meljun cortes c++ chapter 3 control statements

More C Program Control More C Program Control StatementsStatements

C Programming C Programming LanguageLanguage

MELJUN CORTESMELJUN CORTES

MELJUN CORTES, MELJUN CORTES, MBA,MPA,BSCSMBA,MPA,BSCS

School of Computer InformationSchool of Computer Information 2

ObjectivesObjectives

CC’’s most important program control statements s most important program control statements while, do~while while, do~while Determine your programDetermine your program’’s flow of execution.s flow of execution. Form the backbone of your programs.Form the backbone of your programs.

WeWe’’ll learnll learn Nested loopsNested loops More of control statements More of control statements break, continuebreak, continue Other selection statement Other selection statement switchswitch Unconditional jump statement Unconditional jump statement gotogoto



1.1. Input CharactersInput Characters

Using Library FunctionsUsing Library Functions getchar() getchar() : returns a single character typed on the : returns a single character typed on the

keyboard. keyboard. <stdio.h><stdio.h> waits for a key to be pressed. waits for a key to be pressed. (line buffers input)(line buffers input) waits until you enter a carriage return.waits until you enter a carriage return.

getche()getche() : returns a single character immediately after : returns a single character immediately after a key is pressed. a key is pressed. <conio.h><conio.h> Interactive inputInteractive input




#include <stdio.h>void main(void) { char ch; ch = getchar(); /* read a char */ printf(" you typed: %c", ch);}

#include <stdio.h>void main(void) { char ch; ch = getchar(); /* read a char */ printf(" you typed: %c", ch);}

getchar() functiongetchar() function

getche() functiongetche() function#include <stdio.h>#include <conio.h>void main(void) { char ch; printf(“Enter a character : “); ch = getche(); /* read a char */ printf(“\nIts ASCII code is %d”, ch);}

#include <stdio.h>#include <conio.h>void main(void) { char ch; printf(“Enter a character : “); ch = getche(); /* read a char */ printf(“\nIts ASCII code is %d”, ch);}




ExampleExample




ExercisesExercises

Write a program that reads ten letters, After the

Letters have been read, display the one that comes

earliest in the alphabet.

(Hint, The one with the smallest value comes first.)

Write a program that reads ten letters, After the

Letters have been read, display the one that comes

earliest in the alphabet.

(Hint, The one with the smallest value comes first.)




ExercisesExercises

Write a program that displays the ASCII codes for the

characters A through Z. and a through z. How do the

codes differ between the upper- and lowercase

characters?

Write a program that displays the ASCII codes for the

characters A through Z. and a through z. How do the

codes differ between the upper- and lowercase

characters?



if (count > max) // outer ifif(error) printf(“Error, try again.") ; // nested if

if (count > max) // outer ifif(error) printf(“Error, try again.") ; // nested if

2. Nest if statements2. Nest if statements

When anWhen an if if statement is the target of another statement is the target of another ifif or or elseelse nested ifnested if

• using indent of a nested if increase readability

• allow nested ifs at least 15 levels deep.

• using indent of a nested if increase readability

• allow nested ifs at least 15 levels deep.

IndentIndent



if (p) if(q) printf(“a and b are true") ;

else printf(“To which statement does this else apply?”);

if (p) if(q) printf(“a and b are true") ;

else printf(“To which statement does this else apply?”);


One confusing aspect of nested ifOne confusing aspect of nested if

Dangling elseDangling else

An else always associates with the nearest ifin the same block that does not already have an else associated with it.

An else always associates with the nearest ifin the same block that does not already have an else associated with it.



if ( i != 0)

if ( i > 0 )

printf(“positive!\n”);

else

printf(“necative!\n”);

TF

F T


Dangling else - ExampleDangling else - Example




F T

TF

Dangling else solutionDangling else solution




ExamplesExamples

if (expression) statement ; else if (expression) statement ; else if (expression) statement ; . . else statement ;







ExamplesExamples




ExercisesExercises

Write a program that computes the area of either a circle, rectangle, or triangle.Use an if-else-if ladder.

Write a program that computes the area of either a circle, rectangle, or triangle.Use an if-else-if ladder.

