Decision Making And Branching 4t233n

Decision Making and branching C Decision Making Home 1

Conitional Statements – If Statement | If-Else

2

Nesting of Statements – Nested If-Else | Else-If Ladder

3

Multiple Condition inside If

4

Multiple Statements in If Block

4

Introduction to Switch Statement

5

Rules of Using Switch Case

6

Invalid Ways of Using Switch Case

7

Conditional Operation : ?: Operator | Rules

8

Jumping Statements : Goto Statement | Break

Syntax : if(expression) statement1; Explanation :  

Expression is Boolean Expression It may have true or false value

Meaning of If Statement :  

It Checks whether the given Expression is Boolean or not !! If Expression is True Then it executes the statement otherwise jumps to next_instruction

Sample Program Code : void main() { int a=5,b=6,c; c=a+b;

if (c==11) printf("Execute me 1"); printf("Execute me 2"); } Output : Execute me 1 If Statement : if(conditional) { Statement No 1 Statement No 2 Statement No 3 . . . Statement No N } Note : 1. More than One Conditions can be Written inside If statement. 2. Opening and Closing Braces are required only when “Code” after if statement occupies multiple lines. if(conditional) Statement No 1; Statement No 2; Statement No 3; In the above example only Statement 1 is a part of if Statement. 1. Code will be executed if condition statement is True. 2. Non-Zero Number Inside if means “TRUE Condition” if(100) printf("True Condition"); Program flow of If Statement :

If-else Statement in C Programming

We can use if-else statement in c programming so that we can check any condition and depending on the outcome of the condition we can follow appropriate path. We have true path as well as false path. Syntax : if(expression) { statement1; statement2; } else { statement1; statement2; } next_statement; Explanation :  

If expression is True then Statement1 and Statement2 are executed Otherwise Statement3 and Statement4 are executed.

Sample Program on if-else Statement : void main() { int marks=50; if(marks>=40) { printf("Student is "); } else { printf("Student is Fail"); } }Output : Student is Flowchart : If Else Statement

Consider Example 1 with Explanation :

Consider Following Example int num = 20; if(num == 20) { printf("True Block"); } else { printf("False Block"); } If part Executed if Condition Statement is True. if(num == 20) { printf("True Block"); } True Block will be executed if condition is True. Else Part executed if Condition Statement is False. else { printf("False Block"); } Consider Example 2 with Explanation : More than One Conditions can be Written inside If statement. int num1 = 20; int num2 = 40; if(num1 == 20 && num2 == 40) { printf("True Block"); } Opening and Closing Braces are required only when “Code” after if statement occupies multiple lines. Code will be executed if condition statement is True. Non-Zero Number Inside if means “TRUE Condition” If-Else Statement : if(conditional) { //True code } else { //False code }

Note :

Consider Following Example int num = 20; if(num == 20) { printf("True Block"); } else { printf("False Block"); } 1. If part Executed if Condition Statement is True. if(num == 20) { printf("True Block"); } True Block will be executed if condition is True. 2. Else Part executed if Condition Statement is False. else { printf("False Block"); } 3. More than One Conditions can be Written inside If statement. int num1 = 20; int num2 = 40; if(num1 == 20 && num2 == 40) { printf("True Block"); } 4. Opening and Closing Braces are required only when “Code” after if statement occupies multiple lines. 5. Code will be executed if condition statement is True. 6. Non-Zero Number Inside if means “TRUE Condition”

Program Flow of If-Else Statement :

Compound If Statement in C Programming : void main ( ) { int num = 10 ; if(num > 0) { printf ("\nNumber is Positive"); printf ("\nThis is The Example of Compound Statement"); } } Output of Program : Number is Positive This is The Example of Compound Statement Explanation of Compound If Statement : In C Programming, Any block of the code is written or embedded inside the pair of the curly braces. If condition specified inside the „if block‟ is true then code block written inside the pair of curly braces will be executed. printf ("\nNumber is Positive"); printf ("\nThis is The Example of Compound Statement"); Note : We can write any number of statements inside block if condition is true Single Statement after „if‟ Does not Require Opening and Closing Braces : Tutorial on If

1. Single Statement after if Does not Require Opening And Closing Braces 2. Example : void main ( ) { int x = 10 ; if ( x > 0 ) printf (“n Number is Positive”); }

