additional control structures
DESCRIPTION
Additional Control Structures. Chapter 9 Topics. Switch Statement for Multi-way Branching Do-While Statement for Looping For Statement for Looping Using break and continue Statements To be able to choose the most appropriate looping statement for a given problem. Switch Statement. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/1.jpg)
1
Additional Control Structures
![Page 2: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/2.jpg)
2
Chapter 9 Topics Switch Statement for Multi-way Branching Do-While Statement for Looping For Statement for Looping Using break and continue Statements To be able to choose the most appropriate
looping statement for a given problem
![Page 3: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/3.jpg)
3
Switch Statement
Is a selection control structure for multi-way branching.SYNTAX
switch ( IntegralExpression ){
case Constant1 :Statement 1; // optional
case Constant2 :Statement 2; // optional
. . .
default : // optionalStatement n; // optional
}
![Page 4: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/4.jpg)
4
float weightInPounds = 165.8 ;char weightUnit ;
. . . // user enters letter for desired weightUnitswitch ( weightUnit ){
case ‘P’ :case ‘p’ :
cout << weightInPounds << “ pounds “ << endl ;break ;
case ‘O’ :case ‘o’ :
cout << 16.0 * weightInPounds << “ ounces “ << endl ;break ;
case ‘K’ :case ‘k’ :
cout << weightInPounds / 2.2 << “ kilos “ << endl ;break ;
case ‘G’ :case ‘g’ :
cout << 454.0 * weightInPounds << “ grams “ << endl ;break ;
default :cout << “That unit is not handled! “ << endl ;break ;
}
![Page 5: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/5.jpg)
5
Switch Statement
the value of IntegralExpression (of char, short, int, long or enum type ) determines which branch is executed
case labels are constant ( possibly named ) integral expressions. Several case labels can precede a same statement
![Page 6: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/6.jpg)
6
Switch(letter)
{case ‘X’ : Statement1;
break;
case ‘L’ :
case ‘M’: Statement2;
break;
case ‘S’ : Statement3;
break;
default : Statement4;
}
Statement5;
![Page 7: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/7.jpg)
7
In this example, letter is the switch expression.
The statement means
If letter is ‘X’,execute Statement1 and continue with Statement5.If letter is ‘L’ or ‘M’, execute Statement2 and continue with Statement5.If letter is ‘S’, execute Statement3 and continue with Statement5.If letter is none of the characters mentioned, execute Statement4 and continue with Statement5.
The Break statement causes an immediate exit from the Switch statement.
![Page 8: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/8.jpg)
8
Control in Switch Statement control branches to the statement following the case
label that matches the value of IntegralExpression. Control proceeds through all remaining statements, including the default, unless redirected with break
if no case label matches the value of IntegralExpression, control branches to the default label(if present)——otherwise control passes to the statement following the entire switch statement
forgetting to use break can cause logical errors
![Page 9: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/9.jpg)
9
Switch (grade) // Wrong Version
{
case ‘A’ :
case ‘B’ : cout <<“Good Work”;
case ‘C’ : cout <<“Average Work”;
case ‘D’ :
case ‘F’: cout <<“Poor Work”;
numberInTrouble++;
default : cout << grade <<“is not a valid letter grade.”
}
![Page 10: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/10.jpg)
10
If grade is ‘A’, the resulting output is this:
Good WorkAverage WorkPoor WorkA is not a valid letter grade.
Remember:
After a branch is taken to a specific case label, control proceeds sequentially until either a Break statement or the end of the Switch statement occurs.
![Page 11: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/11.jpg)
11
Do-While StatementIs a looping control structure in which the loop
condition is tested at the end(bottom) of the loop.
SYNTAX
do{
Statement
} while ( Expression ) ;
Loop body statement can be a single statement or a block.Note that the Do-While statement ends with a semicolon.