============ Area computation program =========Choice shape ( 1 : circle, 2 : rectangle, 3 : triangle ) : 1Input radius : 10Area of the circle is 31.40

Choice shape ( 1 : circle, 2 : rectangle, 3 : triangle ) : 2Input width : 10Input height : 20Area of the rectangle is 200.00

============ Area computation program =========Choice shape ( 1 : circle, 2 : rectangle, 3 : triangle ) : 1Input radius : 10Area of the circle is 31.40

Choice shape ( 1 : circle, 2 : rectangle, 3 : triangle ) : 2Input width : 10Input height : 20Area of the rectangle is 200.00



#include <stdio.h>#include <conio.h> int main(void){

int i;char ch;ch = 'a'; /* give ch an initial value */

for(i=0; ch!='q'; i++) { /* if ch is ‘q‘, stop loop */ printf("pass: %d\n", i); ch = getche();} return 0;

}

#include <stdio.h>#include <conio.h> int main(void){

int i;char ch;ch = 'a'; /* give ch an initial value */

for(i=0; ch!='q'; i++) { /* if ch is ‘q‘, stop loop */ printf("pass: %d\n", i); ch = getche();} return 0;

}

3. Examine for loop variations3. Examine for loop variations

Flexibility of for loop Flexibility of for loop one or more of the expressions inside for may be empty.one or more of the expressions inside for may be empty.



#include <stdio.h> int main(void) {

int i;printf("Enter an integer: ");scanf("%d", &i);

for( ; i; i--) printf("%d ", i); /* i times excute */

return 0; }

#include <stdio.h> int main(void) {

int i;printf("Enter an integer: ");scanf("%d", &i);

for( ; i; i--) printf("%d ", i); /* i times excute */

return 0; }


Examples Examples –– expression empty expression empty



#include <stdio.h>

#include <conio.h>

int main(void) {

char ch;

for(ch=getche(); ch!='q'; ch=getche()) ;

printf(“\nfound the q\n");

return 0;

}

#include <stdio.h>

#include <conio.h>

int main(void) {

char ch;

for(ch=getche(); ch!='q'; ch=getche()) ;

printf(“\nfound the q\n");

return 0;

}


Examples Examples –– target emptytarget empty



for( ; ; ) {

……

}

for( ; ; ) {

……

}


Examples Examples –– infinite loopinfinite loop



#include <stdio.h>

int main(void) {

int i;

for(i=0; i<10; ) {

printf("%d ", i);

i++;

}

return 0;

}

#include <stdio.h>

int main(void) {

int i;

for(i=0; i<10; ) {

printf("%d ", i);

i++;

}

return 0;

}


Examples Examples –– outside the increment sectionoutside the increment section




ExercisesExercises

Write a program that computes driving time when given the distance and the average speed.Let the user specify the number of drive time computations he or she wants to perform.

Write a program that computes driving time when given the distance and the average speed.Let the user specify the number of drive time computations he or she wants to perform.

============ Driving time computation program =========How many compute driving time : 2Enter the distance and average speed : 50 30Driving time : 1.67Enter the distance and average speed : 100 80Driving time : 1.25


▶ Formula : dist = speed * time time = dist / speed▶ Formula : dist = speed * time time = dist / speed




ExercisesExercises

To create time-delay loops, for loops with empty targets are

often used. Create a program that asks the user for a number

and then iterates until zero is reached.

Once the countdown is done, sound the bell, but don’t display

anything on the screen.

To create time-delay loops, for loops with empty targets are

often used. Create a program that asks the user for a number

and then iterates until zero is reached.

Once the countdown is done, sound the bell, but don’t display

anything on the screen.

============ Time-Delay program =========Enter a number : 1000000Good bye~~!!

============ Time-Delay program =========Enter a number : 1000000Good bye~~!!




ExercisesExercises

Write a program that begins at 1 and runs to 1000.

Have the program add the loop-control variable to itself inside

the increment expression.

This is an easy way to produce the arithmetic progression 1 2 4

8 16, and so on.

Write a program that begins at 1 and runs to 1000.

Have the program add the loop-control variable to itself inside

the increment expression.

This is an easy way to produce the arithmetic progression 1 2 4

8 16, and so on.

