meljun cortes c++ chapter 2 c program controls structure

Introducing C’s Program Introducing C’s Program Control StatementsControl Statements

C Programming C Programming LanguageLanguage

MELJUN CORTESMELJUN CORTES

MELJUN CORTES, MBA,MPA,BSCSMELJUN CORTES, MBA,MPA,BSCS School of Computer InformationSchool of Computer Information 2

ObjectivesObjectives

CC’’s most important program control s most important program control

statements statements if, for if, for 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 Blocks of codeBlocks of code

The relational and logical operatorsThe relational and logical operators

More printf()More printf()


Ex. 1Ex. 1

Read two numbers to A and B. Read two numbers to A and B. Increase 1 number to A and decrease 1 number to Increase 1 number to A and decrease 1 number to

B.B.

STARTSTART

A = A + 1A = A + 1

B = B - 1B = B - 1

ENDEND

A, BA, B

READ A, BREAD A, B

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

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

int a, b; int a, b;

printf(“Input two numbers : ”); scanf(“%d%d”, &a, &b);

printf(“Input two numbers : ”); scanf(“%d%d”, &a, &b);

} }

a = a + 1; b = b - 1;

a = a + 1; b = b - 1;

printf(“A’s value : %d\n”, a); printf(“B’s value : %d\n”, b);

printf(“A’s value : %d\n”, a); printf(“B’s value : %d\n”, b);


Ex. 2Ex. 2

Read two numbers to A and B.Read two numbers to A and B. Swap A for B.Swap A for B.

AA BB

AA BB

temptemp


1.1. Become familiar with the Become familiar with the ifif

If statementsIf statements CC’’s selection statementss selection statements

Conditional statementsConditional statements

Logical dataLogical data truetrue

falsefalse

C doesnC doesn’’t have boolean datatype.t have boolean datatype. Use int, char datatype for logical dataUse int, char datatype for logical data

if(if(expressionexpression)) statement ;statement ;Execute when expression is true

The result is true or false


if (10>9) printf(“true”);if (10>9) printf(“true”);


Relational operatorRelational operator > : greater than> : greater than

expression

statement

true

false


if (9 < 5) printf(“this will not print”);if (9 < 5) printf(“this will not print”);


Relational operatorRelational operator < : less than< : less than



Example 1Example 1

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

int answer;

printf(“What is 10 + 14 ? ”);scanf(“%d”, &answer);

if(answer == 10+14) printf(“Right!”);

return 0;}


int answer;

printf(“What is 10 + 14 ? ”);scanf(“%d”, &answer);

if(answer == 10+14) printf(“Right!”);

return 0;}



Example 2 Example 2 (feet (feet –– meters conversion program) meters conversion program)



ExercisesExercises

Write a program that asks the user for an integer

and then tells the user if that number is even or odd.

(Hint, use C’s modulus operator %.)

Write a program that asks the user for an integer

and then tells the user if that number is even or odd.

(Hint, use C’s modulus operator %.)


Two-way Selection statementTwo-way Selection statement

2. Add the 2. Add the elseelse


ifif…… else logic flow else logic flow


;

;


Example 1Example 1



Example 2Example 2



ExercisesExercises


Write a program that requests two numbers and then

displays either their sum or product, depending on

what the user selects.

input two number : 28 5

select operator ( 1 : sum, 2 : product ) : 1

28 + 5 = 33


displays either their sum or product, depending on

what the user selects.


select operator ( 1 : sum, 2 : product ) : 1

28 + 5 = 33


ExercisesExercises



displays bigger number.


28 > 5


displays bigger number.


28 > 5


Code block : { the statements }Code block : { the statements }

3. Create blocks of code3. Create blocks of code

One logical unit

One logical unit


If the user enters any positive number, this If the user enters any positive number, this

fragment prints the messagefragment prints the message


scanf(“%d”, &num) ;

if(num > 0) {

printf(“This is ”) ;

printf(“an example of ”) ;

printf(“a code block.”) ;

}

scanf(“%d”, &num) ;

if(num > 0) {

printf(“This is ”) ;

printf(“an example of ”) ;

printf(“a code block.”) ;

}


Example 1Example 1



Example 2Example 2



ExercisesExercises


Write a program that either adds or subtracts two

integers. First, prompt the user to choose an operation;

then prompt for the two numbers and display the result.

select operator ( 1 : add, 2 : subtract ) : 1


28 + 5 = 33

Write a program that either adds or subtracts two

integers. First, prompt the user to choose an operation;

then prompt for the two numbers and display the result.

select operator ( 1 : add, 2 : subtract ) : 1


28 + 5 = 33


CC’’s loop statementss loop statements for loop / while loop / do.. while loopfor loop / while loop / do.. while loop

forfor loop allows one or more statements to be loop allows one or more statements to be repeated. repeated.

