Control structures determine the order of execution of statements in a program. There are three main types: sequential, selectional, and iterative. Selectional structures include if and switch statements. If statements allow for conditional execution of code based on boolean expressions. Switch statements select execution based on a variable's value and allow for multiple case blocks. Nested if statements involve if blocks within other if blocks.

1. Control Structures

3. The following approaches can be chosen depending on the problem statement:

4. Sequential

5. In a sequentialapproach, all the statements are executed in the same order as it is written

6. Selectional

7. In a selectional approach, based on some conditions, different set of statements are executed

8. Iterational (Repetition)

10. Simple if Statement In a simple ‘if’ statement, a condition is tested If the condition is true, a set of statements are executed If the condition is false, the statements are not executed and the program control goes to the next statement that immediately follows if block Syntax: if (condition) { Statement(s); } Next Statement; if (iDuration >= 3) { /* Interest for deposits equal to or more than 3 years is 6.0% */ fRateOfInterest = 6.0; }

12. The statement ‘else’ provides the sameSyntax: if (condition) { Statement set-1; } else { Statement set-2; } Next Statement;

15. When one condition is false, it checks for the next condition and so on

16. When all the conditions are false the ‘else’ block is executed

17. The statements in that conditional block are executed and the other ‘if’ statements are skipped Syntax: if (condition-1) { Statement set-1; } else if (condition-2) { Statement set-2; } ……………………………… else if (condition-n) { Statement set-n; } else { Statement set-x; }

19. Example (1 of 2 ) #include<stdio.h> #include<conio.h> main() { int result; printf("Enter your mark:"); scanf("%d",&result); if (result >=55) { printf("Passed"); printf("Congratulations"); } else { printf("Failed"); printf("Good luck repeating this subject :D "); } getch(); return 0; } 77 55 48 21

20. Example (2 of 2 ) #include<stdio.h> #include<conio.h> main() { int test1,test2; int result; printf("Enter your mark for Test 1:"); scanf("%d",&test1); printf("Enter your mark for Test 2:"); scanf("%d",&test2); result=(test1+test2)/2; if(result>=80) { printf("Passed: Grade A"); } else if (result>=70) { printf("Passed: Grade B"); } else if (result >=55) { printf("Passed: Grade C"); } else { printf("Failed"); } getch(); return 0; }

21. Assignment(=) vs. Equality Operator (==) (1 of 3) The operator ‘=’ is used for assignment purposes whereas the operator ‘==’ is used to check for equality It is a common mistake to use ‘=’ instead of ‘==’ to check for equality The compiler does not generate any error message Example: if (interest = 6.5) { printf(“Minimum Duration of deposit: 6 years”); } else if (interest = 6.0) { printf(“Minimum Duration of deposit: 3 years”); } else { printf(“No such interest rate is offered”); } The output of the above program will be “Minimum Duration of deposit: 6 years” the control structure Is ignored

26. Example: if (iDuration > 6 ) { if (dPrincipalAmount > 25000) { printf(“Your percentage of incentive is 4%”); } else { printf(“Your percentage of incentive is 2%”); } else { printf(“No incentive”); }

27. #include<stdio.h> #include<conio.h> main() { intiDuration, dPrincipalAmount; printf("Enter value for iDuration:"); scanf("%d",&iDuration); if (iDuration > 6 ) { printf("What is youtdPrincipalAmount:"); scanf("%d",&dPrincipalAmount); if (dPrincipalAmount > 25000) { printf("Your percentage of incentive is 4%"); } else { printf("Your percentage of incentive is 2%"); } } else { printf("No incentive"); } getch(); return 0; } What the output if iDuration=9 dPrincipalAmount=26000 iDuration=10 dPrincipalAmount=21000 iDuration=4 dPrincipalAmount=21000

28. Example Nested if What the output if num1=55 num2=55 num1=25 num2=89 num1=90 num2=10 #include<stdio.h> #include<conio.h> main() { int num1; int num2; printf("Please enter two integers"); printf("Num1:"); scanf("%d",&num1); printf("Num2:"); scanf("%d",&num2); if(num1<=num2) { if(num1<num2) { printf("%d < %d", num1,num2); } else { printf("%d==%d",num1,num2); } } else { printf("%d > %d",num1, num2); } getch(); return 0; }

29. What is the output of the following code snippet? iResult = iNum % 2; if ( iResult = 0) { printf("The number is even"); } else { printf("The number is odd"); } CASE 1: When iNum is 11 CASE 2: When iNum is 8 The output is "The number is odd" The output is "The number is odd" Explains???

