InsertionSort@pointers,functions

#include<stdio.h>

void swap(int* a, int* b);

int main(){
    int first=0,last=0,j=0,n=0,mark=0,bool=0,arr[15];

        do{
            // entering array

            printf("enter the size of the array(less than 15): ");
            scanf("%d",&n);
            printf("enter the array members: ");
            for(j=0;j<n;j++){
                scanf("%d",&arr[j]);
            }
            printf("\nthe entered array: ");
                for(j=0;j<n;j++){
                    printf("%d ",arr[j]);
            }


            // sorting array

            last=(n-1);

            for(j=0,mark=0;mark<last;mark++){
                j=mark+1;
                while(arr[j-1]>arr[j]){
                    swap(&arr[j-1],&arr[j]);
                    if(j>1) // this step is CRUCIAL, as when j=1, decrementing it will result in arr[-1] to be compared in next while iteration
                    j--;
                }
            }

            // printing the sorted array

            printf("\nthe sorted array: ");
                for(j=0;j<n;j++){
                    printf("%d ",arr[j]);
            }

            printf("\n\niterate again for new number?\n yes(1) or no(0)\n enter choice: ");
            scanf("%d",&bool);

        }while(bool==1);

    return 0;
}

void swap(int* a, int* b){
    *a=*a + *b;
    *b=*a-*b;
    *a=*a-*b;
}