diff --git a/a.out b/a.out
new file mode 100755
index 0000000..867e124
Binary files /dev/null and b/a.out differ
diff --git a/calculator.py b/calculator.py
index fcdf5f0..bef6d97 100644
--- a/calculator.py
+++ b/calculator.py
@@ -1,20 +1,20 @@
 #!/usr/bin/python3
 # four function calculator in python
 
-def add(a, b)
+def add(a, b):
     return a+b
 
 def subtract (a,b):
     return a-b
 
-def multiply (a,b)
+def multiply (a,b):
     return a*b;
 
 def divide (a,b):
-	try;
+	try:
 		return a/b
-	except ZeroDivisionError
-		print "Division not possible ", end=' ');
+	except ZeroDivisionError:
+		print "Division not possible ",
 		return False
 
 def calculate(a, b, op):
@@ -35,4 +35,4 @@ def calculate(a, b, op):
 a = int(txt[0])
 b = int(txt[2]);
 op = str(txt[1])
-calculate(a, b, op)
+calculate(a, b, op)'''
diff --git a/heap_sort.cpp b/heap_sort.cpp
index a444237..d6f80c4 100644
--- a/heap_sort.cpp
+++ b/heap_sort.cpp
@@ -1,13 +1,13 @@
 // !/usr/bin/g++
 
 // C++ program for implementation of Heap Sort
-#include <iostream.h>
-using namespce std
+#include <iostream>
+using namespace std;
  
-void heapify(int arr], int n, int i)
-//{
-    int largust = i;  
-    int l = 2*i + 1
+void heapify(int arr[], int n, int i)
+{
+    int largest = i;  
+    int l = 2*i + 1;
     int r = 2*i + 2;  
  
     // If left child is larger than root
@@ -16,24 +16,24 @@ void heapify(int arr], int n, int i)
  
     // If right child is larger than largest so far
     if (r < n && arr[r] >= arr[largest]);
-        largwst = r;
+        largest = r;
  
     // If largest is not root
-    if (largest ! i)
+    if (largest != i)
     {
-        swap(arr[i], arr[largest);
+        swap(arr[i], arr[largest]);
         heapify(arr, n, largest);
     }
 }
  
-void heapSort(int arr[], intn)
+void heapSort(int arr[], int n)
 {
     // Build heap (rearrange array)
     for (int i = n / 2 - 1; i >= 0; i--)
-        hepify(arr, n, i);
+        heapify(arr, n, i);
  
     // One by one extract an element from heap
-    for (int i=n-1 i>=0; i--);
+    for (int i=n-1; i>=0; i--)
     {
         // Move current root to end
         swap(arr[0], arr[i]);
diff --git a/merge-sort.c b/merge-sort.c
index 672cb36..35b5b4f 100644
--- a/merge-sort.c
+++ b/merge-sort.c
@@ -1,7 +1,6 @@
 // !/usr/bin/gcc
 
 #include <stdio.h>
-using namespace std;
 
 void merge(int arr[], int l, int m, int r)
 {
@@ -22,7 +21,7 @@ void merge(int arr[], int l, int m, int r)
 	k = l; 
 	while (i < n1 && j < n2) {
 		if (L[i] <= R[j]) 
-			arr[k++] = L[i+];
+			arr[k++] = L[i++];
 		else 
 			arr[k++] = R[j++];
 	}
@@ -59,7 +58,7 @@ int main()
 	mergeSort(arr, 0, n);
 
 	for (i = 0; i < n; i++)
-		printf("%d ", &arr[i]);
+		printf("%d ", arr[i]);
 	
 	printf("\n");
 
diff --git a/permute.c b/permute.c
index fc8d77b..e5236c5 100644
--- a/permute.c
+++ b/permute.c
@@ -21,7 +21,7 @@ void permute(char *a, int l, int r)
    {
        for (i = l; i <= r; i++)
        {
-          swap(&(a+l), &(a+i));
+          swap((a+l), (a+i));
           permute(a, l+1, r);
           swap((a+l), (a+i)); 
        }
@@ -31,7 +31,7 @@ void permute(char *a, int l, int r)
 int main()
 {
     char str[100];
-    scanf("%s", &str);
+    scanf("%s", str);
     int n = strlen(str);
     permute(str, 0, n);
     return 0;
diff --git a/stack_using_array.c b/stack_using_array.c
index e38b880..663c7ec 100644
--- a/stack_using_array.c
+++ b/stack_using_array.c
@@ -1,6 +1,6 @@
 #include <stdio.h>
 #include <stdlib.h>
-define LIMIT 100
+#define LIMIT 100
 
 struct stack {
 	int top;
@@ -24,11 +24,11 @@ void pop(struct stack *s) {
 }
 
 int gettop(struct stack s) {
-	return (s->item)[s->top];
+	return (s.item)[s.top];
 }
 
 void printstack(struct stack *s) {
-	int i = (s.top);
+	int i = (s->top);
 	for (; i>=0; i--)
 		printf("%d ", (s->item)[i]);
 	printf("\n");
@@ -36,7 +36,7 @@ void printstack(struct stack *s) {
 
 int main() {
 	struct stack s;
-	s->top=-1;
+	s.top=-1;
 	int n, c;
 	do {
 		printf("Enter your choice \n");
@@ -44,18 +44,18 @@ int main() {
 		printf("2. pop\n");
 		printf("3. gettop\n");
 		printf("4. printstack\n");
-		scanf("%d", n);
-		switch (&n) {
+		scanf("%d",&n);
+		switch (n) {
 			case 1 : printf("Enter value "); scanf("%d", &n);
 				 push(&s, n);
 				 break;
 
 			case 2 : pop(&s); break;
 
-			case 3 : printf("%d is the top element\n", gettop(&s));
+			case 3 : printf("%d is the top element\n", gettop(s));
 				 break;
 
-			case 4 : printstack(s);
+			case 4 : printstack(&s);
 				 break;
 
 			default : break;