General form of General form of forfor loop loop

Initialization Initialization Conditional-testConditional-test incrementincrement

4. Use the 4. Use the forfor loop loop

for (initialization; conditional test; increment) statements;

for (initialization; conditional test; increment) statements;


Initialization Initialization Use to give an initial value to loop-control variableUse to give an initial value to loop-control variable Execute only once before the loop beginsExecute only once before the loop begins

Conditional-testConditional-test Is performed at the start of each iteration.Is performed at the start of each iteration. Test the loop-control variable against a target valueTest the loop-control variable against a target value True True the loop repeat the loop repeat False False the loop stop the loop stop

IncrementIncrement Is executed at the bottom of the loopIs executed at the bottom of the loop Increase or decrease the loop-control value by a certain Increase or decrease the loop-control value by a certain

amountamount




for statementfor statement



Simple exampleSimple example This program uses a for loop to print the This program uses a for loop to print the

numbers 1 through 10 on the screennumbers 1 through 10 on the screen

#include<stdio.h>

int main(void){

int num;

for(num=1; num<11; num=num+1)

printf(“%d ”, num) ;

printf(“terminating”);

return 0;

}

#include<stdio.h>

int main(void){

int num;




return 0;

} 1 2 3 4 5 6 7 8 9 10 terminating1 2 3 4 5 6 7 8 9 10 terminating



Example Example (loop will not execute)(loop will not execute)

#include<stdio.h>

int main(void){

int num;

//this loop will not execute




return 0;

}

#include<stdio.h>

int main(void){

int num;





return 0;

}terminatingterminating



Example Example (A for loop can run negatively)(A for loop can run negatively)

#include<stdio.h>

int main(void){

int num;


for(num=20; num>0; num=num-1)



return 0;

}

#include<stdio.h>

int main(void){

int num;


for(num=20; num>0; num=num-1)



return 0;

}20 19 18 17 …… 3 2 1 terminating20 19 18 17 …… 3 2 1 terminating



Using block to repeat several statementsUsing block to repeat several statements This program computes the product and sum of the This program computes the product and sum of the

numbers from 1 to 5.numbers from 1 to 5.

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

int num, sum, prod;sum = 0;prod = 1;for(num=1; num<6; num=num+1) {

sum = sum + num;prod = prod * num;

}printf(“product and sum : %d %d\n”, prod, sum) ;return 0;

}


int num, sum, prod;sum = 0;prod = 1;for(num=1; num<6; num=num+1) {

sum = sum + num;prod = prod * num;

}printf(“product and sum : %d %d\n”, prod, sum) ;return 0;

} product and sum : 120 15product and sum : 120 15



Example Example (increment or decrement by more than one)(increment or decrement by more than one) This program counts to 100 by fives.This program counts to 100 by fives.

#include<stdio.h>

int main(void){

int i;

for(i=0; i<101; i=i+5)

printf(“%d ”, i) ;

return 0;

}

#include<stdio.h>

int main(void){

int i;

for(i=0; i<101; i=i+5)

printf(“%d ”, i) ;

return 0;

}0 5 10 15 20 …… 90 95 1000 5 10 15 20 …… 90 95 100



Example 1. Example 1. (addition-drill)(addition-drill)



Example 2. Example 2. (determination of prime number)(determination of prime number)



Exercises 1.Exercises 1.

Create a program that prints the numbers from 1 to 100.

1 2 3 …… …… 8 9 10: : : :: : : :: : : :

91 92 93 …… …… 98 99 100

Create a program that prints the numbers from 1 to 100.

1 2 3 …… …… 8 9 10: : : :: : : :: : : :

91 92 93 …… …… 98 99 100




Write a program that prints the numbers between 17 to

100 that can be evenly divided by 17.

34 51 68 85

Write a program that prints the numbers between 17 to

100 that can be evenly divided by 17.

34 51 68 85




Write a program similar to the prime-number tester,

except that it displays all the factors of a number entered

By the user.

For example, if the user entered 8, it would respond with

2 and 4.

Enter a number : 8

8’s factor => 2 4

Write a program similar to the prime-number tester,

except that it displays all the factors of a number entered

By the user.

For example, if the user entered 8, it would respond with

2 and 4.

Enter a number : 8

8’s factor => 2 4


5. Substitute C5. Substitute C’’s increment and s increment and decrement Operatorsdecrement Operators

Increment operator (++)Increment operator (++) num = num +1; num = num +1; num++;num++;

Using for loopUsing for loop

Decrement operator (--)Decrement operator (--) count = count -1; count = count -1; count--;count--;

for(num=1; num<some_value; num=num+1) ……for(num=1; num<some_value; num=num+1) ……

for(num=1; num<some_value; num++) ……for(num=1; num<some_value; num++) ……



The Position of increment/decrement operatorThe Position of increment/decrement operator (++, (++, --)--) Although the effect on the variable is the same, the Although the effect on the variable is the same, the

position of the operator does affect when the operation is position of the operator does affect when the operation is performed.performed.


int i, j;i = 10;j = i++;// this will print 11 10printf(“i and j : %d %d\n”, i, j) ;return 0;

}


int i, j;i = 10;j = i++;// this will print 11 10printf(“i and j : %d %d\n”, i, j) ;return 0;

}



After the variable After the variable ( num++ )( num++ )

If max = 1 If max = 1 ResultResult

max = 2, count = 10max = 2, count = 10

First : the current value of variable is used for expression.First : the current value of variable is used for expression. After : increment expression execute.After : increment expression execute.

