diff --git a/Class711.cpp b/Class711.cpp
new file mode 100755
index 0000000..80d9bc1
--- /dev/null
+++ b/Class711.cpp
@@ -0,0 +1,61 @@
+//============================================================================
+// Name        : Classroom1.cpp
+// Author      : 
+// Version     :
+// Copyright   : Your copyright notice
+// Description : Hello World in C++, Ansi-style
+//============================================================================
+
+#include <iostream>
+using namespace std;
+
+int mypower(int n, int i) {
+
+	if (i < 0) {
+		return -1;
+	}
+
+	int result = 1;
+
+	while (i > 0) {
+
+		result = n * result; //result *= n
+
+		i--;
+	}
+
+	return result;
+}
+
+int square(int n) {
+
+	return n * n;
+
+}
+
+int main() {
+
+	int val = mypower(2, -4);
+
+	if (val < 0) {
+		cout << "Error"<< endl;
+
+	} else {
+		cout << "Result " << val << endl;
+	}
+
+	cout << "2 ** -4   " << mypower(2, -4) << endl;
+//	cout << "5 ** 0   " << mypower(5, 0) << endl;
+
+/*	int cnt = 1;
+
+	while (cnt <= 10) {
+
+		cout << cnt << "  " << square(cnt) << endl;
+		cnt = cnt + 1; //cnt += 1 or cnt++
+	}
+*/
+	return 0;
+
+
+}
diff --git a/Class712.cpp b/Class712.cpp
new file mode 100755
index 0000000..ec32c60
--- /dev/null
+++ b/Class712.cpp
@@ -0,0 +1,67 @@
+//============================================================================
+// Name        : Class712.cpp
+// Author      : 
+// Version     :
+// Copyright   : Your copyright notice
+// Description : Hello World in C++, Ansi-style
+//============================================================================
+
+#include <iostream>
+using namespace std;
+
+int sum(int n) {
+
+	int total = 0;
+
+	//Version 1 -- loop
+//	for (int i = 1; i <= n; i++) {
+//		total += i;
+//	}
+	while (n > 0) {
+		total += n;
+		n--;
+	}
+
+	//Version 2 -- closed form
+	//total = n * (n + 1) / 2; //watch out for integer division
+
+	//Version 3 -- recursion
+//	if (n == 0) {
+//		return 0;
+//	} else {
+//		total = sum(n-1) + n;
+//		return total;
+//	}
+
+	return total;
+}
+
+
+int main() {
+
+	int val;
+
+	do {
+		cout << "Enter (neg to stop): ";
+		cin >> val;
+
+		if (val < 0) break;
+
+		cout << "val: " << val << endl;
+		cout << "Result: " << sum(val) << endl << endl;
+		cout << "val: " << val << endl;
+		/*
+		 * The call-by-value parameter passing mechanism is used
+		 * when calling the sum function. Consequently, the value of
+		 * the variable 'val' does not change, even the corresponding
+		 * parameter 'n' in the function is modified.