Expression Solving inside if Statement : C programming Arithmetic expression can be solved inside if statement. In this case expression will be evaluated first and then result will be checked to decide the flow of code. void main () { int num = 56; if(num % 2 == 0) // Expression printf ("\nNumber is Even"); else printf ("\nNumber is Odd"); } Explanation of Statement : Consider the if statement – if(num % 2 == 0) above if statement contain simple expression which will be evaluated like this Result of Expression = (num % 2 == 0) = (56 % 2 == 0) = (0 == 0) Now we can say that result of above expression is true thus if statement condition becomes true and if block gets executed. Expression Solving : Arithmetic Operation We will consider different verities of statements , Please refer below table -

if(60)

Expression Result True

if(0)

True

Zero Number inside if will make condition false and else block gets executed

if(-60)

True

Negative number will be considered as true and if block gets executed

If Statement

Comment Positive Number inside if will execute if block

if(20 - 20 + Expression will be executed and then it will be checked True 50) whether it is non-zero or zero Non Zero Number is considered as true and Zero will be considered as false C switch case statement Why we should use Switch Case ? 1. One of the classic problem encountered in nested if-else / else-if ladder is called problem of Confusion. 2. It occurs when no matching else is available for if . 3. As the number of alternatives increases the Complexity of program increases drastically. 4. To overcome this , C Provide a multi-way decision statement called „Switch Statement„

See how difficult is this scenario ? if(Condition 1) Statement 1 else { Statement 2 if(condition 2) { if(condition 3) statement 3 else if(condition 4) { statement 4 } } else { statement 5 } } First Look of Switch Case switch(expression) { case value1 : body1 break; case value2 :

body2 break;

case value3 :

body3 break;

default :

default-body break;

} next-statement; Flow Diagram :

*Steps are Shown in Circles.

How it works ? 

  

Switch case checks the value of expression/variable against the list of case values and when the match is found , the block of statement associated with that case is executed Expression should be Integer Expression / Character Break statement takes control out of the case. Break Statement is Optional.

01:#include<stdio.h> 02:void main() 03:{ 04:int roll = 3 ; 05:switch ( roll ) 06: { 07: case 1: 08: printf ( " I am Pankaj "); 09: break; 10: case 2: 11: printf ( " I am Nikhil "); 12: break; 13: case 3: 14: printf ( " I am John "); 15: break; 16: default : 17: printf ( "No student found"); 18: break; 19: } 20:} As explained earlier 1. 3 is assigned to integer variable „roll„ 2. On line 5 switch case decides – “We have to execute block of code specified in 3rd case“. 3. Switch Case executes code from top to bottom. 4. It will now enter into first Case [i.e case 1:] 5. It will validate Case number with variable Roll. If no match found then it will jump to Next Case.. 6. When it finds matching case it will execute block of code specified in that case. See how Switch Case works using Graphical Picture

Rules of Using Switch Case in C Programming

1. Case Label must be unique 2. Case Labels must ends with Colon 3. Case labels must have constants / constant expression 4. Case label must be of integral Type ( Integer,Character) 5. Case label should not be „floating point number „ 6. Switch case should have at most one default label 7. Default label is Optional 8. Default can be placed anywhere in the switch 9. Break Statement takes control out of the switch 10. Two or more cases may share one break statement 11. Nesting ( switch within switch ) is allowed. 12. Relational Operators are not allowed in Switch Statement. 13. Macro Identifier are allowed as Switch Case Label. 14. Const Variable is allowed in switch Case Statement. 15. Empty Switch case is allowed. Syntax of Switch Case : switch ( expression ) { case label1 : body1 break; case label2 : body2 break; case label3 : body3 break; default : default-body break; } next-statement;

Rule 1 : Case Label must be unique int id = 3 ; switch(id) { case 1: case 2: case 2: default :

printf("C Programming Language"); break; printf("C++ Programming Language"); break; printf("Web Technology"); break; printf("No student found"); break;

