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Loops Lesson 4

Loops Lesson 4. Objectives. for loop while loop do-while loop. for loop Syntax. for (begin point; end point ; incrementation ) { //statements to be repeated }. for loop Example. for (c = 0; c &lt; 10 ; c++ ) { cout &lt;&lt; “You get no bull from this Kow <br>”;

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Loops Lesson 4

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  1. LoopsLesson 4

  2. Objectives • for loop • while loop • do-while loop

  3. for loop Syntax for (begin point; end point ; incrementation ) { //statements to be repeated }

  4. for loop Example for (c = 0; c < 10 ; c++ ) { cout << “You get no bull from this Kow\n”; }

  5. while loop Syntax while ( condition ) { //statements to be repeated }

  6. while loop Example int x = 1; while ( x < 10 ) { cout << x << “ “ << x*x << “\n”; x = x +1; }

  7. do - while loop Syntax do { //statements to be repeated } while ( condition );

  8. do - while loop Example float inch = 1.0; do { cout << inch << “ inch = “ << inch * 2.54 << “ cm\n”; inch = inch + 1.0; } while ( inch < 10 );

  9. Program with Loops Read in a line of text followed by a return. Count the number of characters in the line. Repeat steps 1 & 2 as many times as the user desires.

  10. again Flowchart Promt for sentence Initialize length to 0 Read char. into ch ch != ‘\n’ Increment length by 1 Read next char. into ch ch Print length of text Prompt and read into again again == ‘y’

  11. Code do { cout << "Type sentence & press <enter>." << " I'll tell you length" << endl; lenth = 0; cin.get(ch); // "primes" the loop while (ch != '\n') { length++; cin.get(ch); } cout << endl << "Your sentence is " << length << " characters long.\n" << endl; cout << "More input ?? "; cin >> again; cin.ignore(); } while (again == 'y'); return 0; } #include <iostream> using std::cin; using std::cout; using std::endl; int main() { char ch, again; int length;

  12. Code- Part 1 #include <iostream> using std::cin; using std::cout; using std::endl; int main() { char ch, again; int length;

  13. Nested Loops do { cout << "Type sentence & press <enter>." << " I'll tell you length" << endl; length = 0; cin.get(ch); // "primes" the loop while (ch != '\n') { length++; cin.get(ch); } cout << endl << "Your sentence is " << length << " characters long.\n" << endl; cout << "More input ?? "; cin >> again; cin.ignore(); } while (again == 'y'); return 0; }

  14. Priming Read do { cout << "Type sentence & press <enter>." << " I'll tell you length" << endl; length = 0; cin.get(ch); // "primes" the loop while (ch != '\n') { length++; cin.get(ch); } cout << endl << "Your sentence is " << length << " characters long.\n" << endl; cout << "More input ?? "; cin >> again; cin.ignore(); } while (again == 'y'); return 0; }

  15. Inner while loop do { cout << "Type sentence & press <enter>." << " I'll tell you length" << endl; lenth = 0; cin.get(ch); // "primes" the loop while (ch != '\n') { length++; cin.get(ch); } cout << endl << "Your sentence is " << length << " characters long.\n" << endl; cout << "More input ?? "; cin >> again; cin.ignore(); } while (again == 'y'); return 0; }

  16. Outside while loop do { cout << "Type sentence & press <enter>." << " I'll tell you length" << endl; lenth = 0; cin.get(ch); // "primes" the loop while (ch != '\n') { length++; cin.get(ch); } cout << endl << "Your sentence is " << length << " characters long.\n" << endl; cout << "More input ?? "; cin >> again; cin.ignore(); } while (again == 'y'); return 0; }

  17. Repeating the Program do { cout << "Type sentence & press <enter>." << " I'll tell you length" << endl; lenth = 0; cin.get(ch); // "primes" the loop while (ch != '\n') { length++; cin.get(ch); } cout << endl << "Your sentence is " << length << " characters long.\n" << endl; cout << "More input ?? "; cin >> again; cin.ignore(); } while (again == 'y'); return 0; }

  18. do while Loop do { cout << "Type sentence & press <enter>." << " I'll tell you length" << endl; lenth = 0; cin.get(ch); // "primes" the loop while (ch != '\n') { length++; cin.get(ch); } cout << endl << "Your sentence is " << length << " characters long.\n" << endl; cout << "More input ?? "; cin >> again; cin.ignore(); } while (again == 'y'); return 0; }

  19. cin.ignore ( ) do { cout << "Type sentence & press <enter>." << " I'll tell you length" << endl; lenth = 0; cin.get(ch); // "primes" the loop while (ch != '\n') { length++; cin.get(ch); } cout << endl << "Your sentence is " << length << " characters long.\n" << endl; cout << "More input ?? "; cin >> again; cin.ignore(); } while (again == 'y'); return 0; }

  20. Reason for Different Types of Loops A for loop is generally used when you know how many times you want to repeat a section of code. When you don’t know how many times you want to repeat a section of code but you want to specify a condition in which the code is to be repeated , use a while or a do-while loop. A do-while loop is used when you want the code to be executed at least once. In a do-while, the test is done at the end of the loop In a while loop , the condition is checked at the beginning of the loop. If the condition is false, the body of the loop will never be executed.

  21. Summary • for loop • while loop • do-while loop

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