+		 */
+
+//		if (val >= 0) {
+//			cout << "Result: " << sum(val) << endl << endl;
+//		}
+
+	} while (true);// (val >= 0);
+
+	return 0;
+}
diff --git a/Class713.cpp b/Class713.cpp
new file mode 100755
index 0000000..2deede5
--- /dev/null
+++ b/Class713.cpp
@@ -0,0 +1,133 @@
+//============================================================================
+// Name        : Class713.cpp
+// Author      : 
+// Version     :
+// Copyright   : Your copyright notice
+// Description : Hello World in C++, Ansi-style
+//============================================================================
+
+#include <math.h>
+#include <string>
+#include <iostream>
+using namespace std;
+
+#define PI 3.14159265
+
+void sample1( ) {
+	double degree, result;
+	degree = 60.0;
+
+	result = cos (degree * PI/180);
+
+	cout << result << endl;
+
+	return;
+}
+
+void string1( ) {
+
+	string str;
+	int n;
+
+	n = 10;
+	str = "Hello";
+	string space = "";
+
+	for (int i = 0; i < 10; i++) {
+
+		space += "  ";
+
+		cout << space << str << endl;
+        //	cout << str << " " << i << endl;
+	}
+
+	return;
+}
+
+void string2 ( ) {
+
+	string first, last;
+
+	first = "John";
+	last = "Smith";
+
+	string fullname1 = first + " " + last; //John Smith
+	string fullname2 = last + ", " + first; //Smith, John
+	cout << fullname1 << endl << fullname2 << endl;
+
+	string fullname3 = "";
+
+//	fullname3 = first[0];
+//	fullname3 = fullname3 + ". " + last;
+
+
+	fullname3.append(1, first[0]); //change 1 to 3 and see what happens
+	fullname3.append(". " + last);
+    //or
+    //fullname3 = fullname3 + ". " + last;
+
+	cout << fullname3 << endl;
+
+    /*
+     Note:
+
+     We cannot the string concatenation operation as
+
+            string s = first[0] + ". " + last;
+
+     because of data type mismatch. Expression first[0] is char, not string
+     */
+
+	return;
+}
+
+void string3( ) {
+
+    cout << endl << endl;
+
+    string str = "This is a test";
+
+    cout << "'" << str << "' has " << str.size() << " characters." << endl;
+    cout << str.substr(0,4) << endl;
+    cout << "First blank space in the string at position " << str.find(" ") << endl;
+    cout << str << endl;
+
+    return;
+}
+
+void string4( ) {
+	//find the number of blank spaces in a given string
+	string str = "Hello world how  are you  .";
+
+	string searchStr = " ";
+
+	int cnt = 0;
+	int loc = str.find(searchStr);
+
+	while (loc >= 0) { /*not found*/
+
+		cnt++;
+
+		str = str.substr(loc+1,str.size( ));
+		loc = str.find(searchStr);
+	}
+
+	cout << cnt << endl;
+
+	return;
+}
+
+int main() {
+
+	//sample1( );
+
+	//string1( );
+
+	//string2( );
+
+    //string3( );
+
+	string4();
+
+	return 0;
+}
diff --git a/Class715.cpp b/Class715.cpp
new file mode 100755
index 0000000..78996fd
--- /dev/null
+++ b/Class715.cpp
@@ -0,0 +1,196 @@
+//============================================================================
+// Name        : Class715.cpp
+// Author      : 
+// Version     :
+// Copyright   : Your copyright notice
+// Description : Hello World in C++, Ansi-style
+//============================================================================
+
+#include <math.h>
+#include <string>
+#include <iostream>
+using namespace std;
+
+void practice1_Step1() {
+
+	const float DEG_TO_RADIAN = 3.14159 / 180.0;
+	float dist, height, alpha, beta;
+
+	cout << "Enter distance between points A and B: ";
+	cin >> dist;
+
+	cout << "Enter degree alpha: ";
+	cin >> alpha;
+
+	cout << "Enter degree beta: ";
+	cin >> beta;
+
+	height = 150;
+
+	cout << "distance: " << dist << endl;
+	cout << "alpha:    " << alpha << endl;
+	cout << "beta:     " << beta  << endl << endl;
+	cout << "height:   " << height << endl;
+
+}
+
+/*
+ * d - distance between A and B
+ * a - angle A in radian
+ * b - angle B in radian
+ *
+ * return h - height = d * sin(a) * sin(b) / sqrt(sin(a + b) * sin(a-b))
+ */
+float computeHeight(float d, float a, float b) {
+		//Note: Pass values such that a > b?
