selection statement 01204111 – selection statement modified from aj. thanachat thanomkulabut’s...
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Selection Statement
01204111 – Selection Statement
Modified from Aj. Thanachat Thanomkulabut’s slide
1st semester, 2012
Outline2
Boolean expression Flowchart if statement if…else… statement nested if statement switch case statement
Boolean expression
Operators Comparison
Equal == Not equal != Less < Greater > Less than or equal to <= Greater than or equal to >=
Boolean And && Or || Not !
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Boolean Expression
0 and 0 = 00 and 1 = 01 and 0 = 01 and 1 = 1
0 or 0 = 00 or 1 = 11 or 0 = 11 or 1 = 1
not 0 = 1not 1 = 0
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Boolean expression
int Y; Y
Is Y greater than 3? Y>3
Is Y less than 5? Y<5
Is Y between 3 and 5? (Y<5)(Y>3)&&
Boolean Expression
Boolean Expression Example
From the equation: X2+9X+10 = 0 How can we check that value of X is the
answer for above equation?
Condition: Is Y an even number?
((X*X +9*X +10) == 0) //true if X is the answer
(Y%2 == 0) //true if Y is even
OR
(Y%2 != 1) //true if Y is even
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Boolean Expression
Example: Boolean Expressions
double x = 4.0; Expression Value
x < 5.0 ___________x > 5.0 ___________x <= 5.0 ___________5.0 == x ___________x != 5.0 ___________(3!=4)&&(7<5) ___________(4>4)||(5<=10) ___________
truefalsetruefalsetrue
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Boolean Expression
falsetrue
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Boolean variable
Used for storing Boolean value true false
Keyword: bool Usage example: int X = 0;
bool MyVar = true; //Boolean variable declaration
MyVar = (X>0); //Boolean expression
Boolean variable
Outline8
Boolean expression Flowchart if statement if…else… statement
Flowchart symbols overview
Graphical representation
Terminator
Process
Input/output
Condition
Connector
Flow line
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Flowchart
Program flowchart example
Start
Statement1
Statement2
Statement3
Statement4
End
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Flowchart
Outline11
Boolean expression Flowchart if statement if…else… statement
if statement
Execute the specific statement when the ”condition” becomes true
Syntax:
if (condition)
statement;
if (condition) {
statement1;
statement2;
}if (condition) {
statement;
}
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if statement
true
true
if statement13
conditionFalse
True
Statement
if (condition)
statement;
if (condition) {
statement;
}
if statement
if statement14
condition
FalseTrue
Statement1
Statement2
if (condition) {
statement1;
statement2;
}
if statement
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if statement with Boolean variable
bool Y;int X = int.Parse(Console.ReadLine());Y = (X > 10);
if (Y) console.Write(“X is greater than 10”);else console.Write(“X is less than or equal to 10”);
if statement
if statement
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if statement example BMI (Body Mass Index)
BMI Weight Status
Below 18.5 Underweight
18.5 – 24.9 Normal
25.0 – 29.9 Overweight
30.0 and Above Obese (Extremely Fat)
BMI =Weight in Kilograms
(Height in Meters) X (Height in Meters)
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if statement
BMI Weight Status
Below 18.5 Underweight
18.5 – 24.9 Normal
25.0 – 29.9 Overweight
30.0 and Above Obese (Extremely Fat)
BMI =Weight in Kilograms
(Height in Meters) X (Height in Meters)
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double BMI = W /(H*H);
if(BMI<18.5) Console.WriteLine(“Underweight”);
if(BMI>=18.5 && BMI<=24.9) Console.WriteLine(“Normal”);
if(BMI>=25.0 && BMI<=29.9) Console.WriteLine(“Overweight”);
if statement example
if(BMI>=30.0) Console.WriteLine(“Obese”);
Outline19
Boolean expression Flowchart if statement if…else… statement
if…else… statement flowchartstatement1;
if (condition) {
statement2; //true
}
else {
statement3; //false
}
statement4;
Start
Statement1
Condition
Statement2 Statement3
true false
Statement4
End
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Flowchart
if…else… statement
If condition is true execute statement1 If condition is false execute statement2 Syntax:if (condition)
statement1; //true
else
statement2; //false
if (condition)
statement1; //true
else {
statement2; //false
statement3; //false
}
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if…else… statement
if…else… statement22
conditionFalseTrue
Statement2Statement1
if (condition)
statement1; //true
else
statement2; //false
if…else… statement
if…else… statement23
if (condition)
statement1; //true
else {
statement2; //false
statement3; //false
}
conditionFalseTrue
Statement2
Statement1
Statement3
if…else… statement
if… else… statement flowchart
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n= int.Parse(Console.ReadLine());
if (n>0)
n= 2*n+5;
else {
Console.Write(“Go”);
n = n%4;
}
Start
n>0
n=2*n+5;
true false
n=n%4;
End
n=int.Parse(Console.ReadLine());
Console.Write(“Go”);
Flowchart
if…else… statement example
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Write a program that checks if the input number is odd or even. input : integer number output : message to inform that number is
odd or even.
Value in N Output
Even Number It’s even number.
Odd Number It’s odd number.
if…else… statement
if…else… statement example
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Value of n OutputEven Number It’s even number.
Odd Number It’s odd number.
if(n%2 == 0)
Console.WriteLine(“It’s even number”);else
Console.WriteLine(“It’s odd number”);
if…else… statement
Test I27
Write a program that computes the value of a f(x) based on the value of x input : number x output : f(x)
f(x) x
x2+1 x<0
x+2 x≥0
if…else… statement
Summary28
Boolean expression Flowchart if statement if…else… statement nested if statement switch case statement
Any question?