Chapter 5: Control Structures II (Repetition) C++ Programming 1 - - PowerPoint PPT Presentation

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Chapter 5: Control Structures II (Repetition)

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Objectives

Learn about repetition (looping) control structures Explore how to construct and use count-controlled, sentinel-controlled, flag-controlled, and EOF-controlled repetition structures Examine break and continue statements Discover how to form and use nested control structures Learn how to avoid bugs by avoiding patches Learn how to debug loops

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Why Is Repetition Needed?

• Repetition allows you to efficiently use variables
• Can input, add, and average multiple numbers

using a limited number of variables

• For example, to add five numbers:

–Declare a variable for each number, input the

numbers and add the variables together

–Create a loop that reads a number into a

variable and adds it to a variable that contains the sum of the numbers

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Read and Add Numbers

2 Numbers

int Sum; int N1; cin >> N1; int N2; cin >> N2; Sum = N1 + N2; cout << Sum;

INPUT N1 INPUT N2 COMPUTE Sum=N1+N2; OUPUT Sum START STOP

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Read and Add Numbers

3 Numbers

int Sum; int N1; cin >> N1; int N2; cin >> N2; int N3; cin >> N3; Sum = N1 + N2 + N3; cout << Sum;

INPUT N1 INPUT N2 COMPUTE Sum=N1+N2+N3; OUPUT Sum START STOP INPUT N3

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming N2

Read and Add Numbers

3 Numbers

int Sum; int N1; cin >> N1; int N2; cin >> N2; int N3; cin >> N3; Sum = N1 + N2 + N3; cout << Sum;

N1 N3

3 Numbers Sum so far

int Sum=0; int N1; cin >> N1; Sum = Sum + N1; int N2; cin >> N2; Sum = Sum + N2; int N3; cin >> N3; Sum = Sum + N3; cout << Sum;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming REPEAT 3 TIMES N2

Read and Add Numbers

N1 N3

int Sum=0; int N1; cin >> N1; Sum = Sum + N1; int N2; cin >> N2; Sum = Sum + N2; int N3; cin >> N3; Sum = Sum + N3; cout << Sum; int Sum=0; int N; cin >> N; Sum = Sum + N; cout << Sum;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

REPEAT 1000 TIMES

Read and Add Numbers

int Sum=0; int N; cin >> N; Sum = Sum + N; cout << Sum;

REPEAT 3 TIMES

int Sum=0; int N; cin >> N; Sum = Sum + N; cout << Sum;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

while Looping (Repetition) Structure

• The general form of the while statement is:

while is a reserved word

• Statement can be simple or compound
• Expression acts as a decision maker and is usually

a logical expression

• Statement is called the body of the loop
• The parentheses are part of the syntax

while ( Expression ) Statement;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

while Looping (Repetition) Structure

• Infinite loop: continues to execute endlessly

–Avoided by including statements in loop

body that assure exit condition is eventually

false

false true

Expression Statement while ( Expression ) Statement;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

while Looping (Repetition) Structure

i=0; while (i<=20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run: 0 5 10 15 20 i=25; while (i<=20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run:

5 times 0 times

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

while Looping (Repetition) Structure

i=0; while (i<=20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run: 0 5 10 15 20 i=0; while (i>=-20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run: _

5 times INFINITE

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

while Looping (Repetition) Structure

i=0; while (i<=20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run: 0 5 10 15 20 i=0; while (i<=20); { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run: _

5 times INFINITE times

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

while Looping (Repetition) Structure

i=0; while (i<=20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run: 0 5 10 15 20 i=0; while (i<20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run:

5 times

Random number

• r INFINITE

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

while Looping (Repetition) Structure

i=0; while (i<=20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run: 0 5 10 15 20 i=0; while (i<20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run: 0 0 0 0 0 0 0 0 0 ….

