MELJUN CORTES C++ Chap3 Control Statements

8/10/2019 MELJUN CORTES C++ Chap3 Control Statements

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More C Program Control

Statements

C Programming Language


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MELJUN CORTES MBA MPA BSCS

School of Computer I nformation 2

Objectives

Cs most important program controlstatements while, do~while

Determine your programs flow of execution.

Form the backbone of your programs.

Well learn

Nested loops

More of control statements break, continueOther selection statement switch

Unconditional jump statement goto


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1. Input Characters

Using Library Functionsgetchar() : returns a single character typed on

the keyboard.

waits for a key to be pressed. (line buffers input)

waits until you enter a carriage return.

getche(): returns a single character immediately

after a key is pressed.

Interactive input


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1. Input Characters

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

}

getchar() function

getche() function#include #include

void main(void) {char ch;printf(Enter a character : );ch = getche(); /* read a char */printf(\nIts ASCII code is %d, ch);

}


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1. Input Characters

Example


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1. Input Characters

Exercises

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.)


7/68MELJUN CORTES MBA MPA BSCS


1. Input Characters

Exercises

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 if

if(error) printf(Error, try again.") ; // nested if

2. Nest if statements

When anifstatement is the target of another ifor elsenested if

using indent of a nested if increase readability

allow nested ifs at least 15 levels deep.

Indent




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

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


One confusing aspect of nested if

Dangling else

An elsealways associates with the nearestifin the same block that does not already have

anelseassociated with it.




if ( i != 0)

if ( i > 0 )

printf(positive!\n);

else

printf(necative!\n);

T

F

T


Dangling else - Example





F T

T

Dangling else solution





Examples

if (expression)

statement ;

else if (expression)

statement ;else if (expression)

statement ;

.

.

else

statement ;

if (expression) statement ;

else

if (expression) statement ;else

if (expression) statement ;

.

.

else statement ;


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Examples





Exercises

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


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#include

#include

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 variations

Flexibility of for loop

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


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#include

int main(void) {

int i;

printf("Enter an integer: ");

scanf("%d", &i);

for( ; i; i--)

printf("%d ", i); /* i times excute */return 0;

}


Examples expression empty


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#include

#include

int main(void) {

char ch;

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

printf(\nfound the q\n");

return 0;

}


Examples target empty


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for( ; ; ) {

}


Examples infinite loop


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#include

int main(void) {

int i;

for(i=0; i


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Exercises

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 30

Driving time : 1.67

Enter the distance and average speed : 100 80

Driving time : 1.25

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


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Exercises

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 dont display

anything on the screen.

============ Time-Delay program =========

Enter a number : 1000000

Good bye~~!!


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Exercises

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


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4. Understand Cs whileLoop

General form of whileloop

while (expression)

statement;


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Compound statements of whileloop


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#include

#include

int main(void) {

char ch;

ch=getche();

while(ch!='q)

ch=getche() ;

printf("found the q");

return 0;

}

Examples while loop


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#include

#include

int main(void) {

char ch;

printf(Enter your message. \n);

ch=getche();

while(ch!=\r) {

printf(%c, ch+1);

ch=getche() ;

}

return 0;

}

Examples simple code machine


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Exercises

Exercise 1 of Section 3.3 use a whileloop

============ Driving time computation program =========

How many compute driving time : 2Enter the distance and average speed : 50 30

Driving time : 1.67

Enter the distance and average speed : 100 80

Driving time : 1.25

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


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Exercises

Write a program that converts centigrade to fahrenheit. Use a

while 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

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


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5. Use the doLoop

General form of do_whileloop

do {

statements

} while (expression) ;


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5. Use the doLoop

Compound statements of doloop


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5. Use the doLoop

Examples reprompt the user until a valid input


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5. Use the doLoop

#include

#include

int main(void) {

char ch;

do {

ch=getche();

} while(ch!='q);

printf(Found the q. ");

return 0;

}

Examples do loop


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5. Use the doLoop

Exercises

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 : 1000

1000 gallons is 3785.4000 liters.

: :

Formula : L = 3.7854 * G ;

h d


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5. Use the doLoop

Exercises

Menu display

============ Mailing list menu =========

1. Enter address2. 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 C d L


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6. Create nested Loops

When the body of one loop contains another

for(i=0; i


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Example 1


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6 C d L


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Exercises

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 ..........

Prime number checking of a number(num)

for(i=2; i


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Exercises

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 output

65 periods.

============ Periods Printing Program ============A : ..

D : ..: :

: :N :

6 C t t d L


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Exercises star line

Write a program that prints star lines when given the

number of star.

============ Stars Printing Program ============

How many lines do you want to print : 5

6 C t t d L


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Exercises star line


number of star.



6 C t t d L


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Exercises star line


number of star.



6 C t t d L


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Exercises star line


number of star.



6 C t t d L


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Exercises star line


number of star.



6 Cr t t d L


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Exercises star line


number of star.



6 Create nested Loops


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Exercises star line


number of star.



7 Use break to exit a loop


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7. Use breakto exit a loop

allows you to exit a loop

for(i=1; i


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Using break in inner loops



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Example 1



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Example 2 exit from only the innermost loop

#include

int main(void) {

int i, j ;

for(i=0; i


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Exercises tip amount

Write a program that prints a table showing the proper amount

of tip to leave. Start the table at $1 and stop at $100, using

increments of $1. Compute three tip percentages : 10%, 15%, and

20%. 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) ? n

Thank you ~~!!

8 The continue statement


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8. The continuestatement

Forces the next iteration of the loop to take place,

skipping any code in between itself and the test

condition of loop.

#include

int main(void) {int x;

for(x=0; x


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Using continue in loops



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Example 1



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Exercises Using 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


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9. The switchstatement

Multiple selection statement.

The logic of switch statement

9 The switch statement


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The general form of the switch statement

Flow



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Demonstrate the switch statement


#include

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 */



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Results of the demonstration




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A switch with break statements




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Demonstrate the switch statement


#include

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;

}



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Switch will work with only intor chartypes.

It is possible to have a switch as part of the

statement sequence 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:

:



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Example 1


9. The switch statement


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Example 2




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Example 3


#include

#include

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;

}



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Exercises

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MELJUN CORTES C++ Chap3 Control Statements