1. Unit VI- Selection – Making Decisions, Repetition

2. Control statements in C language

3. if break continue goto switch Control statements Conditional Ternary
Sequential
Branching
Conditional if
switch
Ternary
Unconditional
goto
break
continue
Looping
for
while
do -while

4. Decision Making and Branching

5. *conditional statement *goto statement
contents
*if statement
*switch
*conditional statement
*goto statement

6. if-statement conditional branching statement Types of if statements
* Simple-if
* if- else
*Nested if-else
* if-else ladder

7. simple-if The general form:( with compound statement) if( condition) {}
statement-x;

8. A block if statement may be modeled as:
if (A>0) {
A=A+1;
Print A;
B=A+2; }
Yes
A>0
A=A+1
Print A
B=A+2

9. simple-if if( condition) statement-1; statement-2; statement-3;
×The general form:( without compound statement)
if( condition)
statement-1;
statement-2;
statement-3;
statement-x;

10. If statements can be modeled as a flow chart.
if (A>0)
print A
Print A
Yes
A>0 No

11. The following is a segment of program: x=1; y=1; if(n>0) x=x+1;
y=y+1;
printf("x=%d\ny=%d\n",x,y);
What will be values of x and y if n assumes a value of
1. n=1
2.n=0
OUTPUT:
n=1  x=2 y=2
n=0  x=1 y=2

12. The following is a segment of program: x=1; y=1; if(n>0) { x=x+1;
y=y+1; }
printf("x=%d\ny=%d\n",x,y);
What will be values of x and y if n assumes a value of
1. n=1
2.n=0
OUTPUT:
N=1  x=2 y=2
N=0  x=1 y=1

13. if-else The general form:- if(condition) { true block statements; }
false block statements;
statement-x;

14. Flowchart of if-else statement.
Print A is greater
Yes
A>0
Print A is not greater No

15. C-Program using if-else
Program to accept a character in any case and print in another case without using character test functions

16. # include <stdio.h>
# include <conio.h>
main( ) {
char ch,c1;
clrscr( );
printf("enter a char in anycase:");
ch=getchar();
if(ch>=65 && ch<=90)
c1=ch+32;
else
if(ch>=97 && ch<=122)
c1=ch-32;
printf("the given char in another case IS:");
putchar(c1);
getch(); }

17. Nesting of if-else if-else statements in nested form
if(test condition-1) {
if( test-condition-2)
statement-1; }
else
statement-2;
statement-3;
statement-x;

18. program using nested if-else
*write a c-program to find largest of three numbers using nested if-else statements.

19. if(a>b) { if(a>c) printf("%d",a); else printf("%d",c); }
#include<stdio.h>
#include<conio.h>
main() {
int a,b,c;
printf("enter three numbers \n");
scanf("%d%d%d",&a,&b,&c);
printf("\n largest value is: " );
if(a>b) {
if(a>c)
printf("%d",a);
else
printf("%d",c); }
if(c>b)
printf("%d",b);
getch();

20. The else-if ladder if( condition-1) statement-1; else if( condition-2)
The general form
if( condition-1)
statement-1;
else if( condition-2)
statement-2;
else if( Condition-3)
statement-3;
else if( condition n)
statement-n;
else
default-statement;
Statement-x;

21. C-programs using else-if ladder
Write a c-program to grade the students according to following rules using else-if ladder.
avgmarks grade
80 to Honours
60 to First Division
50 to Second Division
40 to Third Division
0 to Fail

22. Else-if Logic flow.

23. Lab program-1
1. Design, develop and execute a program in C to find and output all the roots of a given quadratic equation, for non-zero coefficients.

24. Algorithm to find roots of quadratic equation
STEP 1: INPUT THE VALUES FOR a,b,c
Input a,b,c
STEP 2: DETERMINE DISCRIMINANT
Discriminant = b*b – (4*a*c)
STEP 3: FIND TWO EQUAL ROOTS
If Discriminant = 0 then
Roots X1=X2=-b/(2*a)
Print the two equal roots

25. STEP 4: FIND TWO DISTINCT ROOTS
If Discriminant > 0 then
X1 = -b + sqrt(Discriminant) / (2*a)
X2 = -b – sqrt(Discriminant) / (2*a)
Print the two distinct roots

26. STEP 5: FIND COMPLEX ROOTS
If Discriminant < 0 then
Real part = - b / (2 *a)
Imaginary Part = sqrt(abs(disc)) / (2*a)
Print the imaginary roots in the form of Real part + i Imaginary part and
Real part - i Imaginary part.
STEP 6: STOP

27. #include<stdio. h> #include<conio. h> #include<math
#include<stdio.h> #include<conio.h> #include<math.h> main() { float a,b,c,d,root1,root2,rpart,ipart; printf("Enter the three co-effients\n"); scanf("%f%f%f",&a,&b,&c);
6/18/2018
Dept of CSE,DSCE

28. d=(b. b-4. a. c); if(d==0) { printf("Roots are equal\n"); root1=-b/2
d=(b*b-4*a*c); if(d==0) { printf("Roots are equal\n"); root1=-b/2*a; root2=root1; printf("root1=%f\nroot2=%f\n",root1,root2); }
6/18/2018
Dept of CSE,DSCE

29. else if(d>0) { printf("Roots are real & distinct\n"); root1=(-b+sqrt(d))/(2*a); root2=(-b-sqrt(d))/(2*a); printf("root1=%f\nroot2=%f\n",root1,root2); }
6/18/2018
Dept of CSE,DSCE

30. else { printf("Roots are imaginary\n"); rpart=-b/(2
else { printf("Roots are imaginary\n"); rpart=-b/(2*a); ipart=sqrt(fabs(d))/(2*a); printf("root1=%f+i%f\n",rpart,ipart); printf("root2=%f-i%f\n",rpart,ipart); } getch();
6/18/2018
Dept of CSE,DSCE

31. Multiway Selection
In addition to two-way selection, most programming languages provide another selection concept known as multiway selection.
Multiway selection chooses among several alternatives.
C has two different ways to implement multiway selection:
the switch statement
else-if construct.