5 times

INFINITE

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Case 1: Counter-Controlled while Loops

• If you know exactly how many pieces of data need

to be read

//initialize the counter counter = 0; //test the counter while (counter < N) { //loop statements Statements; //update the counter counter++; }

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Counter-Controlled while Loops

counter = 0; while ( counter < N) { Statement; counter++; }

false true

counter < N Statement counter = 0 counter=counter +1

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

REPEAT 5 TIMES

Read and Add Numbers

int Sum=0; int counter=0; while (counter<5) { int N; cin >> N; Sum = Sum + N; counter++; } cout << Sum;

REPEAT 5 TIMES

int Sum=0; int N; cin >> N; Sum = Sum + N; cout << Sum;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Example: Sum of N Numbers

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Case 2: Sentinel-Controlled while Loops

• Sentinel variable is tested in the condition
• Loop ends when sentinel is encountered

//initialize the loop control variable cin >> variable; //test the loop control variable while (variable != SENTINEL) { //loop statements Statements; //update the loop control variable cin >> variable; }

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Sentinel-Controlled while Loops

false true

variable!= SENTINEL variable!= SENTINEL Statement

cin >> variable; while ( variable!= SENTINEL) { Statement; cin >> variable; }

INPUT variable INPUT variable

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Example: Sentinel-Controlled Sum

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Example: Letter to Telephone Digits

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Case 3: Flag-Controlled while Loops

A flag-controlled while loop uses a bool

variable to control the loop

//initialize the loop control variable found = false; //test the loop control variable while (!found) { //loop statements Statements; //update the loop control variable if (expression) found = true; }

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Flag-Controlled while Loops

found=false; while (!found) { Statement; if (expression) found=true; }

true false true

!found Statement found=false found=true expression

false

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

rand Function

Generate a random int value between 0 and

32767

In header file cstdlib To convert it to an integer greater than or equal to

0 and less than 100:

rand() % 100

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Example: Number Guessing Game

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Case 4: EOF-Controlled while Loops

Use an EOF (End Of File)-controlled while loop

to read from an input stream (file) as long as there is something in that stream

//initialize the loop control variable InputStream >> variable; //test the loop control variable while (InputStream) { //loop statements Statements; //update the loop control variable InputStream >> variable; }

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

EOF(End of File)-Controlled while Loops

cin >> variable; while (InputStream) { Statement; cin >> variable; }

false true

InputStream Statement INPUT variable INPUT variable

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

eof Function

The function eof can determine the end of file

status

Is true when you read beyond the end of the file

eof is a member of data type istream

The syntax for the function eof is:

where istreamVar is an input stream variable, such as cin or a input file variable

istreamVar.eof()

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Example: Grades

First Name Last Name TestScore Letter Grade

• …
• AVERAGE

LetterGrade= A if 90<TestScore B if 80<TestScore<90 C if 70<TestScore<80 D if 60<TestScore<70 F if TestScore<60

ClassAverage= ⋯ =

∑ "

• "#

For each student For the class

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Example: Grades

Flowchart

START INPUT FirstName, LastName, AverageTestScore

YES NO

InputFile STOP NumberStudents=0 INPUT FirstName, LastName, AverageTestScore Calculate LetterGrade Sum = Sum + TestScore NumberStudents = NumberStudents+1 ClassAverage = Sum/NumberStudents

OUTPUT Name + LetterGrade

Sum=0 OUTPUT ClassAverage

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Example: Grades

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

More on Expressions in while Statements

The expression in a while statement can be

complex

noOfGuesses=0; while ((noOfGuesses < 5) && (!isGuessed)) { cout << "Enter an integer greater than or equal to 0 and less than 100: "; cin >> guess; cout << endl; noOfGuesses++;

…

}

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Programming Example: Fibonacci Number

Consider the following sequence of numbers:

1, 1, 2, 3, 5, 8, 13, 21, 34, ....

Given the first two numbers of the sequence

(say, a1and a2)

nth number an, n >= 3, of this sequence is

given by: an = an-1 + an-2

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Programming Example: Fibonacci Number

Fibonacci sequence

nth Fibonacci number

a2 = 1 a1 = 1

Determine the nth number, an, n >= 3

a1 a2 a3 a4 a5

+

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Programming Example: Fibonacci Number

Input:

first two Fibonacci numbers the desired Fibonacci number n

Output:

nth Fibonacci number

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Programming Example: Fibonacci Number

Problem Analysis and Algorithm Design:

1.

Get the first two Fibonacci numbers

2.

Get the desired Fibonacci number

Get the position, n, of the Fibonacci number in the sequence

3.

