1. Basics of “C” Programming
By
R.Sivagami, Assistant Professor
Department of Computer Science and Applications
D.K.M College for women(Autonomous), Vellore-1.

2. TOPICS COVERED
 Data types
 Type Conversion
 Conditional statements

3. Data types:
A data type specifies the type of data that a variable can store .

4. Format Specifiers

5. Set decimal Precision
While printing a floating point number, the output will show many digits
after the decimal point:
Example:
float myFloatNum = 3.5;
double myDoubleNum = 19.99;
printf("%fn", myFloatNum); // Outputs 3.500000
printf("%lf", myDoubleNum); // Outputs 19.990000
To remove the extra zeros (set decimal precision), we can use a dot (.) followed by
a number that specifies how many digits that should be shown after the decimal
point:
Example:
float myFloatNum = 3.5;
printf("%fn", myFloatNum); // Default will show 6 digits after the decimal point
printf("%.1fn", myFloatNum); // Only show 1 digit
printf("%.2fn", myFloatNum); // Only show 2 digits
printf("%.4f", myFloatNum); // Only show 4 digits

6. Type Conversion
Converting the value of one data type to another type is known as type conversion.
There are two types of conversion in C:
Implicit Conversion (automatically)
Explicit Conversion (manually)
For example, try to divide two integers, 5 by 2, you would expect the result to be 2.5.
But since we are working with integers (and not floating-point values), the following
example will just output 2:
Example:
int x = 5;
int y = 2;
int sum = 5 / 2;
printf("%d", sum); // Output 2

7. Implicit Conversion
Implicit conversion is done automatically by the compiler when you assign a value of one
type to another.
Assign an int value to a float type:
Example:
// Automatic conversion: int to float
float myFloat = 9;
printf("%f", myFloat); // 9.000000
The compiler automatically converts the int value 9 to a float value of 9.000000.
Another Example:
// Automatic conversion: float to int
int myInt = 9.99;
printf("%d", myInt); // 9

8. Explicit Conversion
Explicit conversion is done manually by placing the type in parentheses () in front
of the value.
Example
// Manual conversion: int to float
float sum = (float) 5 / 2;
printf("%f", sum); // 2.500000
Example2:
int num1 = 5;
int num2 = 2;
float sum = (float) num1 / num2;
printf("%f", sum); // 2.500000

9. Conditional Statements
C has the following conditional statements:
 if - To specify a block of code to be executed, if a specified condition
is true
 Else - To specify a block of code to be executed, if the same condition
is false
 else if - To specify a new condition to test, if the first condition is false
 switch - To specify many alternative blocks of code to be executed


10. if Statement
 Use the if statement to specify a block of code to be executed if a condition
is true.
Syntax:
if (condition) {
// block of code to be executed
//if the condition is true
}

11. Examples
EX1:
if (20 > 18) {
printf("20 is greater than 18");
}
Ex2:
int x = 20;
int y = 18;
if (x > y) {
printf("x is greater than y");
}

12. The else Statement
The else statement is used to specify a block of code to be executed if the
condition is false.
Syntax:
if (condition)
{
// block of code to be executed if the condition is true
}
else
{
// block of code to be executed if the condition is false
}

13. Examples
 Ex1:
 int time = 20;
if (time < 18) {
printf("Good day.");
} else {
printf("Good evening.");
}
// Outputs "Good evening.“

14. Ex2: Program to check whether a given number is
even or odd.
#include <stdio.h>
#include <stdlib.h>
int main() {
int n;
printf("Enter a number:");
scanf("%d", &n);
if (n % 2 == 0) {
printf("%d is even number", n);
} else {
printf("%d is a odd number", n);
}
return 0;
}

15. The else if Statement
The else if is used to specify a new condition if the first condition is false.
Syntax:
if (condition1) {
// block of code to be executed if condition1 is true
} else if (condition2) {
// block of code to be executed if the condition1 is false and condition2 is
true
} else {
// block of code to be executed if the condition1 is false and condition2 is
false
}

16. Flow chart:

17. Ex1:
int time = 22;
if (time < 10) {
printf("Good morning.");
} else if (time < 20) {
printf("Good day.");
} else {
printf("Good evening.");
}
// Output "Good evening."

18. Program to find if a number is Positive or
Negative:
int myNum = 10; // Is this a positive or negative number?
if (myNum > 0) {
printf("The value is a positive number.");
} else if (myNum < 0) {
printf("The value is a negative number.");
} else {
printf("The value is 0.");
}

19. Switch Statement
 Switch case statement evaluates a given expression and based on the evaluated
value(matching a certain condition), it executes the statements associated with
it. Basically, it is used to perform different actions based on different
conditions(cases).
 Switch case statements follow a selection-control mechanism and allow a value
to change control of execution.
 They are a substitute for long if statements that compare a variable to several
integral values.
 The switch statement is a multi way branch statement. It provides an easy way to
dispatch execution to different parts of code based on the value of the
expression.
 In C, the switch case statement is used for executing one condition from
multiple conditions. It is similar to an if-else-if ladder.

20. Syntax of switch Statement
switch(expression)
{
case value1: statement_1;
break;
case value2: statement_2;
break;
. . .
case value_n: statement_n;
break;
default: default_statement;
}

21. Rules of the switch case statement
 Following are some of the rules that we need to follow while using the
switch statement:
 In a switch statement, the “case value” must be of “char” and “int” type.
 There can be one or N number of cases.
 The values in the case must be unique.
 Each statement of the case can have a break statement. It is optional.
 The default Statement is also optional.

22. // C program to Demonstrate returning of day based numeric // value
#include <stdio.h>
int main()
{
// switch variable
int var = 1;
// switch statement
switch (var) {
case 1:
printf("Case 1 is Matched.");
break;
case 2:
printf("Case 2 is Matched.");
break;
case 3:
printf("Case 3 is Matched.");
break;
default:
printf("Default case is Matched.");
break;
}
return 0;
}
Output:
Case 1 is Matched.

23. Program for practice
1) Write a C program to find maximum between two numbers.
2) Write a C program to find maximum between three numbers.
3) Write a C program to check whether a number is negative, positive or
zero.
4) Write a C program to check whether a number is divisible by 5 and 11 or
not.
5) Write a C program to check whether a year is leap year or not.

24. THANK YOU