Main menu: 
A. Add new number. 
D. Delete a number. 
P. Print all numbers. 
==>A 
Add number: 30  
Main menu: 
A. Add new number. 
D. Delete a number. 
P. Print all numbers. 
==>A 
Add number: 50  
Main menu: A. 
Add new number. 
D. Delete a number. 
P. Print all numbers. 
==>P 
List of all numbers: 30,50,  
Main menu: 
A. Add new number. 
D. Delete a number. 
P. Print all numbers. 
==>D 
Enter number to delete: 34 
Error: No such number...

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
int i=0;
void Check (char chr, int *ptr);
char Main_menu (char chr, int *ptr)
{
	do {
	printf("\n Main menu: \n A. Add new number. \n D. Delete a number. \n P. Print all numbers. \n E. Exit \n ==> ");
	scanf("%c", &chr);
	if (chr=='e' || chr=='E')
		exit(0);
	}
	while (chr!='A' && chr!='a' && chr!='d' && chr!='D' && chr!='P' && chr!='p');
	Check (chr, ptr);
	return chr;
}
void Check (char chr, int *ptr)
{
	int a, num;
	if (chr=='A' || chr=='a')
	{
		i++;
		printf("Add number: ");
		scanf("%d", &num);
		ptr = (int*)realloc(ptr, sizeof(int) * i);
		ptr=num;
	}
	else if (chr=='D' || chr=='d')
	{
		printf("Enter number to delete: ");
		scanf("%d", &num);
		for (a=0 ; a<i ; a++)
		{
			if (ptr==num)
			{
				i--;
				for ( ; a<i ; a++)
					ptr==ptr;
				ptr = (int*)realloc(ptr, sizeof(int) * i);
				return;
			}
			if (a==i-1)
			{
				printf("Error: No such number...");
				Main_menu;
			}
		}
	}
	else if (chr=='P' || chr=='p')
	{
		for (a=0 ; a<i ; a++)
			printf("%d, ", ptr);
	}
}
int main()
{
	int *ptr;
	char chr;
	do {
	chr = Main_menu(chr, ptr);
	}
	while (chr!='E' || chr!='e');
	getchar();
}

$ guy
 Main menu:
 A. Add new number.
 D. Delete a number.
 P. Print all numbers.
 E. Exit
 ==> a
Add number: 5
Segmentation fault
$

 $ guy
 Main menu:
 A. Add new number.
 D. Delete a number.
 P. Print all numbers.
 E. Exit
 ==> d
Enter number to delete: 5
 Main menu:
 A. Add new number.
 D. Delete a number.
 P. Print all numbers.
 E. Exit
 ==>
 Main menu:
 A. Add new number.
 D. Delete a number.
 P. Print all numbers.
 E. Exit
 ==>