Calculate the next Fibonacci number

By adding the previous two elements of the Fibonacci

sequence 4.

Repeat Step 3 until the nth Fibonacci number is found

5.

Output the nth Fibonacci number

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Variables

Programming Example: Fibonacci Number

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Programming Example: Fibonacci Number

• Main Algorithm:

1.

Prompt the user for the first two numbers—that is,

previous1 and previous2 2.

Read (input) the first two numbers into previous1 and previous2

3.

Output the first two Fibonacci numbers

4.

Prompt the user for the position of the desired Fibonacci number

5.

Read the position of the desired Fibonacci number into nthFibonacci

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Programming Example: Fibonacci Number

• a. if (nthFibonacci == 1)

The desired Fibonacci number is the first Fibonacci number. Copy the value of previous1 into current

• b. else if (nthFibonacci == 2)

The desired Fibonacci number is the second Fibonacci number. Copy the value of previous2 into current.

• c. else calculate the desired Fibonacci number as

follows:

• Initialize counter to 3 to keep track of the calculated

Fibonacci numbers. 6.

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Programming Example: Fibonacci Number

• Calculate the next Fibonacci number, as follows:

current = previous2 + previous1;

• Assign the value of previous2 to previous1
• Assign the value of current to previous2
• Increment counter
• Repeat until Fibonacci number is calculated
• 7. Output the nth Fibonacci number, which is current

previous2 previous1 current

+

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Programming Example: Fibonacci Number

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Programming Example: Fibonacci Number

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

• The general form of the for statement is:
• The InitialStatement, LoopCondition, and

UpdateStatement are called for loop control

statements

– InitialStatement usually initializes a variable

(called the for loop control, or for indexed, variable)

• In C++, for is a reserved word

for( InitialStatement; LoopCondition; UpdateStatement ) Statement;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

false true LoopCondition

Statement InitialStatement UpdateStatement

for( InitialStatement; LoopCondition; UpdateStatement ) Statement;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

for (i=0; i<10; i++) cout << i << “ ”; cout << endl;

Sample output:

0 1 2 3 4 5 6 7 8 9

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

for loop while loop

for (i=0; i<10; i++) cout << i << “ ”; cout << endl; i=0; while (i<10) {

cout << i << “ ”; i++;

} cout << endl;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

for(i=0; i<10; i++) cout << “Hello”; cout << “*”; for(i=0; i<10; i++) { cout << “Hello”; cout << “*”; }

simple statement compound statement

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

for(i=0; i<10; i++) { cout << “Hello”; cout << “ * ”; } for(i=0; i<10; i++); { cout << “Hello”; cout << “ * ”; }

10 times 1 time

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

• The following is a legal for loop:
• The following is a legal while loop:

for (;;) cout << "Hello\n”; while (1) cout << "Hello\n”;

• Both loops are legal, but not semantically correct.
• They are infinite loops (never end).

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

• C++ allows you to use fractional values for loop control

variables of the double type

– Results may differ. Avoid using them.

• An semicolon before the body of the loop will terminate

it.

for (i=0;i<5;i++); cout << “*" << endl;

• If the initial statement, loop condition, or

update statement are omitted (empty) they are

assumed to be true and the loop is an infinite loop.

for (;;) cout << “*" << endl;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

Not necessarily in increasing order – you can

decrement the loop control variable

for (i=10; i>0; i--) cout << i << “ ”; cout << endl;

Sample output:

10 9 8 7 6 5 4 3 2 1 for (i=10; i>=1; i--) cout << i << “ ”; cout << endl;

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

for Looping (Repetition) Structure

Not necessarily consecutive values for the loop control

variable

for (i=1; i<=10; i=i+2) cout << i << “ ”; cout << endl;

Sample output:

1 3 5 7 9 for (i=2; i<=10; i=i+2) cout << i << “ ”; cout << endl;

Sample output:

2 4 6 8 10

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Example: Fibonacci Number

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

do…while Looping (Repetition) Structure

• General form of a do...while:
• The statement executes first, and then the

expression is evaluated

• To avoid an infinite loop, body must contain a

statement that makes the expression false

• The statement can be simple or compound
• Loop always iterates at least once

do Statement; while ( Expression );