+	float h;
+
+	//h = 150.0; //test value to check the function before
+				//writing a full implementation
+
+	h = d * sin(a) * sin(b) / sqrt(sin(a+b) * sin(a-b));
+
+	//test outputs
+//	cout << sin(a) <<  endl;
+//	cout << sin(b) << endl;
+//	cout << sin(a+b) << endl;
+//	cout << sin(a-b) << endl;
+
+	return h;
+}
+
+void practice1_Step2(){
+
+	const float DEG_TO_RADIAN = 3.14159 / 180.0;
+	float dist, height, alpha, beta;
+
+	cout << "Enter distance between points A and B: ";
+	cin >> dist;
+
+	cout << "Enter degree alpha: ";
+	cin >> alpha;
+
+	cout << "Enter degree beta: ";
+	cin >> beta;
+
+	height = computeHeight(dist, alpha * DEG_TO_RADIAN, beta * DEG_TO_RADIAN);
+
+	cout << "distance: " << dist << endl;
+	cout << "alpha:    " << alpha << endl;
+	cout << "beta:     " << beta  << endl << endl;
+	cout << "height:   " << height << endl;
+}
+
+/*
+ * Count how many times string c occurs in string s
+ */
+int search(string s, string c) {
+	int result = 0;
+
+	int loc = 0;
+
+	while (true) {
+
+		loc = s.find(c, loc); //start looking for c in s from loc
+
+		if (loc < 0) break;
+
+		result++;
+		loc++;
+	}
+
+	return result;
+}
+/*
+ * Scan the string multiple times. Each scan will detect
+ * the number of occurrence of a specified vowel.
+ */
+void practice2Ver1() {
+
+	string str;
+
+	/*
+	 * NOTE: The following input routine does not work as normally expected.
+	 * 		 Variable 'str' is terminated by a blank space so if you enter
+	 *
+	 * 		 This is a test
+	 *
+	 * 		 the text 'This' is assigned to str.
+	 *
+	 * 		 You need to use the getline function to read the complete string,
+	 * 		 up to the RETURN key press.
+	 */
+//	cout << "Enter String: " ;
+//	cin >> str;
+
+	cout << "Enter string: ";
+	getline(cin, str); //input full line
+
+	int cnt = 0;
+
+	cnt += search(str, "a");
+	cnt += search(str, "e");
+	cnt += search(str, "i");
+	cnt += search(str, "o");
+	cnt += search(str, "u");
+
+	cout << "Vowel Cnt: " << cnt;
+}
+
+/*
+ * In this version, we scan the string only once. For each character we
+ * process, we test if it is a lowercase vowel and increment the vowel
+ * counter accordingly.
+ */
+void practice2Ver2(){
+
+	string str;
+
+	cout << "Enter string: ";
+	getline(cin, str); //input full line
+
+	int cnt = 0;
+
+	for (int loc = 0; loc < str.size(); loc++) {
+		char ch = str[loc];
+							//NOTE: char constant is single quote
+		if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
+			cnt++;
+		}
+	}
+
+	cout << "Vowel Cnt: " << cnt;
+}
+
+
+int main() {
+
+	/*
+	 * Implement this exercise in 2 steps. In Step 1 we implement
+	 * input and output routines using a fixed (dummy) output. Once
+	 * we confirm the routines work okay, then we implement the
+	 * computation routine. Two steps are written in two separate
+	 * functions to illustrate the development steps. In practice,
+	 * you write the first step and then add or modify code to the
+	 * existing code.
+	 */
+	//practice1_Step1();
+	//practice1_Step2();
+
+	/*
+	 * Count the number of lowercase vowels in a given string str.
+	 * There are two (perhaps more) approaches. Approach 1 is to scan
+	 * the string for a specific character. We are looking for
+	 * five specific characters (a, e, i, o, & u) so we scan
+	 * the string fives, one for each vowel. Approach 2 is to scan
+	 * the string exactly once. For each character in the string,
+	 * check if this character is a vowel.
+	 *
+	 * Again you should develop the functions in incremental steps. Here
+	 * we provide only the final version.