ArrangementArrangement

count = 10 * max++;count = 10 * max++;

count = 10 * max++;count = 10 * max++; count = 10 * max;

max = max + 1;

count = 10 * max;

max = max + 1;



Before the variable Before the variable ( ++num )( ++num ) First : increment expression execute.First : increment expression execute. After : the incremented value of variable is used for After : the incremented value of variable is used for

expression.expression.


int i, j;i = 10;j = ++i;// this will print 11 11printf(“i and j : %d %d\n”, i, j) ;return 0;

}


int i, j;i = 10;j = ++i;// this will print 11 11printf(“i and j : %d %d\n”, i, j) ;return 0;

}



Before the variable Before the variable ( num++ )( num++ )

If max = 1 If max = 1 ResultResult

max = 2, count = 20max = 2, count = 20

ArrangementArrangement

count = 10 * ++max;count = 10 * ++max;

count = 10 * ++max;count = 10 * ++max; max = max + 1;

count = 10 * max;

max = max + 1;

count = 10 * max;



Example 1.Example 1.




Change all appropriate assignment statements in this program to increment or decrement statements.


int a, b;a=1;a = a + 1;b = a;b = b – 1;printf(“%d %d”, a, b);return 0;

}

Change all appropriate assignment statements in this program to increment or decrement statements.


int a, b;a=1;a = a + 1;b = a;b = b – 1;printf(“%d %d”, a, b);return 0;

}




Enter a number. Compute summation until the number

from 1.

enter a number : 10

sum of 1 ~ 10 : 55

Enter a number. Compute summation until the number

from 1.

enter a number : 10

sum of 1 ~ 10 : 55




Enter a number. Compute factorial of the number.

enter a number : 3

3! = 6

enter a number : 5

5! = 120

enter a number : 10

10! = 3628800

Enter a number. Compute factorial of the number.

enter a number : 3

3! = 6

enter a number : 5

5! = 120

enter a number : 10

10! = 3628800


6. Expand 6. Expand printf()printf()’’s capabilitiess capabilities

Backslash codes Backslash codes Represent characters that cannot be entered from the Represent characters that cannot be entered from the

keyboard, and non-printing characterskeyboard, and non-printing characters

Escape characterEscape characterEscape characterEscape character



'\n' '\n' (newline character)(newline character) It translates it into a carriage return/linefeed It translates it into a carriage return/linefeed

combination.combination.

• backslash codes are character constants.

char ch; ch = '\t'; /* assign ch the tab character */

• backslash codes are character constants.

char ch; ch = '\t'; /* assign ch the tab character */


number square cube=============================== 1 1 1 2 4 8 3 9 27 : : : 10 100 1000

number square cube=============================== 1 1 1 2 4 8 3 9 27 : : : 10 100 1000


ExerciseExercise Using Using forfor loop (1~10) loop (1~10)


7. Program with C7. Program with C’’s relational s relational and Logical operatorsand Logical operators

Relational operatorsRelational operators Compare two values and return a true or false result Compare two values and return a true or false result

based upon that comparison.based upon that comparison.

Logical operatorsLogical operators Connect together true/false results.Connect together true/false results.



Truth table Truth table (AND, OR, NOT)(AND, OR, NOT)



Precedence of operatorsPrecedence of operators The relational and logical operators are both lower in The relational and logical operators are both lower in

precedence than the arithmetic operators.precedence than the arithmetic operators.

10 + count > a + 1210 + count > a + 12 (10 + count) > (a + 12)(10 + count) > (a + 12)

var > max || ! (max==100) && 0 <= itemvar > max || ! (max==100) && 0 <= item




if(count != 0) …… if(count != 0) …… if(count)if(count)

The expression !count is true only if count is zero.The expression !count is true only if count is zero.

if(count = = 0) …… if(count = = 0) …… if(!count)if(!count)



Example 2. Example 2. (the outcome of a relational or logical operation)(the outcome of a relational or logical operation)



Example 3. Example 3. (exclusive-OR)(exclusive-OR) XOR truth TableXOR truth Table

A function of XORA function of XOR



Example 3. Example 3. (exclusive-OR)(exclusive-OR) Demonstrate the xor()Demonstrate the xor()


Skills CheckSkills Check

Page 66 ~ 67Page 66 ~ 67

meljun cortes c++ chapter 2 c program controls structure

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