Superior University. Department of Electrical Engineering CS-115. Computing Fundamentals. Experiment No.5. for loop and do-while loop

Transcription

1 Superior University Department of Electrical Engineering CS-115 Computing Fundamentals Experiment No.5 for loop and do-while loop Prepared for By: Name: ID: Section: Semester: Total Marks: Obtained Marks: Signature: Date:

2 Contents of Lab Objectives: Introduction:... 3 Example 1:... 4 Example 2:... 4 Example 3:... 5 Example 4:... 5 Example 5:... 5 Example 6: do...while Looping (Repetition) Structure... 6 Example 1: Lab Tasks:... 8 Task 1:... 8 Task 2:... 8 Task 3:... 8 Task 4: Home Assignment:... 9 Task 1:... 9 Task 2:... 9 Task 3: Engr. Syed Intazar Hyder

3 For loop and de-while loop 5.1. Objectives: To get basic understanding repetition looping using for loop. To practice how to use for loop. To get basic understanding repetition looping using do-while loop. To practice how to use do-while loop Introduction: The for loop is typically called a counted or indexed for loop. The general form of the for statement is: The initial statement, loop condition, and update statement (called for loop control statements) enclosed within the parentheses control the body (statement) of the for statement. The for loop executes as follows: 1. The initial statement executes. 2. The loop condition is evaluated. If the loop condition evaluates to true: i. Execute the for loop statement. ii. Execute the update statement (the third expression in the parentheses). 3. Repeat Step 2 until the loop condition evaluates to false. The initial statement usually initializes a variable (called the for loop control, or for indexed, variable). 3 Engr. Syed Intazar Hyder

4 Example 1: 1 // Lab_5_Example_1_for loop 2 #include<iostream> 3 using namespace std; 4 int main() 5 6 int counter; 7 for (counter=0; counter<=5; counter++) 8 cout<<counter; 9 // for (counter=0; counter<=5; counter+=1) 10 // line 7 can also be written as line 9 11 return 0; The initial statement, counter = 0;, initializes the int variable counter to 0. Next, the loop condition, counter < =5, is evaluated. Because 0 < =5 is true, the print statement executes and outputs 0. The update statement, counter++, then executes, which sets the value of i to 1. Once again, the loop condition is evaluated, which is still true, and so on. When counter becomes 5, the loop condition evaluates to false, the for loop terminates, and the statement following the for loop executes. Example 2: // Lab_5_Example_2_for loop #include<iostream> using namespace std; int main() int i; for (i=0; i<=5; i++) cout<<"welcome to class"<<"\n"; cout<<"*"; return 0; This loop outputs Hello! five times and the star only once. Note that the for loop controls only the first output statement because the two output statements are not made into a compound statement. Therefore, the first output statement executes five times because the for loop body executes five times. After the for loop executes, the second output statement executes only once. The indentation, which is ignored by the compiler, is nevertheless misleading. 4 Engr. Syed Intazar Hyder

5 Example 3: // Lab_5_Example_3_for loop #include<iostream> using namespace std; int main() int i; for (i=0; i<=5; i++) cout<<"welcome to class"<<"\n"; cout<<" * "; return 0; The following for loop outputs Hello! and a star (on separate lines) five times: Example 4: Execute the following programs and write the results in column. for (i = 10; i <= 9; i++) cout << endl; Example 5: for (i = 9; i >= 10; i--) cout << endl; Example 6: for (i = 10; i <= 10; i++) cout << endl; 5 Engr. Syed Intazar Hyder

6 5.3. do...while Looping (Repetition) Structure This section describes the third type of looping or repetition structure, called a do...while loop. The general form of a do...while statement is as follows: statement can be either a simple or compound statement. If it is a compound statement, enclose it between braces. The flow of execution of a do...while loop given below. Example 1: // Lab_5_Example_1_do...while loop #include<iostream> using namespace std; int main() int i; i = 0; do i = i + 5; while (i <= 20); return 0; 6 Engr. Syed Intazar Hyder