+	 */
+	//practice2Ver1();
+	practice2Ver2();
+
+	return 0;
+}
diff --git a/Class718.cpp b/Class718.cpp
new file mode 100755
index 0000000..e3b82c3
--- /dev/null
+++ b/Class718.cpp
@@ -0,0 +1,143 @@
+//============================================================================
+// Name        : Class718.cpp
+// Author      : 
+// Version     :
+// Copyright   : Your copyright notice
+// Description : Hello World in C++, Ansi-style
+//============================================================================
+
+#include <iostream>
+using namespace std;
+
+void sample1(){
+	//Compute the average of given input values -- 0 to terminate
+	double val, sum, avg;
+	int cnt;
+
+	sum = 0.0;
+	cnt = 0;
+
+	do {
+		cout << "Enter value (0 to terminate): ";
+		cin >> val;
+
+		if (val == 0) break;
+
+		cnt++;
+		sum += val;
+
+	} while (true);
+
+	avg = sum / cnt;
+
+	cout << endl << "Average: " << avg << endl;
+}
+
+void sample2(){
+
+	//compute the average of given input values
+	//determine the number of values less than average and those
+	//greater than average
+
+	//KEY POINT: I need to REMEMBER the input values
+
+	double number[100]; //static declaration and allocation
+
+	double val, sum, avg;
+	int cnt, belowAvgCnt, aboveAvgCnt;
+
+	sum = 0.0;
+	cnt = belowAvgCnt = aboveAvgCnt = 0;
+
+	do {
+		cout << "Enter value (0 to terminate): ";
+		cin >> val;
+
+		if (val == 0) break;
+
+		number[cnt] = val;
+
+		cnt++;
+		sum += val;
+
+	} while (true); //NOTE: This loop will crash if someone tries to enter more than 100 numbers
+
+	avg = sum / cnt;
+
+	for (int i = 0; i < cnt; i++) {
+		if (number[i] < avg) {
+			belowAvgCnt++;
+		} else if (number[i] > avg) {
+			aboveAvgCnt++;
+		}
+	}
+
+	cout << endl << "Average: " << avg << endl;
+	cout << "Below Average Cnt: " << belowAvgCnt << endl;
+	cout << "Above Average Cnt: " << aboveAvgCnt << endl;
+
+}
+
+int sum(int collection[ ], int size) {
+
+	int total = 0;
+
+	for (int i = 0; i < size; i++ ) {
+		total += collection[i];
+	}
+
+	return total;
+}
+
+void sample3(){
+
+	//Passing an array to a function
+
+	//static initialization of arrays
+	int arr1[ ] = {1, 4, -5, 8, 6, 9, 19};
+//	int arr1[7];
+//	arr1[0] = 1;
+//	arr1[1] = 4;
+	//...
+
+	int arr2[ ] = {10, 8, 6, 4, 2, 0,  -2, -4, -6, -8, -10};
+
+	cout << "Sum 1: " << sum(arr1, 7) << endl;
+	cout << "Sum 2: " << sum(arr2, 11) << endl;
+}
+
+void sample4() {
+
+	int mylist[ ] = {10, 8, 6, 4, 2, 0,  1, 3, 5, 7, 9};
+
+	int sum1 = 0;
+	for (int i = 0; i < 11; i++) { //sum of even integers
+		if (mylist[i] % 2 == 0) {
+			sum1 += mylist[i];
+		}
+	}
+
+	int sum2 = 0;
+	for (int j = 0; j < 11; j++) { //sum of integers in even index position
+		if (j % 2 == 0) {
+			sum2 += mylist[j];
+		}
+	}
+	cout << "Sum of even ints = " << sum1 << endl;
+	cout << "Sum of ints in even pos = " << sum2 << endl;
+	
+
+}
+
+int main() {
+
+//	sample1();
+
+//	sample2();
+
+//	sample3();
+
+	sample4();
+
+	return 0;
+}
diff --git a/Class719.cpp b/Class719.cpp
new file mode 100755
index 0000000..df279d8
--- /dev/null
+++ b/Class719.cpp
@@ -0,0 +1,126 @@
+//============================================================================
+// Name        : Class719.cpp
+// Author      : 
+// Version     :
+// Copyright   : Your copyright notice
+// Description : Hello World in C++, Ansi-style
+//============================================================================
+
+#include <iostream>
+using namespace std;
+
+//An array is a homogeneous collection of data items. In contrast
+//a struct is a heterogeneous collection of data items.