![Page 12: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/12.jpg)
12
void GetYesOrNo ( /* out */ char& response )
// Inputs a character from the user
// Postcondition: response has been input // && response == ‘y’ or ‘n’
{do{
cin >> response ; // skips leading whilespace
if ( ( response != ‘y’ ) && ( response != ‘n’ ) ) cout << “Please type y or n : ”;
} while ( ( response != ‘y’ ) && ( response != ‘n’ ) ) ;}
Function Using Do-While
![Page 13: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/13.jpg)
13
Do-While Loop vs. While Loop POST-TEST loop
(exit-condition) The looping condition
is tested after executing the loop body.
Loop body is always executed at least once.
PRE-TEST loop (entry-condition)
The looping condition is tested before executing the loop body.
Loop body may not be executed at all.
![Page 14: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/14.jpg)
14
Example
While Solution
sum=0;
counter=1;
while(counter<=n)
{
sum=sum+counter;
counter++;
}
Do-While Solution
sum=0;
counter=1;
do
{
sum=sum+counter;
counter++;
} while(counter<=n);
![Page 15: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/15.jpg)
15
If n is a positive number, both of these versions
are equivalent.
But if n is 0 or negative, the two loops give
different results.In the While version, the final value of sum is 0 because the
loop body is never entered.
In the Do-While version, the final value of sum is 1 because
the body executes once and then the loop test is made.
Example (Cont.)
![Page 16: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/16.jpg)
16
Do-While Loop
When the expression is tested and found to be false, the loop is exited and control passes to the statement that follows the do-while statement.
Statement
Expression
DO
WHILE
FALSE
TRUE
![Page 17: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/17.jpg)
17
A Count-Controlled Loop
SYNTAX
for ( initialization ; test expression ; update ) {
0 or more statements to repeat
}
![Page 18: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/18.jpg)
18
The for loop contains
an initialization
an expression to test for continuing
an update to execute after each
iteration of the body
![Page 19: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/19.jpg)
19
Example of Repetition
int num;
for ( num = 1 ; num <= 3 ; num++ )
{
cout << num << “Potato” << endl;
}
![Page 20: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/20.jpg)
20
Example of Repetition num
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
OUTPUT
?
![Page 21: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/21.jpg)
21
Example of Repetition num
OUTPUT
1
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
![Page 22: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/22.jpg)
22
Example of Repetition num
OUTPUT
1
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
true
![Page 23: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/23.jpg)
23
Example of Repetition num
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
OUTPUT
1
1Potato
![Page 24: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/24.jpg)
24
Example of Repetition num
OUTPUT
2
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
1Potato
![Page 25: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/25.jpg)
25
Example of Repetition num
OUTPUT
2
true
1Potato
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
![Page 26: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/26.jpg)
26
Example of Repetition num
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
OUTPUT
2
1Potato
2Potato
![Page 27: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/27.jpg)
27
Example of Repetition num
OUTPUT
3
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
1Potato
2Potato
![Page 28: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/28.jpg)
28
Example of Repetition num
OUTPUT
3
true
1Potato
2Potato
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
![Page 29: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/29.jpg)
29
Example of Repetition num
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
OUTPUT
3
1Potato
2Potato
3Potato
![Page 30: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/30.jpg)
30
Example of Repetition num
OUTPUT
4
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
1Potato
2Potato
3Potato
![Page 31: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/31.jpg)
31
Example of Repetition num
OUTPUT
4
false
1Potato
2Potato
3Potato
int num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
![Page 32: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/32.jpg)
32
Example of Repetition num
When the loop control condition is evaluated and has value false, the loop is said to be “satisfied” and control passes to the statement following the For statement.
4
falseint num;
for ( num = 1 ; num <= 3 ; num++ )
cout << num << “Potato” << endl;
![Page 33: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/33.jpg)
33
The output was:
1Potato2Potato3Potato
![Page 34: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/34.jpg)
34
int count ;
for ( count = 4 ; count > 0 ; count-- )
{
cout << count << endl;
}
cout << “Done” << endl;
Count-controlled Loop
OUTPUT: 4321Done
![Page 35: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/35.jpg)
35
What is output?
int count;
for ( count = 0 ; count < 10 ; count++ ){
cout << “”;}
![Page 36: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/36.jpg)
36
OUTPUT
**********
NOTE: the 10 asterisks are all on one line. Why?
