CMSC 160 Fall 2018
 09/06/2018 Exploring Loops Due:  end of lab

### Handin

You may work in groups of up to 3.  If so, hand in only ONE submission sheet.    It will be assumed that all members of the group participated.

### Assignment:    (3 points)

For each of the following snippets:
1. Try to predict what it does
2. Type the code in to a program, run it and see if you were right.
3. If you were wrong, understand what happened.  Ask questions as necessary.

 1 int x = 0; while (x < 5) {     cout << "Thursday" << endl;     ++x ; } int x = 0; while (x < 5) {     ++x;     cout << "Thursday" << endl; } int x = 0; while (x < 5) {     cout << "Thursday" << endl; } 2 int x = 0; while (x < 5) {     x = x + 1;     cout << "Great Lab" << endl; } int x = 0; while (x < 5)     cout << "Great Lab" << endl;     x = x + 1; int x = 0; while (x < 5)     ++x;     cout << "Great Lab" << endl; 3 For each of the snippets in rows 1 and 2, change the 5 to be 10. What will happen differently? 4 int y = 0; while (y < 5) {     cout << y << endl;     ++y; } int y = 0; while (y < 5) {     ++y;     cout << y << endl; } int y = 0; while (y < 5) {     y = y + 1;     cout << y << endl; } 5 int x = 6; while (x < 19) {     cout << "Great Lab" << endl;     ++x; } int x = 153; while (x < 162) {     cout << "Great Lab" << endl;     ++x; } int x = 13; while (x < 21) {     cout << "Great Lab" << endl;     cout << x << endl;     x = x + 1; } cout << x << endl; 6 int x = 0; while (x < 5) {     cout << x << endl;     --x; } int x = 5; while (x >0) {     cout << "Great Lab";     cout << x << endl;     --x; } cout << x << endl; int x = 5; while (x >=0) {     cout << "Great Lab" << endl;     --x; } cout << x << endl; 7 int a = 10; int b = 20; while (a < b) {     a = a + 1;     cout << "Great Lab" << endl;     b = b - 1;     cout << a << "  " << b << endl; } cout << a << "  " << b << endl; int a = 11; int b = 20; while (a < b) {     a = a + 1;     cout << "Great Lab" << endl;     b = b - 1;     cout << a << "  " << b << endl; } cout << a << "  " << b << endl; int a = 11; int b = 20; while (a < b) {     a = a + 1;     cout << "Great Lab" << endl;     if (b > 18)         b = b - 1;     cout << a << "  " << b << endl; } cout << a << "  " << b << endl; 8 int x = 10; int y = 50; while ((x < 15) and (y <58 )) {     x = x + 1;     y = y + 1;     cout << "Weekend coming" << endl;     cout << x << "  " << y << endl; } cout << x << "  " << y << endl; int x = 10; int y = 50; while ((x < 15) and (y <58 )) {     x ++;     y ++;     cout << "Weekend coming" << endl;     cout << x << "  " << y << endl; } cout << x << "  " << y << endl; int x = 10; int y = 50; while ((x < 15) or (y <58 )) {     x = x + 1;     y = y + 1;     cout << "Weekend coming" << endl;     cout << x << "  " << y << endl; } cout << x << "  " << y << endl; 9 int x = 10; int y = 50; while ((x < 15) and (y <58 )) {     x ++;     cout << "Weekend coming";     cout << x << endl; } cout << x << endl; int x = 10; while (x < 20) {     cout << "Weekend coming" ;     cout << x << endl;     x = x + 2; } cout << x << endl; int x = 10; while (x < 100) {     cout << "Weekend coming";     cout << x << endl;     x = x * 2; }  cout << x << endl;

10)
Write a program that asks the user to enter a number.  After the user has entered a number, the word "Hello" should appear on screen that many times.
Sample:
 Enter a number:   7 Hello Hello Hello Hello Hello Hello Hello Enter a number:   3 Hello Hello Hello

GET YOUR PROGRAM TO WORK ON THE COMPUTUER.   Then, write your code on the back of the lab sheet.

### PRACTICE:

These are for practice and not to be turned in.

a)  Modify program from number 10 that if the user types in a negative number they are re-prompted until they type in a positive number.  THEN, "hello" gets printed on screen that many times.

b)  Write a program that asks the user to enter the purchase price of an item, and the amount tendered.    IF the amount tendered is less than the purchase price, let them enter a new number.    The program should repeat asking them for new numbers until the amount paid is high enough.  However, the program should not let them try more than 5 times.

c) Write a program that writes the numbers 1-50 on the screen.   However, the numbers 1-10 s hould be in the first column, 11-20 in the next column, ... 41-50 in the fifth column.

d)  Write a program that asks the user for 20 numbers and reports their average to the screen.

e)
• Write a prgoram that calculates the sum of the numbers 1 through 100.
• Write a program that calculates the sum of all even numbers between 1 and 1000 (inclusive).