C Programming
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•
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IF-ELSE
SWITCH
LOOPS
Selection: the if statement
if ( condition )
{
statement(s)
}
/* body of the if statement */
if ( TRUE )
{
/* between the braces is the body of the if statement */
Execute all statements inside the body
}
Concatenated If-else Statements
if (expr1)
statement1
else if (expr2)
statement2
else if (expr3)
statement3
else if (expr4)
statement4
/*do this if expr1 is non-zero*/
/*i.e., expr1 == 0, expr2 != 0*/
/expr1 and expr2 are zero, expr3 != 0*/
/expr1, expr2 , expr3 all zero, expr4 != 0*/
else
statement5
/*i.e., all expr are zero*/
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Concatenated If-else Statements
• Last else is always attached to last if
• If it should be attached to any other if, use {} to
control the flow of execution. if{ (Condition1)
Syntax for Nested
IF-ELSE
Statement
if(Condition2)
{
Statement1;
}
else
{
Statement2;
}
}
else
{
if(Condition3)
{
Statement3;
}
else
{
Statement4;
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}
}
Example -1 for IF Statement
• Write a C program for asking the user to enter a number and to
check and display whether the entered number is odd or even.
• Note That:
– Use the modulus operator.
– The number must be entered from the user like “Enter a Number=“
– Display the result like “5 is an Odd Number” or “6 is an Even Number”
int main(int argc, char *argv[]) {
int num;
printf("Enter a number :");
scanf("%d",&num);
if(num%2==0)
{
printf(“%d is an even number“, num);
}
else
{
printf(“%d is an odd number“, num);
}
return 0;
}
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Example -4 for IF Statement
• Write a C program to convert Fahrenheit to Celsius and Celsius to
Fahrenheit.
• Note That:
–
–
–
–
You must ask the choice for conversion from the user.
Find the converted temperature based on given input
You must use only two variables for the selection and the temperature.
The variables “temp” and “sel” must be used for the temperature and the
choice, respectively.
– For from Fahrenheit to Celsius: (temp - 32) / 1.8
– For from Celsius to Fahrenheit: (temp*1.8)+32;
– Display the result like:
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float temp;
int sel;
printf("Enter a temperature=");scanf("%f",&temp);
printf("For From Fahrenheit to Celsius [1]\n");
printf("For From Celsius to Fahrenheit [2]\n");
printf("Enter Your Choice (1 or 2)=");scanf("%d",&sel);
if(sel==1)
{
printf("The Temperature in Celsius is %0.3f",(temp-32)/1.8);
}
else
{
printf("The Temperature in Fahrenheit is %0.3f",(temp*1.8)+32);
}
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Switch
– The syntax of switch statement is
switch (expression) {
case const-expression1 : statement1
case const-expression2 : statement2
:
default : statementn
}
– All case expressions must be different.
– Expression must evaluate to an integer.
– First the expression is evaluated. Then the value of expression is compared with
the case expressions. The execution begins at the case statement, whose case
expression matches.
– All the statements below are executed.
– If default is present and if no other case matches then default statement is
executed.
Fixed Program using Switch-Case Structures
int a,b,c,sel ;
printf("\n 1. Press 1 for addition");
printf("\n 2. Press 2 for subtraction");
printf("\n Enter your choice="); scanf("%d", &sel);
switch(sel)
{
case 1:
printf("Enter 2 numbers=");
scanf("%d%d", &a, &b);
c = a + b;
printf("The Result=%d", c);
break;
case 2:
printf("Enter 2 numbers=");
scanf("%d%d", &a, &b);
c = a - b;
printf("The result=%d", c);
break;
default:
printf("you have passed a wrong key");
}
Switch Example
• What is the output of program below:
int main(int argc, char *argv[]) {
int num;
num=1;
switch(num)
{
case 1:printf("A");
case 2:printf("B");
case 3:printf("C");
default:printf("D");
}
return 0;
}
Switch Statement Example
int month, daysInMonth, leapYear;
…
switch (month) {
case 0:
printf("January\n");
daysInMonth = 31;
break;
case 1:
printf("February\n");
daysInMonth = leapYear ? 29 : 28;
break;
case 2:
printf("March\n");
daysInMonth = 31;
break;
case 3:
printf("April\n");
daysInMonth = 30;
break;
…
expression 1 ? expression 2 : expression 3
} // switch
where
•expression1 is Condition 18
•expression2 is Statement Followed if Condition is True
•expression3 is Statement Followed if Condition is False
Example -1 for SWITCH Statement
• Write a C program which is a menu-driven program based on simple
calculation like addition, subtraction, multiplication and division
according to user's choice
• Note That:
–
–
–
–
You must use switch statement.