![Page 37: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/37.jpg)
37
What output from this loop?
int count;
for (count = 0; count < 10; count++) ;
{
cout << “”;
}
![Page 38: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/38.jpg)
38
no output from the for loop! Why? the ; right after the ( ) means that the body
statement is a null statement in general, the Body of the for loop is whatever
statement immediately follows the ( ) that statement can be a single statement, a
block, or a null statement actually, the code outputs one * after the loop
completes its counting to 10
OUTPUT
![Page 39: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/39.jpg)
39
Several Statements in Body Block
const int MONTHS = 12 ;
int count ;
float bill ;
float sum = 0.0 ;
for (count = 1; count <= MONTHS; count++ )
{
cout << “Enter bill: ” ;
cin >> bill ;
sum = sum + bill ;
}
cout << “Your total bill is : ” << sum << endl ;
![Page 40: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/40.jpg)
40
Nested For Loops
For( lastNum=1; lastNum<=7; lastNum++)
{
for(numToPrint=1; numToPrint<=lastNum; numToPrint++)
cout << numToPrint;
cout << endl;
}
![Page 41: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/41.jpg)
41
Output
It prints the following triangle of numbers.
1
12
123
1234
12345
123456
1234567
![Page 42: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/42.jpg)
42
Break Statement
break statement can be used with Switch or any of the 3 looping structures
it causes an immediate exit from the Switch, While, Do-While, or For statement in which it appears
if the break is inside nested structures, control exits only the innermost structure containing it
![Page 43: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/43.jpg)
43
Continue Statement is valid only within loops
terminates the current loop iteration, but not the entire loop
in a For or While, continue causes the rest of the body statement to be skipped--in a For statement, the update is done
in a Do-While, the exit condition is tested, and if true, the next loop iteration is begun
![Page 44: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/44.jpg)
44
Be sure to note
the difference between continue and break.
The Continue statement means “Abandon the current
iteration of the loop, and go on to the next iteration.”
The Break statement means “Exit the entire loop
immediately.”
![Page 45: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/45.jpg)
45
Guidelines for Choosing a Looping Statement
If the loop is a simple count-controlled loop, the For statement
is natural.
If the loop is an event-controlled loop whose body should
execute at least once, a Do-While statement is appropriate.
If the loop is an event-controlled loop and nothing is
known about the first execution, use a While statement.
When in doubt, use a While statement.
Using Break statement and Continue statement only after
careful consideration.
![Page 46: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/46.jpg)
46
Imagine using . . .
a character, a length, and a width to draw a box, for example,
using the values ‘&’, 4, and 6 would display
&&&&&&
&&&&&&
&&&&&&
&&&&&&
![Page 47: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/47.jpg)
47
Write prototype for void function
called DrawBox ( ) with 3 parameters. The first is type char, the other 2 are type int.
void DrawBox( char, int , int );
NOTE: Some C++ books include identifiers in prototypes. Any valid C++ identifiers, as long as each is different, can be used.
void DrawBox( char letter, int num1, int num2);
![Page 48: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/48.jpg)
48
void DrawBox(char what, int down, int across) // 3 function parameters
{
int row, col; // 2 local variables
for ( row = 0; row < down; row++ )
{
for (col = 0; col < across; col++ )
{
cout << what;
}
cout << endl;
}
return;
}
![Page 49: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/49.jpg)
49
#include <iostream>
void DrawBox (char, int, int); // prototype
int main ( ) {
char letter = ‘&’;
DrawBox(letter, 4, 2*3); // arguments DrawBox(‘V’, 9, 3); // appear in call
return 0;}
THE DRIVER PROGRAM
![Page 50: Additional Control Structures](https://reader036.vdocuments.us/reader036/viewer/2022062422/5681324f550346895d98c95c/html5/thumbnails/50.jpg)
50
Write a function using prototype
void DisplayTable ( int ) ; // prototype
The function displays a specified multiplication table. For example, the call DisplayTable(6) displays this table:
1 x 6 = 6 2 x 6 = 12 3 x 6 = 18
.
.
.
12 x 6 = 72