function pointer created to store the memory address of a function? Yes, a function pointer stores the address of a function. This has nothing to do with the
typedefconstruct which only ease the writing/reading of a program ; the compiler just expands the typedef definition before compiling the actual code.
Example:
typedef int (*t_somefunc)(int,int);
int product(int u, int v) {
return u*v;
}
t_somefunc afunc = &product;
...
int x2 = (*afunc)(123, 456); // call product() to calculate 123*456