}

Rule 2 : Case Labels must ends with Colon

case 1 : printf("C Programming Language"); break; Rule 3 : Case labels must have constants / constant expression case 1+1: case 'A': case 67: these are allowed examples of switch case labels , however variables are not allowed in switch case labels. case var : case num1 : case n1+n2 : Rule 4 : Case label must be of integral Type ( Integer,Character) whereas Case label should not be „floating point number „ case 10: case 20+20: case 'A': case 'a': these are allowed examples and following are illegal examples case 10.12: case 7.5: Rule 5 : Switch case should have at most one default label switch(roll) { case 1: printf("C Programming Language"); break; case 2: printf("C++ Programming Language"); break; case 2: printf("Web Technology"); break; default : printf("Default Version 1"); break; default : printf("Default Version 2"); break; } It violets first rule. Rule 6 : Default label is Optional switch(roll) { case 1 : printf("C Programming Language");

break; case 2 : printf("C++ Programming Language"); break; case 2 : printf("Web Technology"); break; } default statement is optional. It can be neglected. Rule 7 : Default can be placed anywhere in the switch switch(roll) { case 1 : printf("C Programming Language"); break; default: printf("No Student Found"); break; case 2 : printf("C++ Programming Language"); break; case 2 : printf("Web Technology"); break; } Rule 8 : Break Statement takes control out of the switch Rule 9 : Two or more cases may share one break statement switch(alpha) { case 'a': case 'A': printf("Alphabet A"); break; case 'b': case 'B': printf("Alphabet B"); break; } Rule 10 : Nesting ( switch within switch ) is allowed switch(alpha) { case 'a': case 'A': printf("Alphabet A"); break; case 'b': case 'B': switch(alpha) { }

break; } nesting of switch case is allowed in C. Rule 11 : Relational Operators are not allowed in Switch Statement. switch(num) { case >15: printf("Number > 15"); break; case =15: printf("Number = 15"); break; case <15: printf("Number < 15"); break; } relational operators are not allowed as switch label. Rule 12 : Macro Identifier are allowed as Switch Case Label. #define MAX 2 switch(num) { case MAX: printf("Number = 2"); break; } as preprocessor will replace occurrence of MAX by constant value i.e 2 therefor it is allowed. Rule 13 : Const Variable is allowed in switch Case Statement. int const var = 2; switch(num) { case var: printf("Number = 2"); break; }

Conditional Operators [ ?: ] : Ternary Operator Statement in C 1. They are also called as Ternary Operator . 2. They also called as ?: operator 3. Ternary Operators takes on 3 Arguments Syntax : expression 1 ? expression 2 : expression 3 where

  

expression1 is Condition expression2 is Statement Followed if Condition is True expression2 is Statement Followed if Condition is False

Conditional Statement in C Programming Lanuage Meaning of Syntax : 1. Expression1 is nothing but Boolean Condition i.e it results into either TRUE or FALSE 2. If result of expression1 is TRUE then expression2 is Executed 3. Expression1 is said to be TRUE if its result is NON-ZERO 4. If result of expression1 is FALSE then expression3 is Executed 5. Expression1 is said to be FALSE if its result is ZERO Example : Check whether Number is Odd or Even #include<stdio.h> int main() { int num; printf("Enter the Number : "); scanf("%d",&num); flag = ((num%2==0)?1:0); if(flag==0) printf("\nEven"); else printf("\nOdd"); } More Simply we can write this program as #include<stdio.h>

int main() { int num; printf("Enter the Number : "); scanf("%d",&num); (num%2==0)?printf("Even"):printf("Odd"); } Big Note : Ternary Operator Operator that works on 3 operands is called as tertiary operator. Ternary operator .

Goto Statement goto label; ------------label :

Whenever goto keyword encountered then it causes the program to continue on the line , so long as it is in the scope . Types of Goto :  

Note :

Forward Backward

#include <stdio.h> int main () { /* local variable definition */ int a = 10; /* do loop execution */ LABEL10:do { if( a == 15) { /* skip the iteration */ a = a + 1; goto LABEL10; } printf("value of a: %d\n", a); a++; }while( a < 20 ); return 0; } output value of value of value of value of value of value of value of value of value of

a: a: a: a: a: a: a: a: a:

10 11 12 13 14 16 17 18 19

Break Statement Simply Terminate Loop and takes control out of the loop. Break in For Loop : for(initialization ; condition ; incrementation) { Statement1;

Statement2; break; }

Break in While Loop : initialization ; while(condition) { Statement1; Statement2; incrementation break; }

Break Statement in Do-While : initialization ; do { Statement1; Statement2; incrementation break; }while(condition);

Way 1 : Do-While Loop

Way 2 : Nested for

Way 3 : For Loop

Way 4 : While Loop