Increase pointer value in C language

/*
Example: increment pointer value in C language
*/

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char const *argv[]) {
    int i = 6;
    int*ptr ;
    *ptr = i;

    (*ptr)++; // increment the value of（*ptr）,that is the value of i
    printf("%d\n",*ptr); 
    printf("%d\n",ptr);
    *ptr++; // The value of ptr address is incremented 。 * has priority over ++
    printf("%d\n",ptr);
    printf("%d\n",*ptr); // the value of new address, it's not initialized, so it is 0.

    return 0;

}

example of output:

7
46423984
46423988
0

|--------|--------\
|42000004|7       |
|--------|--------|
|     ....        |
|--------|--------|
|46423984|42000004|
|--------|--------|
|46423988|0       |
|--------|--------|