31. It is very similar to ‘if’ statement

32. But ‘switch’ statement cannot replace ‘if’ statementin all situations Syntax: Switch(integer variable or integer expression or character variable) { case integer or character constant-1 : Statement(s); break; case integer or character constant-2 : Statement(s); break; …………… case integer or character constant-n : Statement(s); break; default: Statement(s); break; }

33. What is the output of the following code snippet? intiNino= 2; switch(iNino){ case 1: printf(“ONE”); break; case 2: printf(“TWO”); break; case 3: printf(“THREE”); break; default: printf(“INVALID”); break; } Output: TWO

35. What is the output of the following code snippet? unsigned int iCountOfItems = 5; switch (iCountOfItems) { case iCountOfItems >=10 : printf(“Enough Stock” ); break; default : printf(“Not enough stock”); break; } Error: Relational Expressions cannot be used in switch statement

36. An Example – switch case #include<stdio.h> #include<conio.h> main() { char ch; printf("Enter the vowel:"); scanf("%c",&ch); switch(ch) { case 'a' : printf("Vowel"); break; case 'e' : printf("Vowel"); break; case 'i' : printf("Vowel"); break; case 'o' : printf("Vowel"); break; case 'u' : printf ("Vowel"); break; default : printf("Not a vowel"); } getch(); return 0; }

37. An Example – switch case char ch=‘a’; switch(ch) { case ‘a’ : printf(“Vowel”); break; case ‘e’ : printf(“Vowel”); break; case ‘i’ : printf(“Vowel”); break; case ‘o’ : printf(“Vowel”); break; case ‘u’ : printf (“Vowel”); break; default : printf(“Not a vowel”); } char ch=‘a’; switch(ch) { case ‘a’ : case ‘e’ : case ‘i’ : case ‘o’ : case ‘u’ : printf(“Vowel”); break; default : printf(“Not a vowel”); }

38. An Example – switch case #include<stdio.h> #include<conio.h> main() { int greeting; printf("Enter the number of your desired greetings :"); scanf("%d",&greeting); switch (greeting){ case 1: printf("Happy Hari Raya"); break; case 2: printf("Happy Deepavali"); break; case 3: printf("Happy New Year"); break; default: printf("You choose wrong choice"); break; } getch(); return 0; } If you choose 1…Happy Hari Raya 2…Happy Deepavali 3… Happy New Year Other than that……. You choose wrong choice

40. The statements are executed as long as the condition is true

41. These kind of control structures are also called as loop control structures

42. are three kinds of loop control structures:

43. while

44. do while

46. do while Loop Control Structure Execution proceeds as follows: First the loop is executed, next the condition is evaluated, if condition evaluates to true the loop continues execution else control passes to the next statement following the loop The do-while statement can also terminate when a break, goto, or returnstatement is executed within the statement body. This is an example of the do-while statement: do{ a = b ; b = b – 1; } while ( b > 0 ); In the above do-while statement, the two statements a = b; and b = b - 1; are executed, regardless of the initial value of b. Then b > 0 is evaluated. If b is greater than 0, the statement body is executed again and b > 0 is reevaluated. The statement body is executed repeatedly as long as b remains greater than 0. Execution of the do-while statement terminates when b becomes 0 or –ve. The body of the loop is executed at least once.

47. do while Loop Control Structure Example int iNumber, iSum = 0; do { printf(“Enter a number. Type 0(zero) to end the input ”); scanf(“%d”,&iNumber); iSum = iSum + iNumber; } while (iNumber != 0);

48. Difference between while and do while loops

49. do – while and whileExample #include<stdio.h> #include<conio.h> int main(void) { int x=1; do{ printf("%d", x++); } while (x<5); getch(); return 0; } #include<stdio.h> #include<conio.h> int main(void) { int x=1; while(x<5){ printf("%d", x); x++; } getch(); return 0; } 2 3 4

50. for Loop Control Structure The ‘for’ loops are similar to the other loop control structures The ‘for’ loops are generally used when certain statements have to beexecuted a specific number of times Advantage of for loops: All the three parts of a loop (initialization, condition and increment) can be given in a single statement Because of this, there is no chance of user missing out initialization or increment steps which is the common programming error in ‘while’ and ‘do while’ loops Syntax: for (Initialization; Termination-Condition; Increment-Step) { Set of statement(s); } Next Statement;

51. Syntax: for (Initialization; Termination-Condition; Increment-Step) { Set of statement(s); } Next Statement; In executing a for statement, the computer does the following: Initializationis executed. Then the Termination-conditionis evaluated. If it computes to zero the loop is exited. If the (1)Termination-conditiongives a nonzero value, the (2)LoopBody is executed and then the (3)Increment-stepis evaluated. The Termination-condition is again tested. Thus, the LoopBody is repeated until the Termination-condition computes to a zero value.

