diff --git a/c/1darray.c b/c/1darray.c
index c7faaf0..173f8d4 100644
--- a/c/1darray.c
+++ b/c/1darray.c
@@ -14,4 +14,4 @@ int main(){
 
 	printf("Sum=%d",sum);
 	return 0;
-}
\ No newline at end of file
+}
diff --git a/c/2darray.c b/c/2darray.c
index 0a2bf8b..cb4fcf5 100644
--- a/c/2darray.c
+++ b/c/2darray.c
@@ -20,4 +20,4 @@ int main(){
 		}
 	}
 	return 0;
-}
\ No newline at end of file
+}
diff --git a/c/a.out b/c/a.out
new file mode 100755
index 0000000..e8f984d
Binary files /dev/null and b/c/a.out differ
diff --git a/c/callByRef.c b/c/callByRef.c
index 3115dc1..10955b2 100644
--- a/c/callByRef.c
+++ b/c/callByRef.c
@@ -32,4 +32,4 @@ void callByRef(int *x,int *y){
 	*y=*t;
 	printf("From call by value\n");
 	printf("x=%d\ty=%d\n",*x,*y);
-}
\ No newline at end of file
+}
diff --git a/c/cylinder.c b/c/cylinder.c
index 55bda34..fdb7375 100644
--- a/c/cylinder.c
+++ b/c/cylinder.c
@@ -33,4 +33,4 @@ void cylinder(float r, float h, float *csa, float *tsa, float *vol){
 	*csa = 2*r*h*PI;
 	*tsa = 2*r*(h+r)*PI;
 	*vol = r*r*h*PI;
-}
\ No newline at end of file
+}
diff --git a/c/datatype.c b/c/datatype.c
index 6813326..0fbc42f 100644
--- a/c/datatype.c
+++ b/c/datatype.c
@@ -12,4 +12,4 @@ int main(){
 	//printing data
 	printf("%c %d %f %lf",ch,i,f,d);
 	return 0;
-}
\ No newline at end of file
+}
diff --git a/c/empstruct.c b/c/empstruct.c
index 9b53542..0ba5cab 100644
--- a/c/empstruct.c
+++ b/c/empstruct.c
@@ -37,4 +37,4 @@ int main(){
 	printf("\nHighest Earner Detail\n");
 	printf("Name: %s\nPost: %s\nSalary: %.2f\n",high.name,high.post,high.salary);
 	return 0;
-}
\ No newline at end of file
+}
diff --git a/c/forloop.c b/c/forloop.c
index 79bce71..e6feae5 100644
--- a/c/forloop.c
+++ b/c/forloop.c
@@ -4,6 +4,7 @@ int main(){
 	int i,n;
 
 	//reading value of n
+	printf("Enter n: ");
 	scanf("%d",&n);
 
 	//for loop
@@ -11,4 +12,4 @@ int main(){
 		printf("%d\n",i);
 	}
 	return 0;
-}
\ No newline at end of file
+}
diff --git a/c/hello.c b/c/hello.c
index cf363a5..bc71556 100644
--- a/c/hello.c
+++ b/c/hello.c
@@ -2,4 +2,4 @@
 int main(){
 	printf("Hello World");
 	return 0;
-}
\ No newline at end of file
+}
diff --git a/recursion/a.out b/recursion/a.out
new file mode 100755
index 0000000..b54f1c1
Binary files /dev/null and b/recursion/a.out differ
diff --git a/recursion/gcd.c b/recursion/gcd.c
index cf94b58..77b3f10 100644
--- a/recursion/gcd.c
+++ b/recursion/gcd.c
@@ -1,8 +1,12 @@
 #include <stdio.h>
+
+//recursive function for gcd of two numbers.
 int gcd(int x, int y);
 
+//iterative function for gcd of two numbers.
+int gcd_iter(int u , int v);
 int main(){
-	int a, b, g;
+	int a, b, g, f;
 
 	printf("Enter a and b:\n");
 	scanf("%d%d", &a, &b);
@@ -10,17 +14,37 @@ int main(){
 	//gcd
 	g = gcd(a, b);
 
+	//gcd_iter
+	f=gcd_iter(a, b);
+
 	//in case g is negative, then convert it into positive
 	if(g < 0){
 		g *= -1;
 	}
 
+	//in case f is negative, then convert it into positive
+	if(f < 0){
+		f=f*(-1);
+	}
+
 	//output
-	printf("GCD(%d, %d) = %d\n", a, b, g);
+	printf("Recursive GCD(%d, %d) = %d\n", a, b, g);
+	printf("Iterative GCD(%d, %d) = %d\n", a, b, f);
 	return 0;
 }
 
 int gcd(int x, int y){
 	if(y == 0) return x;
 	else gcd(y, x%y);
-}
\ No newline at end of file
+}
+
+
+int gcd_iter(int u, int v){
+	int t;
+	while (v) {
+		t = u; 
+		u = v; 
+		v = t % v;
+	}
+	return u < 0 ? -u : u; /* abs(u) */
+}
diff --git a/recursion/towerOfHanoi.c b/recursion/towerOfHanoi.c
index 6274d89..15850e3 100644
--- a/recursion/towerOfHanoi.c
+++ b/recursion/towerOfHanoi.c
@@ -19,4 +19,4 @@ void t(int n, char beg, char aux, char end){
 		t(1, beg, aux, end);
 		t(n-1, aux, beg, end);
 	}
-}//t() ends here
\ No newline at end of file
+}//t() ends here