help me understanding typedef

[gurpartap]

How typedef used in below code working:
Because generally we use typedef as:
Typedef type_name new_type_name;
example: typedef unsigned int u_int32;
But in example below there is no name to function pointer.

/* insertion_sort.h */
 
typedef int (*callback)(int, int);
void insertion_sort(int *array, int n, callback comparison);
	
/* insertion_main.c */
 
#include<stdio.h>
#include<stdlib.h>
#include"insertion_sort.h"
 
int ascending(int a, int b)
{
    return a > b;
}
 
int descending(int a, int b)
{
    return a < b;
}
 
int even_first(int a, int b)
{
    /* code goes here */
}
 
int odd_first(int a, int b)
{
    /* code goes here */
}
 
int main(void)
{
    int i;
    int choice;
    int array[10] = {22,66,55,11,99,33,44,77,88,0};
    printf("ascending 1: descending 2: even_first 3: odd_first 4: quit 5\n");
    printf("enter your choice = ");
    scanf("%d",&choice);
    switch(choice)
    {
        case 1:
            insertion_sort(array,10, ascending);
            break;
        case 2:
            insertion_sort(array,10, descending);
         case 3:
            insertion_sort(array,10, even_first);
            break;
        case 4:
            insertion_sort(array,10, odd_first);
            break;
        case 5:
            exit(0);
        default:
            printf("no such option\n");
    }
 
    printf("after insertion_sort\n");
    for(i=0;i<10;i++)
        printf("%d\t", array[i]);
    printf("\n");
     return 0;
}
	
/* insertion_sort.c */
 
#include"insertion_sort.h"
 
void insertion_sort(int *array, int n, callback comparison)
{
    int i, j, key;
    for(j=1; j<=n-1;j++)
    {
        key=array[j];
        i=j-1;
        while(i >=0 && comparison(array[i], key))
        {
            array[i+1]=array[i];
            i=i-1;
        }
        array[i+1]=key;
    }

[coder777]

But in example below there is no name to function pointer.

There is. The name is callback.

In C++11 you can use using instead. The syntax is easier to read:

using callback = int (*)(int, int);
void insertion_sort(int *array, int n, callback comparison);