1 2 4 8 16 32 ……1 2 4 8 16 32 ……



4. Understand C4. Understand C’’s s whilewhile Loop Loop

General form of General form of whilewhile loop loop

while (expression) statement;

while (expression) statement;

;




Compound statements of Compound statements of whilewhile loop loop




#include <stdio.h>

#include <conio.h>

int main(void) {

char ch;

ch=getche();

while(ch!='q‘)

ch=getche() ;

printf("found the q");

return 0;

}

#include <stdio.h>

#include <conio.h>

int main(void) {

char ch;

ch=getche();

while(ch!='q‘)

ch=getche() ;

printf("found the q");

return 0;

}

Examples Examples –– while loopwhile loop




#include <stdio.h>#include <conio.h> int main(void) {

char ch;printf(“Enter your message. \n”);ch=getche();while(ch!=‘\r‘) {

printf(“%c”, ch+1);ch=getche() ;

}return 0;

}

#include <stdio.h>#include <conio.h> int main(void) {

char ch;printf(“Enter your message. \n”);ch=getche();while(ch!=‘\r‘) {

printf(“%c”, ch+1);ch=getche() ;

}return 0;

}

Examples Examples –– simple code machinesimple code machine




ExercisesExercises

Exercise 1 of Section 3.3 use a while loopExercise 1 of Section 3.3 use a while loop



▶ Formula : dist = speed * time time = dist / speed▶ Formula : dist = speed * time time = dist / speed




ExercisesExercises

Write a program that converts centigrade to fahrenheit. Use awhile loop and compute from 5 to 50 of centigrade. Increasing value is 5.

Centigrade Fahrenheit

Write a program that converts centigrade to fahrenheit. Use awhile loop and compute from 5 to 50 of centigrade. Increasing value is 5.

Centigrade Fahrenheit

============ Fahrenheit computation program ========= 5 Centigrade is 41.00 Fahrenheit10 Centigrade is 50.00 Fahrenheit 15 Centigrade is 59.00 Fahrenheit : :50 Centigrade is 122.00 Fahrenheit

============ Fahrenheit computation program ========= 5 Centigrade is 41.00 Fahrenheit10 Centigrade is 50.00 Fahrenheit 15 Centigrade is 59.00 Fahrenheit : :50 Centigrade is 122.00 Fahrenheit

▶ Formula : F = 9/5 * C + 32 ;▶ Formula : F = 9/5 * C + 32 ;



5. Use the 5. Use the dodo Loop Loop

General form of General form of do_whiledo_while loop loop

do {statements

} while (expression) ;

do {statements

} while (expression) ;




Compound statements of Compound statements of dodo loop loop




Examples Examples –– reprompt the user until a valid inputreprompt the user until a valid input




#include <stdio.h>

#include <conio.h>

int main(void) {

char ch;

do {

ch=getche();

} while(ch!='q‘);

printf(“Found the q. ");

return 0;

}

#include <stdio.h>

#include <conio.h>

int main(void) {

char ch;

do {

ch=getche();

} while(ch!='q‘);

printf(“Found the q. ");

return 0;

}

Examples Examples –– do loopdo loop




ExercisesExercises

Write a program that converts gallons to liters. Using a do loop,allow the user to repeat the conversion.

Gallon Liter

Write a program that converts gallons to liters. Using a do loop,allow the user to repeat the conversion.

Gallon Liter

============ Gallons to Liters program =========Enter the Gallons : 100100 gallons is 378.5400 liters. Enter the Gallons : 10001000 gallons is 3785.4000 liters.: :

============ Gallons to Liters program =========Enter the Gallons : 100100 gallons is 378.5400 liters. Enter the Gallons : 10001000 gallons is 3785.4000 liters.: :

▶ Formula : L = 3.7854 * G ;▶ Formula : L = 3.7854 * G ;




ExercisesExercises

Menu displayMenu display

============ Mailing list menu ========= 1. Enter address 2. Delete address 3. Search the list 4. Print the list 5. Quit Enter the number of your choice (1-5) : 3

Search the list

Good Bye~~!!

============ Mailing list menu ========= 1. Enter address 2. Delete address 3. Search the list 4. Print the list 5. Quit Enter the number of your choice (1-5) : 3

Search the list

Good Bye~~!!



6. Create nested Loops6. Create nested Loops

When the body of one loop contains anotherWhen the body of one loop contains another

for(i=0; i<10; i++) {for(j=1; j<11; j++) printf(“%d ”, j); // nested loopprintf(“\n”);

}

for(i=0; i<10; i++) {for(j=1; j<11; j++) printf(“%d ”, j); // nested loopprintf(“\n”);

}

1 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 10




Example 1Example 1




Example 2Example 2




ExercisesExercises

Write a program that finds all the prime numbers between 2 and 1000.Write a program that finds all the prime numbers between 2 and 1000.