+
+struct Cat {
+	string name;
+	string breed;
+	int    age;
+	float  wgt;
+};
+
+
+void clearArray(int num[ ], int size) {
+
+	//Is an array passed by value?? Let's test
+	for (int i = 0; i < size; i++) {
+		num[i] = 0;
+	}
+
+}
+
+void sample1( ) {
+
+	int list[ ] = { 10, 20, 30, 40, 50, 60};
+
+	for (int i = 0; i < 6; i++) {
+		cout << "  " << list[i];
+	}
+
+	cout << endl;
+
+	clearArray(list, 6);
+
+	for (int i = 0; i < 6; i++) {
+		cout << "  " << list[i];
+	}
+
+	cout << endl;
+}
+
+void sample2( ) {
+
+	Cat cat1, cat2;
+
+	cat1.name = "Puff Puff";
+	cat1.breed = "Mixed";
+	cat1.age = 3;
+	cat1.wgt = 13.5;
+
+	cout << cat1.name  << endl;
+	cout << cat1.breed << endl;
+	cout << cat1.age   << endl;
+	cout << cat1.wgt   << endl;
+
+//	cout << cat1 << endl; //??
+
+	cat2 = cat1;
+
+	cout << cat2.name  << endl;
+	cout << cat2.breed << endl;
+	cout << cat2.age   << endl;
+	cout << cat2.wgt   << endl;
+
+	cat2.age += 100;
+
+	cout << cat1.age << endl;
+	cout << cat2.age << endl;
+}
+
+void happyBday(Cat cat) {
+	cat.age += 1;
+
+	cout << cat.age << endl;
+}
+
+void sample3( ) {
+
+	Cat cat1;
+
+	cat1.name = "Puff Puff";
+	cat1.breed = "Mixed";
+	cat1.age = 3;
+	cat1.wgt = 13.5;
+
+	happyBday(cat1);
+
+	cout << cat1.age << endl;
+}
+
+void sample4( ) {
+
+	//Combine two composite types array and struct into one
+	//Here's an array of struct
+	Cat myPet[10];
+
+	myPet[0].name = "Bom Bom";
+	myPet[0].breed = "Maine Coon";
+	myPet[0].age = 10;
+	myPet[0].wgt = 9.8;
+
+	//...
+}
+
+
+int main() {
+
+//	sample1( );
+
+//~ sample2( );
+
+//~ sample3( );
+
+	sample4( );
+
+	return 0;
+}
diff --git a/Class720.cpp b/Class720.cpp
new file mode 100755
index 0000000..f3dc3fe
--- /dev/null
+++ b/Class720.cpp
@@ -0,0 +1,163 @@
+//============================================================================
+// Name        : Class720.cpp
+// Author      : 
+// Version     :
+// Copyright   : Your copyright notice
+// Description : Hello World in C++, Ansi-style
+//============================================================================
+
+#include <iomanip>
+#include <iostream>
+using namespace std;
+
+
+void sample1( ) {
+
+	int*   p1;
+	int  * p2;
+	int   *p3;  //p1, p2, and p3 are all pointers to an int
+
+	int* a, b; //WATCH OUT: a is a pointer to int but b is a regular int variable
+
+	//The values of pointers are addresses so you cannot assign a data value to them directly.
+	//We need the dereferencing operator. But before we apply this operator, we need to
+	//create a memory location to store a data value.
