Thank you!! but i already resolved the problem..
now may problem is the looping at the last part because when i use
switch statement the new value does not appear but when i use
if statement the new values print

Switch Statement Program
Code:
#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>

#define ARRAY_SIZE 4

int main(){
    //Declare variable
    int x=1,rep,i,temp=0;
    char error[128];
    // Declare array
    int arr[]={2,3,4,5};
    //Declare pointer
    int *ptr;
    
    do{
   system("cls");
   //Show value of variable
    printf("Value of x: %d\n",x);
    //Print address of variable
    ptr=&x;
    printf("Address of x: %p\n\n",ptr);
  
    //Show value of array elements
    printf("The value of elements inside the array:\n\n");
    printf("Position\tElements\tAddresses\n\n");
    for(i=0;i<ARRAY_SIZE;i++){
            ptr=&arr[i];
            printf("%d:\t\t%d\t\t%p\n",i,*ptr,ptr);
    }
    
    //Input address and new value
    printf("\n");
    printf("Please input an address: ");
    scanf("%x",&ptr);
    printf("address\n: %X",ptr);
    printf("Please input the new value: ");
    scanf("%d",&temp);
    *ptr=temp;
    printf("address: %d\n",temp);
    
    printf("Please press the spacebar to continue!!");
    getche();
    while(rep>2||rep<1){
       system("cls");
       printf("Do you want to repeat the computation?\n\n");
       printf("1 - Yes\n");
       printf("2 - No\n");
       scanf("%s",&error);
       rep=atoi(error);
       switch(rep){
                   case 1:
                        main();
                        break;
                   case 2:
                        return 0;
                        break;
                   default:
                           system("cls");
                           printf("Invalid input. Please try again!!!\n");
                           printf("Please press the spacebar to continue!!");
                           getche();
                           break;   
                   }
       }
       }while(rep==1);
    }

If Statement Program

Code:
#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>

#define ARRAY_SIZE 4

int main(){
    //Declare variable
    int x=1,rep,i,q,temp=0;
    char error[128];
    // Declare array
    int arr[]={2,3,4,5};
    //Declare pointer
    int *ptr;
    
    do{
   system("cls");
   //Show value of variable
    printf("Value of x: %d\n",x);
    //Print address of variable
    ptr=&x;
    printf("Address of x: %p\n\n",ptr);
   
    //Show value of array elements
    printf("The value of elements inside the array:\n\n");
    printf("Position\tElements\tAddresses\n\n");
    for(i=0;i<ARRAY_SIZE;i++){
            ptr=&arr[i];
            printf("%d:\t\t%d\t\t%p\n",i,*ptr,ptr);
    }
    
    //Input address and new value
    printf("\n");
    printf("Please input an address: ");
    scanf("%x",&ptr);
    printf("address: %X\n",ptr);
    printf("Please input the new value: ");
    scanf("%d",&temp);
    *ptr=temp;
    printf("address: %d\n",temp);
    
    printf("Please press the spacebar to continue!!");
    getche();
        while(q!=1){
        if(q==2){system("cls");
        printf("Input must be either 1 or 2\n");}
        printf("\n\nReturn to view new list or quit?\n");
        printf("\n[1] Return\n[2] Quit\n");
        scanf("%d",&rep);
        if(rep==1)q=1;
        if(rep==2)return 0;
        if(rep!=1&&rep!=2)q=2;
        }//while q!=1
        q=0;
       }while(rep==1);
    }