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Overview. do/while loop break statement continue statement switch statement. do/while loop. do { statement; } while (condition); Step1: Execute statements inside braces Step2: Evaluate condition. Step3: If condition is true repeat Step1 through 3, otherwise

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Overview
Overview

  • do/while loop

  • break statement

  • continue statement

  • switch statement


Do while loop
do/while loop

do {

statement;

} while (condition);

Step1: Execute statements inside braces

Step2: Evaluate condition.

Step3: If condition is true repeat Step1 through 3, otherwise

continue execution at next statement following the do/while

statement

Usually use { } even when not necessary

Useful when you want the statements to execute at least once.

i.e reading input.


Do while example
do while example

do {

cout << “Enter a number between 1 and 10: “;

cin >> number;

} while (number <= 0 || number > 10);


Do while example1
do/while example

What will the output of the following program sequence be?

int j = 4;

do {

j = j - 2;

cout << “Hi”;

} while (++j > 0);

Walk through this example showing how j changes.


Loop exercises
Loop Exercises

1) How many times does the statement inside the do/while

body execute? What gets displayed?

int i = 0, x = 2;

do {

x = x + i;

} while (++ i < 3);

cout << “x = “ << x << endl;

2) How many times does the cout statement execute?

for (int i = 1; i <= 4; i++) {

for (int j = 1; j <= 3; j++) {

cout << “Hello” << endl;

}

}


Continue statement
continue statement

skip the rest of this iteration and continue with the next iteration of the loop

int x = 1;

while ( x <= 10) {

if (5 == x) {

x++;

continue;

}

cout << x << endl;

x++;

}

condition (x <= 10) is next statement executed after the continue statement.


Continue statement1
continue statement

  • for (int x = 1; x <= 10; x++) {

  • if (5 == x)

  • continue;

  • cout << x << endl;

  • }

  • next statements executed after continue are

  • x ++;

  • x <= 10;


Break statement
break statement

  • Breaks out of the loop. Next statement executed after a

  • break statement is the statement immediately following the loop.

    • for (int x = 1; x <= 10; x++) {

    • if (5 == x)

    • break;

    • cout << x << endl;

    • }

  • Next statement executed after the break statement is the

  • statement immediately following the for loop.


Else if example
else if example

if (‘A’ == lettergrade)

gpa = 4.0;

else if (‘B’ == lettergrade)

gpa = 3.0;

else if (‘C’ == lettergrade)

gpa = 2.0;

else if (‘D’ == lettergrade)

gpa = 1.0;

else if (‘F’ == lettergrade)

gpa = 0.0;

else

cout << “Illegal letter grade” << endl;


Switch statement
switch statement

switch (lettergrade) {

case ‘A’:

gpa = 4.0;

break;

case ‘B’:

gpa = 3.0;

break;

case ‘C’:

gpa = 2.0;

break;

case ‘D’:

gpa = 1.0;

break;

case ‘F’:

gpa = 1.0;

break;

default:

cout << “Illegal letter grade” << endl;

}


Switch statement syntax
switch statement syntax

switch (controlling expression) {

case label1: statement(s);

break;

case label2: statement(s);

break;

.

.

.

case labeln: statement(s);

break;

default: statement(s);

}


Switch statement rules
switch statement rules

  • controlling expression must be of type int or char

  • labels must be constants that match the type of the controlling expression

  • default statement can be anywhere. More intuitive at bottom.

  • can have multiple case labels sharing the same code

    case ‘A’: case ‘a’ :

    statements;

    break;


Else if that cannot be implemented as a switch
else if that cannot be implemented as a switch

int score;

cout << “Enter score: “;

cin >> score;

cout << “Your grade is “;

if (score < 68)

cout << “NR” << endl;

else if (score < 78)

cout << “C” << endl;

else if (score < 88)

cout << “B” << endl;

else

cout << “A” << endl;


Common programming errors
common programming errors

  • Forgetting the break statement. Statements for next case get executed by mistake.

  • Forgetting the space between the word case and the label. Will not be flagged by compiler but won’t execute the way you intend.


Grandma s attic
Grandma’s Attic

for (char letter = 'a'; letter <= ‘i'; letter++) {

cout << "I'm going to Grandma's attic and I'm going to get ";

switch (letter) {

case 'i': cout << "an igloo, ";

case 'h': cout << "a hat, ";

case 'g': cout << "a goat, ";

case 'f': cout << "a fox, ";

case 'e': cout << "an elephant, ";

case 'd': cout << "a dinosaur, ";

case 'c': cout << "a cookie, ";

case 'b': cout << "a ball and ";

case 'a': cout << "an apple" << endl;

default: break;

}

}


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