The numbers must be entered from the user like “Enter Two Numbers:“
The four basic operation of arithmetic is selected by the user.
The output of the program must be displayed like the below
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ANSWER for Example 1
int main(int argc, char *argv[]) {
float n1, n2, res; char choice, ch;
printf("1.Addition\n");
printf("2.Subtraction\n");
printf("3.Multiplication\n");
printf("4.Division\n");
printf("5.Exit\n\n");
printf("Enter Your Choice : "); scanf("%c",&choice);
switch(choice)
{
case '1' : printf("Enter two number : ");scanf("%f%f",&n1,&n2);
case '2' : printf("Enter two number : "); scanf("%f%f",&n1,&n2);
case '3' : printf("Enter two number : "); scanf("%f%f",&n1,&n2);
case '4' : printf("Enter two number : "); scanf("%f%f",&n1,&n2);
case '5' : exit(0);break;
default : printf("Wrong Choice..!!"); break;
}
printf("\n------------------------------------\n");
return 0;
}
res=n1+n2; printf("Result = %f",res); break;
res=n1-n2; printf("Result = %f",res); break;
res=n1*n2; printf("Result = %f",res); break;
res=n1/n2; printf("Result = %f",res); break;
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Repetition Structure
• A repetition structure allows the programmer to
specify that an action is to be repeated while some
condition remains true.
• There are three repetition structures in C, the
while loop, the for loop, and the do-while loop.
The while Repetition Structure
while ( condition )
{
statement(s)
}
while (TestExpression)
{
// the body of the loop
}
• The while loop evaluates the TestExpression inside the parentheses ().
• If TestExpression is true, statements inside the body of while loop are executed.
Then, TestExpression is evaluated again.
• The process goes on until TestExpression is evaluated to false.
• If TestExpression is false, the loop terminates (ends).
while Loop Example
• Problem: Write a program that calculates the average exam grade
for a class of 5 students.
• What are the program inputs?
– the exam grades
• What are the program outputs?
– the average exam grade
• The Output must be like:
Answer
int main(int argc, char *argv[]) {
int counter=1, total=0, grade;
// average=(float)total/5;
float average;
while(counter<=5)
{
printf("Enter The grade for %d.student=",counter);
scanf("%d",&grade);
total+=grade;
counter+=1;
}
average=total/5.0;
printf("The Class Average For Ten Grades is %.2f",average);
return 0;
}
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while Loop Example
• The Same Problem:
Write a program that calculates the average exam grade for a class.
Note That:
– You must use a sentinel value to control your while loop
– The sentinel value is tested and then the loop is executed with regard to “true”
or “false”.
– The sentinel value you will use is “-1” that is referred to as priming read.
– You must use four variables at most.
– The output must be like:
Answer
int main(int argc, char *argv[]) {
int counter=0,total=0,grade;
float average;
printf("Enter a grade=");scanf("%d",&grade);
while(grade!=-1)
{
total+=grade;
printf("Enter a grade=");scanf("%d",&grade);
counter+=1;
}
average=(float)total/counter;
printf("The Class Average For %d Grades is %.2f",counter,average);
return 0;
}
while Loop Example
Write a program that prints star patterns on the screen up to a certain row.
Note That:
–
–
–
–
–
–
You must use while statement for the loop.
The total number of stars must be entered from the user.
A number of certain row must be entered from the user.
All rows contain the same number of stars’.
You consider that the row number is important for this problem
The output must be like:
Answer
int main(int argc, char *argv[]) {
int totalstar, totalrow, i=1, j=1;
printf("How many stars you want to print ? ");
scanf("%d", &totalstar);
printf("Upto how many rows ? ");
scanf("%d", &totalrow);
int number_star_a_row=totalstar/totalrow;
while(i<=totalrow)
{
while(j<=number_star_a_row)
{
printf("* ");
j++;
}
printf("\n");
j=1;i++;
}
return 0;
}
The Problem but;
Write a program that prints star patterns on the screen up to a row.
Note That:
–
–
–
–
–
You must use while statement for the loop.
The total number of stars must be entered from the user.
A number of row must be entered from the user.
You can consider that the row number is NOT important for this problem
The output must be like:
Answer
int main(int argc, char *argv[]) {
int totalstar, totalrow, i=1, j=1;
while(i<=totalrow)
{
while(j<=number_star_a_row)
{
printf("* ");
j++;
}
printf("\n");
j=1;i++;
}
int lacknum=totalstar-number_star_a_row*totalrow;
i=1;while(i<=lacknum){printf("* ");i++;
}
return 0;
}
Questions?
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