7 Consider the following two loops: a) i = 11; while (i <= 10) i = i + 5; cout << endl; b) i = 11; do i = i + 5; while (i <= 10); cout << endl; In (a), the while loop produces nothing. In (b), the do...while loop outputs the number 11 and also changes the value of i to 16. // Lab_5_Example_1_do...while loop #include<iostream> using namespace std; int main() int i; i = 0; do i = i + 5; while (i <= 20); return 0; 7 Engr. Syed Intazar Hyder

8 5.4. Lab Tasks: Task 1: Write a program to construct the table. It prompts user to enter the number for which user wants to get table. Do program by for loop Task 2: Write a program which takes a single integer argument "height" and displays a "pyramid" of this height made up of "*" characters on the screen. Test the function with a simple "driver" program, which should be able to reproduce the following example output: Task 3: Write a program that prints the following diamond shape. You may use output statements that print a single asterisk (*), a single blank or a single newline. Maximize your use of repetition (with nested for statements) and minimize then, umber of output statements. Task 4: Write a program that uses while loops to perform the following steps: a) Prompt the user to input two integers: firstnum and secondnum (firstnum must be less than secondnum). b) Output all odd numbers between firstnum and secondnum. c) Output the sum of all even numbers between firstnum and secondnum. d) Output the numbers and their squares between 1 and 10. e) Output the sum of the square of the odd numbers between firstnum and secondnum. f) Output all uppercase letters. Do program using do while loop 8 Engr. Syed Intazar Hyder

9 5.5. Home Assignment: Task 1: Write a program that uses while loops to perform the following steps: a) Prompt the user to input two integers: firstnum and secondnum (firstnum must be less than secondnum). b) Output all odd numbers between firstnum and secondnum. c) Output the sum of all even numbers between firstnum and secondnum. d) Output the numbers and their squares between 1 and 10. e) Output the sum of the square of the odd numbers between firstnum and secondnum. f) Output all uppercase letters. Do program using for loop Task 2: (Drawing Patterns with Nested for Loops) Write a program that uses for statements to print the following patterns separately, one below the other. Use for loops to generate the patterns. All asterisks (*) should be printed by a single statement of the form cout << '*'; (this causes the asterisks to print side by side). [Hint: The last two patterns require that each line begin with an appropriate number of blanks. Extra credit: Combine your code from the four separate problems into a single program that prints all four patterns side by side by making clever use of nested for loops.] a) b) c) d) Task 3: A high school has 1000 students and 1000 lockers, one locker for each student. On the first day of school, the principal plays the following game: She asks the first student to go and open all the lockers. She then asks the second student to go and close all the even-numbered lockers. The third student is asked to check every third locker. 9 Engr. Syed Intazar Hyder

10 If it is open, the student closes it; if it is closed, the student opens it. The fourth student is asked to check every fourth locker. If it is open, the student closes it; if it is closed, the student opens it. The remaining students continue this game. In general, the nth student checks every nth locker. If the locker is open, the student closes it; if it is closed, the student opens it. After all the students have taken their turn, some of the lockers are open and some are closed. Write a program that prompts the user to enter the number of lockers in a school. After the game is over, the program outputs the number of lockers that are opened. Test run your program for the following inputs: 1000, 5000, Do you see any pattern developing? (Hint: Consider locker number 100. This locker is visited by student numbers 1, 2, 4, 5, 10, 20, 25, 50, and 100. These are the positive divisors of 100. Similarly, locker number 30 is visited by student numbers 1, 2, 3, 5, 6, 10, 15, and 30. Notice that if the number of positive divisors of a locker number is odd, then at the end of the game, the locker is opened. If the number of positive divisors of a locker number is even, then at the end of the game, the locker is closed.) 10 Engr. Syed Intazar Hyder