52. for Loop Control Structure Example: int iCount; for (iCount = 1; iCount <= 10; iCount++) { printf(“%d”,iCount); } 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

53. for Loop Control Structure /* Check for n number of students, whether they have passed or not */ #include<stdio.h> #include<conio.h> int main(void) { intiCounter, iNoOfStudents; float fMark1, fMark2, fMark3, fAvg, fSum; for(iCounter=1; iCounter<=iNoOfStudents; iCounter++) { /* Accepting the marks scored by the students in 3 subjects */ /* Display a message before accepting the marks*/ printf("Enter the marks scored by the student %d in 3 subjects", iCounter); printf("Subject1:"); scanf("%f",&fMark1); printf("Subject2:"); scanf("%f",&fMark2); printf("Subject3:"); scanf("%f",&fMark3); /* calculating the average marks */ fSum=fMark1+fMark2+fMark3; fAvg=fSum/3; /* compare the average with 65 and decide whether student has passed or failed */ if ( fAvg >= 65.0) printf("Student %d - PASSES", iCounter); else printf("Student %d - FAILS", iCounter); } getch(); return 0;}

54. for Loop Control Structure #include<stdio.h> #include<conio.h> int main(void) { int x, y; for(x=0,y=1;x<y;x++) printf("%d %d",x,y); getch(); return 0; } O 1

55. for Loop Control Structure #include<stdio.h> #include<conio.h> int main(void) { int x; for(x=1;x<5;x++) printf("%d",x); getch(); return 0; } 1 2 3 4

56. What is the output of the following code snippet? int iNum; int iCounter; int iProduct; for(iCounter=1; iCounter<= 3; iCounter++) { iProduct = iProduct * iCounter; } printf("%d", iProduct); The output is a junk value -- WHY??? This is because iProduct is not initialized

57. What is the output of the following code snippet? for(iCount=0;iCount<10;iCount++); { printf("%d",iCount); } The output is 10 int iCount; for(iCount=0;iCount<10;iCount++) { printf("%d",iCount); } The output is 0 1 2 3 4 5 6 7 8 9

58. for and while loops Rewrite it using while statement #include<stdio.h> #include<conio.h> int main(void) { intiSum,iCtr,iNum; iSum=0,iCtr=0; while(iCtr<10){ printf("Enter mark: "); scanf("%d",&iNum); iSum=iSum+iNum; iCtr=iCtr+1; } printf("%d",iSum); getch(); return 0; } Given #include<stdio.h> #include<conio.h> int main(void) { int iSum,iCtr,iNum; for(iSum=0,iCtr=0; iCtr<10;iCtr=iCtr+1){ printf("Enter mark: "); scanf("%d",&iNum); iSum=iSum+iNum; } printf("%d",iSum); getch(); return 0; }

59. Quitting the Loops – break Statement The break statement is used to: Force thetermination of a loop. When a break statement is encountered in a loop, the loop terminates immediately and the execution resumes the next statementfollowing the loop. Note: Break statement can be used in an if statement only when the if statement is written in a loop Just an if statement with break leads to compilation error in C

60. What is the output of the following code snippet? int iCounter1=0; int iCounter2; while(iCounter1 < 3) { for (iCounter2 = 0; iCounter2 < 5; iCounter2++) { printf("%d",iCounter2); if (iCounter2 == 2){ break; } } printf(""); iCounter1 += 1; } 0 1 2 0 1 2 0 1 2

62. In case of for loop, continue makes the execution of the increment portion of the statement and then evaluates the conditional part.

63. In case of while and do-while loops, continue makes the conditional statement to be executed.Example: for(iCount = 0 ; iCount < 10; iCount++) { if (iCount == 4) { continue; } printf(“%d”, iCount); } The above code displays numbers from 1 to 9 except 4.

64. Comparison of break, continue and exit

65. What is the output of the following code snippet? 1 2 3 4 5 6 7 8 9 Case 1: Case 3: 1 3 5 7 9 iCount = 1; do { printf(“%d”,iCount); iCount++; if (iCount == 5) { continue; } } while(iCount < 10); for (iCount=1;iCount <= 10; iCount++) { if (iCount % 2 == 0) { continue; } printf(“%d”,iCount); } Case 4: Case 2: for (iCount=1;iCount <= 5; iCount++) { for (iValue =1; iValue <= 3; iValue++) { if (iValue == 2) { break; } printf(“%d”,iValue); } } iCount = 1; while (iCount < 10) { if (iCount == 5) { continue; } printf(“%d”,iCount); iCount++; } 1 2 3 4 1 1 1 1 1

67. A ‘while’ loop is used when the number of times the loop gets executed is not known and the loop should not be executed when the condition is initially false