+
+	p1 = new int; //DYNAMIC ALLOCATION, Yeah!! Now we have a box to store an int
+					//The 'new' operation returns int* an address of a newly created int box
+
+	*p1 = 45;
+
+	p2 = p1;  //Now we have two pointers referring to the same data
+
+	p3 = new int; //another box
+
+	*p3 = *p1;  //data in a box pointed by p1 is copied to another box pointed by p3
+
+	cout << *p1 << "  " << *p2 << "  " << *p3 << endl;
+
+	*p3 = 20;
+
+	cout << *p1 << "  " << *p2 << "  " << *p3 << endl;
+
+	*p1 = 50;
+
+	cout << *p1 << "  " << *p2 << "  " << *p3 << endl;
+
+}
+
+
+void sample2( ) {
+
+	int n;
+
+	int* p;
+
+	n = 100;
+
+	p = &n;  //& is the address-of operator
+
+			//at this point, p points to the int box named 'n'
+
+	cout << n << "  " << *p << endl;
+
+}
+
+void exchange1(int a, int b) {
+
+	int t = a;
+	a = b;
+	b = t;
+
+}
+
+void exchange2(int* a, int* b) {
+
+	int t;
+	t = *a;
+	*a = *b;
+	*b = t;
+
+}
+
+void sample3( ) {
+
+	int i = 10;
+	int j = 20;
+
+	exchange1(i, j);
+
+	cout << i << " " << j << endl;
+
+	int* p1;
+	int* p2;
+
+	p1 = &i; p2 = &j;
+
+	exchange2(p1, p2);
+
+	cout << *p1 << " " << *p2 << endl;
+}
+
+void clear(int list[ ], int size) { //We are actually passing a pointer to the first position of an array
+
+	for (int i = 0; i < size; i++) {
+		list[i] = 0;
+	}
+
+}
+
+void clear2(int *list, int size) {
+
+	for (int i = 0; i < size; i++) {
+			list[i] = 0;
+	}
+}
+
+void clear3(int list[], int size) {
+
+	int* p;
+
+	p = list;
+
+	int cnt = 0;
+
+	while (cnt < size) {
+
+		*p = 0;
+
+		p = p + 1;
+
+		cnt++;
+	}
+}
+
+
+void sample4( ) {
+
+	int num[ ] = {10, 20, 30, 40, 50, 60, 70, 80, 90, 100};
+
+	clear(num, 10);
+
+	clear2(num, 10);
+
+	//clear3(num, 10);
+
+	for (int i = 0; i < 10; i++) {
+		cout << "  " << num[i];
+	}
+}
+
+int main() {
+
+	sample1();
+
+	sample2();
+
+	sample3();
+
+	sample4( );
+
+
+	return 0;
+}
diff --git a/Class725.cpp b/Class725.cpp
new file mode 100755
index 0000000..fc31e2a
--- /dev/null
+++ b/Class725.cpp
@@ -0,0 +1,101 @@
+//============================================================================
+// Name        : Class725.cpp
+// Author      : 
+// Version     :
+// Copyright   : Your copyright notice
+// Description : Hello World in C++, Ansi-style
+//============================================================================
+
+//============================================================================
+// Name        : Class725.cpp
+// Author      :
+// Version     :
+// Copyright   : Your copyright notice
+// Description : Hello World in C++, Ansi-style
+//============================================================================
+
+#include <iostream>
+using namespace std;
+
+void swap(int* p, int* q) { //exchanging the two values
+
+	int t = *p;
+	*p = *q;
+	*q = t;
+}
+
+void swap2(int* p, int* q) { //this confirms that pointers are passed by value
+
+	//set p point to q's value box and
+	//q point to p's value box
+
+	int* t;
+
+	t = p;
+	p = q;
+	q = t;
+}
+
+void swap3(int& r, int& s) {
+
+	int t;
+
+	t = r;  //value box is referenced directly by the reference variable;
+	r = s;  //you don't need a deference operator like the one for the pointer variable
+	s = t;  //Reference variable is fixed; it can't change to refer to a different value box
+}
+
+void sample1() {
+
+	int* p1;
+	int* p2;
+
+	p1 = new int;
+	p2 = new int;
+
+	*p1 = 10;
+	*p2 = 20;
+
+	cout << *p1 << "  " << *p2 << endl;
+
+	swap(p1, p2);
+
+	cout << *p1 << "  " << *p2 << endl;
+
+	*p1 = 100;
+	*p2 = 200;
+
+	cout << endl;
+	cout << *p1 << "  " << *p2 << endl;
+
+	swap2(p1, p2);
+
+	cout << *p1 << "  " << *p2 << endl;
+}
+
+void sample2( ) {
+
+	//This is an example of call-by-reference
+	int n, m;
+
+	n = 10;
+	m = 20;
+
+	cout << endl;
+	cout << n << "  " << m << endl;
+
+	swap3(n, m);
+
+	cout << n << "  " << m << endl;
+}
+
+
+int main() {
+
+	sample1();
+
+	sample2();
+
+	return 0;
+}
+