stack implementation using array

Data Structures/stack/main.c

@@ -1,40 +1,98 @@
-/*
-    author: Christian Bender
-
-    This is the main-program for testing the stack.
-*/
-
-#include <stdio.h>
-#include <stdlib.h>
-
-#include "stack.h"
+//program for stack using array 
 
+#include<stdio.h>
+void push();
+void pop();
+void peep();
+void update();
 int main()
 {
-
-    int MAX = 55;
-    int field[MAX];
-    int i; /* for the loop */
-    int *pInt = NULL;
-
-    initStack();
-
-    /* pushs some elements onto stack */
-    for (i = 0; i < MAX; i++)
+    int n,a[100],top=0;
+    //function for pushing the element 
+    void push()
     {
-        field[i] = i;
-        push((field + i));  // HERE
+        printf("\nenter the value to insert");
+        scanf("%d",&n);
+        top=top+1;
+        a[top]=n;
     }
-
-    /* pops the elements from the stack and print that out.*/
-    for (i = 0; i < MAX; i++)
+    //function for poping the element out
+    void pop()
     {
-        pInt = pop();   /* fetch next integer */
-       
-        printf("%d\n", *pInt); /* print value */
+        if(top==0)
+        {
+            printf("\nstack is empty");
+        }
+        else
+        {
+            int item;
+            item=a[top];
+            top=top-1;
+            printf("\npoped item is %d ",item);
+        }
     }
+    //function for peeping the element from top of the stack
+    void peep()
+    {
+        int i;
+        printf("\nenter the element position to view from top");
+        scanf("%d",&i);
+        if(top-i+1<0)
+        {
+            printf("\nunderflow condition");
+        }
+        else
+        {
+            int x;
+            x=a[top-i+1];
+            printf("\nthe %dth element from top is %d",i,x);
+        }
+    }
+    //function to update the element of stack
+    
+    void update()
+    {
+        int i,n;
+        printf("\nenter the position to update");
+        scanf("%d",&i);
+        printf("\nenter the item to insert");
+        scanf("%d",&n);
+        if(top-i+1<0)
+        {
+            printf("\nunderflow condition");
+        }
+        else
+        {
+            a[top-i+1]=n;
+        }
+    }
+    int x;
+    while(1)
+    {
+        printf("\n1.push");
+        printf("\n2.pop");
+        printf("\n3.peep");
+        printf("\n4.update");
+        printf("\nenter your choice");
+        scanf("%d",&x);
+        switch(x)
+        {
+        case 1:
+            push();
+            break;
+        case 2:
+            pop();
+            break;
+        case 3:
+            peep();
+            break;
+        case 4:
+            update();
+            break;
+        default:
+            printf("\ninvalid choice");
+        }
+    }
+    return(0);
+}
 
-   
-
-    return EXIT_SUCCESS;
-}