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

do…while Looping (Repetition) Structure

false true

Expression Statement do Statement; while ( Expression );

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

while Looping (Repetition) Structure

i=0; do { cout << i << “ ”; i=i+5; } while (i<=20); cout << “\n”; Sample run: 0 5 10 15 20 i=25; do { cout << i << “ ”; i=i+5; } while (i<=20); cout << “\n”; Sample run:

5 times 1 times

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

while Looping (Repetition) Structure

i=25; do { cout << i << “ ”; i=i+5; } while (i<=20); cout << “\n”; Sample run: i=25; while (i<=20) { cout << i << “ ”; i=i+5; } cout << “\n”; Sample run:

1 times 0 times

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Choosing the Right Looping Structure

All three loops have their place in C++

– If you know or can determine in advance the

number of repetitions needed, the for loop is the correct choice

– If you do not know and cannot determine in

advance the number of repetitions needed, and it could be zero, use a while loop

– If you do not know and cannot determine in

advance the number of repetitions needed, and it is at least one, use a do...while loop

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

break and continue Statements

• break and continue alter the flow of control
• break statement is used for two purposes:

–To exit early from a loop

• Can eliminate the use of certain (flag) variables

–To skip the remainder of the switch structure

• After the break statement executes, the

program continues with the first statement after the structure

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

break and continue Statements

continue is used in while, for, and

do…while structures

When executed in a loop

It skips remaining statements and proceeds

with the next iteration of the loop

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

break and continue Statements

break continue

for (i=0; i<10; i++) { if (i==5) break; cout << “ “ << i; } for (i=0; i<10; i++) { if (i==5) continue; cout << “ “ << i; } 0 1 2 3 4 0 1 2 3 4 6 7 8 9

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Nested Control Structures

Print N stars

for (j = 1; j <= N; j++) cout << "*";

Print the numbers from 1 to 5, one per line

for (i = 1; i <= 5 ; i++) { cout << i; cout << endl; }

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Nested Control Structures

Create and print the following pattern:

* ** *** **** *****

Code:

for (i = 1; i <= 5 ; i++) { for (j = 1; j <= i; j++) cout << "*"; cout << endl; }

On line i – print i stars

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Nested Control Structures

Create and print the following pattern:

***** **** *** ** *

Code:

for (i = 5; i >= 1; i--) { for (j = 1; j <= i; j++) cout << "*"; cout << endl; }

On line 5-i-1 – print i stars / decreasing order

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Nested Control Structures

Create and print the following pattern:

* ** *** **** *****

Code:

for (i = 1; i <= 5 ; i++) { for (j = 1; j <= 5-i; j++) cout << “ "; for (j = 1; j <= i; j++) cout << "*"; cout << endl; }

On line i – print 5-i spaces and i stars

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Nested Control Structures

Pattern:

* ** *** **** ***** **** *** ** *

Code:

for (i = 1; i <= 5 ; i++) { for (j = 1; j <= i; j++) cout << "*"; cout << endl; } for (i = 4; i >= 1; i--) { for (j = 1; j <= i; j++) cout << "*"; cout << endl; }

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Avoiding Bugs by Avoiding Patches

Software patch

Piece of code written on top of an existing

piece of code

Intended to fix a bug in the original code

Some programmers address the symptom of

the problem by adding a software patch

Should instead resolve underlying issue

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Debugging Loops

Loops are harder to debug than sequence and

selection structures

Use loop invariant

Set of statements that remains true each

time the loop body is executed

Most common error associated with loops is

• ff-by-one

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Summary

C++ has three looping (repetition) structures:

• while, for, and do…while

while and for loops are called pretest loops do...while loop is called a posttest loop while and for may not execute at all, but do...while always executes at least once

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• Dr. Adriana Badulescu Kallas

Introduction to Computer Science & Programming Programming Fundamentals I C++ Programming

Summary

while: expression is the decision maker, and the statement is the body of the loop A while loop can be:

• Counter-controlled
• Sentinel-controlled
• Flag-controlled
• EOF-controlled

for loop: simplifies the writing of a counter-controlled while loop Executing a break statement in the body of a loop immediately terminates the loop Executing a continue statement in the body of a loop skips to the next iteration