32. Switch is a composite statement used to make a decision between many alternatives. The format is:
Switch Statement.

33. Program to demonstrate the use of Switch Statement.

34. Results

35. Switch With Break Statements
Break statements is used to execute only one of the case label sequences.
Break Statements causes the program to jump out of the switch statement and follow the code following after the switch statement.

36. Program Modified With Break Statements

37. Flow chart of Switch(With Break) Statement.

38. Results

39. Rules while using Switch Statements

40. example switch(choice) //valid if choice is integer variable.
switch(i+1) //valid if i is integer variable
switch(i+2.1) //invalid even if i is integer
2 or more case labels with same value is not allowed
case 1:printf(“hello:”); break;
case 1:printf(“lll”);break; //invalid
case 10+2: //valid
case i+2: //invalid Since i variable is present
case4: //invalid since no space between case and 4.
Case 1: //invalid case should be in lowercase
case 1:2:3: //invalid there should be separate case for each.

41. Write a c program to design a simple calculator using switch

42. #include<stdio.h>
#include<conio.h>
#include<process.h>
main() {
float a,b,res;
char op;
printf(“Enter the operator\n”);
op=getchar( );
printf("Enter two operands\n");
scanf("%f%f", &a, &b);
switch(op)
case '+':
res = a + b;
break;

43. case '-':
res=a-b;
break;
case '*':
res=a*b;
case '/':
if(b!=0)
res=a/b;
else {
printf("Divide by zero error"); }
default: printf("Illegal operator\n");
printf("%f%c%f=%f",a,op,b,res);
getch();

44. goto statement Unconditional branching statement
This statement is used to transfer the control from one point to another point anywhere in the program.
The goto requires a label in order to identify the place where the branch is to be made.
A label is any valid variable name

45. The general forms of goto
goto label; label:
statement-1; statement-1;
statement-2; statement-2;
label: statement-3;
statement-x; goto label;
Forward jump backward jump

46. Assuming x=5,y=0,z=0.what is the value of z after execution of the following code
if(x===0 ||x&&y) if(!y) z=1; else z=2; z=3; (A) 0 (B)1 (c ) 2 ( D) 3

47. Problems on switch
Assuming that x=2,y=1 and z=0 initially ,what will be their values after executing the following code segments?
switch(y) {
case 2: x=1;
y=x+1;
case 3: x=0;
break;
default: x=1;y=0; }

48. switch(y) {
case 0: x=0;
y=0;
case 2: x=2;z=2;
default: x=1;y=2; }

49. For the following program segment give an equivalent program segment using the switch statement
if(opr==1) res=a+b; else if (opr==2) res=a-b; else if(opr==3) res=a*b; else res=a/b; Feb-March/2005 (6 marks)

50. Write a C-program to find roots of quadratic equation using switch.

51. #include<stdio. h> #include<conio. h> #include<math
#include<stdio.h> #include<conio.h> #include<math.h> main() { int a,b,c,d,m; float root1,root2,ipart,rpart; printf("Enter three co-effients\n"); scanf("%d%d%d",&a,&b,&c);

52. d=(b*b-4*a*c); if(d==0) m=1; else if(d>0) m=2; else m=3;

53. switch(m) {
case 1:printf("Roots are equal\n");
root1=-b/(2*a);
printf("root1=root2=%f",root1);
break;
case 2:printf("Roots are real & distinct\n");
root1=(-b+sqrt(d))/(2*a);
root2=(-b-sqrt(d))/(2*a); printf("root1=%f\nroot2=%f",root1,root2); break;

54. case 3:printf("Roots are imaginary\n"); rpart=-b/(2
case 3:printf("Roots are imaginary\n"); rpart=-b/(2*a); ipart=sqrt(fabs(d))/(2*a); printf("root1=%f+i%f\n",rpart,ipart); printf("root2=%f-i%f\n",rpart,ipart); break; default:printf("Invalid opeartion\n"); } getch();

55. C-Skills

56. Program to print "Hello, world" without using semicolon (;) in your program
main() {
if (printf ("Hello, world\n")) }

57. What is the ouput?
int x; x=printf(“welcome\n”); printf(“%d”,x);

58. What is the ouput?
int x=65; Printf(“%d\n”,printf(“%d”,x);

59. Which is better?
X++ OR X=x+1

60. Solution x++ generates inc instruction
x = x + 1 generates inc followed by move instruction

61. Find out errors? If any
#include<stdio.h> #include<conio.h> int main( ) { int a=--2; printf(“ a=%d”,a); getch(); }

62. Find out output?
int x=7,p=2; printf(“%d%d%d”,x++,x,--p); printf(“%d%d%d”,p,p++,++p);