============ The Prime Numbers ============The Prime Numbers : 2 3 5 7 11 13 17 19 ..........============ The Prime Numbers ============The Prime Numbers : 2 3 5 7 11 13 17 19 ..........

▶ Prime number checking of a number(num) for(i=2; i<num; i++)for(i=2; i<num; i++)

if(num % i==0) if(num % i==0) prime_number = 0 ;prime_number = 0 ;

▶ Prime number checking of a number(num) for(i=2; i<num; i++)for(i=2; i<num; i++)

if(num % i==0) if(num % i==0) prime_number = 0 ;prime_number = 0 ;




ExercisesExercises

Write a program that reads ten characters from the keyboard.Each time a character is read, use its ASCII code value to output a string of periods equal in number to this code. For example, given the letter ‘A’, whose code is 65, your program would output65 periods.

Write a program that reads ten characters from the keyboard.Each time a character is read, use its ASCII code value to output a string of periods equal in number to this code. For example, given the letter ‘A’, whose code is 65, your program would output65 periods.

============ Periods Printing Program ============A : ………………………………………………………..D : …………………………………………………………..: :: :N : ……………………………………………………………………

============ Periods Printing Program ============A : ………………………………………………………..D : …………………………………………………………..: :: :N : ……………………………………………………………………




Exercises Exercises –– star linestar line

Write a program that prints star lines when given thenumber of star.Write a program that prints star lines when given thenumber of star.

============ Stars Printing Program ============How many lines do you want to print : 5★★★★★★★★★★★★★★★★★★★★★★★★★

============ Stars Printing Program ============How many lines do you want to print : 5★★★★★★★★★★★★★★★★★★★★★★★★★






============ Stars Printing Program ============How many lines do you want to print : 5★★★★★★★★★★★★★★★







============ Stars Printing Program ============How many lines do you want to print : 5 ★ ★★ ★★★ ★★★★★★★★★

============ Stars Printing Program ============How many lines do you want to print : 5 ★ ★★ ★★★ ★★★★★★★★★






============ Stars Printing Program ============How many lines do you want to print : 5★★★★★ ★★★★ ★★★ ★★ ★

============ Stars Printing Program ============How many lines do you want to print : 5★★★★★ ★★★★ ★★★ ★★ ★






============ Stars Printing Program ============How many lines do you want to print : 5 ★ ★★★ ★★★★★ ★★★★★★★★★★★★★★★★

============ Stars Printing Program ============How many lines do you want to print : 5 ★ ★★★ ★★★★★ ★★★★★★★★★★★★★★★★






============ Stars Printing Program ============How many lines do you want to print : 5★★★★★★★★★ ★★★★★★★ ★★★★★ ★★★ ★

============ Stars Printing Program ============How many lines do you want to print : 5★★★★★★★★★ ★★★★★★★ ★★★★★ ★★★ ★



7. Use 7. Use breakbreak to exit a loop to exit a loop

allows you to exit a loopallows you to exit a loop

for(i=1; i<100; i++) {printf(“%d ”, i); if(i==10) break;break; // exit the loop

}

for(i=1; i<100; i++) {printf(“%d ”, i); if(i==10) break;break; // exit the loop

}

1 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 10




Using break in inner loopsUsing break in inner loops




Example 1Example 1




Example 2 Example 2 –– exit from only the innermost loopexit from only the innermost loop

#include <stdio.h>int main(void) {

int i, j ; for(i=0; i<5; i++) {

for(j=0; j<=100; j++) {printf(“%d ”, j);if(j==5) break;

}printf(“\n”);

}return 0;

}

#include <stdio.h>int main(void) {

int i, j ; for(i=0; i<5; i++) {

for(j=0; j<=100; j++) {printf(“%d ”, j);if(j==5) break;

}printf(“\n”);

}return 0;

}




Exercises Exercises –– tip amounttip amount

Write a program that prints a table showing the proper amountof tip to leave. Start the table at $1 and stop at $100, using increments of $1. Compute three tip percentages : 10%, 15%, and20%. After each line, ask the user if he or she wants to continue.If not, use break to stop the loop and end the program.

Write a program that prints a table showing the proper amountof tip to leave. Start the table at $1 and stop at $100, using increments of $1. Compute three tip percentages : 10%, 15%, and20%. After each line, ask the user if he or she wants to continue.If not, use break to stop the loop and end the program.

============ Tip amount Program ============total Tip : 10% 15% 20%$1 0.10 0.15 0.20 continue (y/n) ? y$2 0.20 0.30 0.40 continue (y/n) ? y$3 0.30 0.45 0.60 continue (y/n) ? nThank you ~~!!

============ Tip amount Program ============total Tip : 10% 15% 20%$1 0.10 0.15 0.20 continue (y/n) ? y$2 0.20 0.30 0.40 continue (y/n) ? y$3 0.30 0.45 0.60 continue (y/n) ? nThank you ~~!!



8. The 8. The continuecontinue statement statement

Forces the next iteration of the loop to take place, Forces the next iteration of the loop to take place, skipping any code in between itself and the test condition skipping any code in between itself and the test condition of loop.of loop.

#include <stdio.h>int main(void) { int x; for(x=0; x<100; x++) { continue; printf("%d ", x); /* This is never executed. */ }

}

#include <stdio.h>int main(void) { int x; for(x=0; x<100; x++) { continue; printf("%d ", x); /* This is never executed. */ }

}




Using continue in loopsUsing continue in loops




Example 1Example 1




Exercises Exercises –– Using continueUsing continue

Write a program that prints only the odd numbers between 1

and 100. Use a for loop that looks like this :

for(i=1; i<101; i++) ……

Use a continue statement to avoid printing even numbers.

Write a program that prints only the odd numbers between 1

and 100. Use a for loop that looks like this :

for(i=1; i<101; i++) ……

Use a continue statement to avoid printing even numbers.

============ Odd Number Printing Program ============

1 3 5 7 9 11 13 15 17 19 …… 95 97 99

============ Odd Number Printing Program ============

1 3 5 7 9 11 13 15 17 19 …… 95 97 99



9. The 9. The switchswitch statement statement

Multiple selection statement.Multiple selection statement. The logic of switch statementThe logic of switch statement




The general form of the switch statementThe general form of the switch statement

FlowFlow



Demonstrate the switch statementDemonstrate the switch statement


#include <stdio.h>int main (void) { int printFlag; printf(“Please enter a integer:”); scanf(“%d”, &printFlag);

switch (printFlag) { case 1: printf(“This is case 1\n”); case 2: printf(“This is case 2\n”); default: printf(“This is default\n”); }} /* main */

#include <stdio.h>int main (void) { int printFlag; printf(“Please enter a integer:”); scanf(“%d”, &printFlag);

switch (printFlag) { case 1: printf(“This is case 1\n”); case 2: printf(“This is case 2\n”); default: printf(“This is default\n”); }} /* main */



Results of the demonstrationResults of the demonstration




A switch with break statementsA switch with break statements




Demonstrate the switch statementDemonstrate the switch statement


#include <stdio.h> int main(void) { int i; printf("Enter a number between 1 and 4: "); scanf("%d", &i);

switch(i) { case 1: printf("one");

break; case 2: printf("two");

break;

#include <stdio.h> int main(void) { int i; printf("Enter a number between 1 and 4: "); scanf("%d", &i);

switch(i) { case 1: printf("one");

break; case 2: printf("two");

break;

case 3: printf("three"); break; case 4: printf("four"); break; default: printf("unrecognized number"); } return 0; }

case 3: printf("three"); break; case 4: printf("four"); break; default: printf("unrecognized number"); } return 0; }



Switch will work with only Switch will work with only intint or or charchar types. types. It is possible to have a switch as part of the statement It is possible to have a switch as part of the statement

sequence of an outer switchsequence of an outer switch


switch(a) { case 1: switch(b) { case 0: printf("b is false"); break; case 1: printf("b is true"); } break; case 2: :

switch(a) { case 1: switch(b) { case 0: printf("b is false"); break; case 1: printf("b is true"); } break; case 2: :



Example 1Example 1




Example 2Example 2




Example 3Example 3


#include <stdio.h>#include <conio.h>int main(void) { char ch; printf("Enter the letter: "); ch = getche(); switch(ch) { case 'a': case 'e': case 'i': case 'o': case 'u': case 'y': printf(" is a vowel\n");

break; default: printf(" is a consonant"); }

return 0;}

#include <stdio.h>#include <conio.h>int main(void) { char ch; printf("Enter the letter: "); ch = getche(); switch(ch) { case 'a': case 'e': case 'i': case 'o': case 'u': case 'y': printf(" is a vowel\n");

break; default: printf(" is a consonant"); }

return 0;}




ExercisesExercises

meljun cortes c++ chapter 3 control statements

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char ch ch

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