Introduction to C programming

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                                      CHAPTER - 1

what is C ?

C is a general-purpose programming language created by Dennis Ritchie at the Bell Laboratories in 1972.
  • A basic programming language is C. Of all the languages, this one is used for programming the most.  
  • C is a fundamental language in which we can write in whole operating system.

Why Learn C ?

  • It is one of the most popular languages ​​in the world.
  • After learning this language, we will not have any problem in learning any other programming language.

  • Like Java ,JavaScript, C++,Python etc. Their syntax is similar.
  • c language is faster than other programming languages. Like Java, Python.

Get Started C Language

         To start two thing:

  • A text editor, like Notepad, To write C code
  • A compiler GCC, to translate a C code to Machine Language.

Install IDE(integrated Development environment)IDE is that which provides all facilities required by a programmer for developing software on a single Screen.

  • There are many IDE includes : Visual studio code, code: :Block, Devpp.
  • But it is popular in Visual studio code.

            C syntax



Line 1. #include<stdio.h> is a header file library. Its work is input output function.

Line 2. The Next part C program is to declare main() this is a function. Any code inside the curly bracket {} will execute.

         Line 3. printf is a  function used that prints text on the output screen.

          Line4. return 0  ends the main() function.


   Some of C Header files:

  • Stddef.h - Describes several useful types and macros.
  • Stdint.h - identifies precise width integer types.
  • Stdio.h - specifies core input and output function.
  • Stdlib.h - Defines numeric conversion function, pseudo-random network generator,memory allocation.
  •  String.h - Defines string handling function.
  • Math.h - Defines common mathematics function.        

            

    C Output (print Text)

  • To output values and print text, it utilizes the printf function.

Example



Double Quotes

  • Text must be enclosed in double quotation marks (" ") when working with it.
  • If you forget the double quotes, an error occurs:

New Lines

  • To insert the new line , use the \n (backslash) character.

Example




  • Multiple lines can also be used in a single printf function.

Example

  • #include<stdio.h>
  • int main()
    {
        printf("hello world\n I am learning C\nAnd it is Awesome");
        return 0;
    }

Escape Sequence Description                      

\t                                Creates a horizontal tab

\\                                 Insert a backslash character (\)

\”                                 Insert a double quotes character



  •  We use comments to test alternative code since they help to clarify the code and make it more readable.
  • Comments can be single line and multiple lines.

Single line comments

  • Two forward slashes (//) welcome single line comments.

  • Text between // forward slash the end of ignore by the compiler will not execute.

        Example

    // This is comment
    printf("Hello world");
  • This example uses a single line comment.

Example

  •     printf("Hello world");     // This is comment
       

Multi line Comments

  • Multi line comment start with /* and end with */.
  • Text between /* and */ ignore the compiler.

Example

  •       */The code will printf in Hello world into the screen*/

                                              CHAPTER - 2

Variables

  • The data values, such as numbers and alphabets, are stored in a variable.

Different types of variable (define different keyword), For example;

  • int - store integer (whole Number),without decimals, Example - 123,-123.
  • float - Store floating point Number, With decimals, Example - 19.99,-19.99.
  • char - store single character , Example - ‘a’ , ’d’ character will under single quotes.

 

Variables naming Rules:

  • Variables name is any combination of alphabet, digit and underscore.
  •  No other symbol is allowed.
  • Valid variable names cannot start with a digit.

Output Variables 

  • In many other programming languages ​​like Python, Java, C++ we use print function to get the value of variables but this is not possible in C.

C Format Specifier

Format specifier to be used together  with the printf () function to tell the compiler what type of data the variable is storing.it is basically a placeholder for the variable value.

  • Format specifiers start with a percentage sign %. And, it follows the character.
  • To output the value of an int variable, we use the format specifier %d within double quotes in the printf function.

Example:
int x = 15;
    printf("%d",x);
  • To print other types, use char for %c , float for %f.

Example
int main()
{
    int myNum = 15; //integer(whole Number)
    float myfloatNum = 19.99; //floating point Number
    char myLetter = 'a'; // character
    // print variables
    printf("%d",myNum);
    printf("%f",myfloatNum);
    printf("%c",myLetter);
}

  • To combine both text and variables, separate with the commas inside the printf function.
int x = 15;  
  printf("My favorite number is: %d",x);

Variables Related Programs:

  • This is int variables program.

#include<stdio.h>
int main()
{
    int x = 10;
    int y = 20;
    printf("%d%d\n",x,y);
    return 0;
}

Output
10
20
  • This is float program.
#include<stdio.h>
int main()
{
    float x = 9.9;
    float y = 10.6;
    printf("%f%f",x + y);
    return 0;
}

Output
19.79

char program.
#include<stdio.h>
int main(){
    char x = 'a';
    char y = 'b';
    printf("%c%c\n",x,y);
    return 0;
}

Output
a,b

#include<stdio.h>
int main()
{
    // student data
    int studentid = 123;
    int studentage = 18;
    float studentfees = 2500.00;

    // print variablrs
    printf("student id: %d\n",studentid);
    printf("student age%d\n",studentage);
    printf("student fees%f\n",studentfees);
    return 0;
}

C Data Types:

A variables in C specified data type and use a format specifier inside the printf function to display it:

Example
#include<stdio.h>
int main()
{
 // Create variables
int myNum = 5;             // Integer (whole number)
float myFloatNum = 5.99;   // Floating point number
char myLetter = 'D';       // Character

// Print variables
printf("%d\n", myNum);
printf("%f\n", myFloatNum);
printf("%c\n", myLetter);

}

Output
5
5.99
D

Basic Data types

Variables are stored according to the size and type of the data that specifies it.

Data size Description Example
Type

int 4 bytes store whole number , without decimals 1

float 4 bytes store fractional number, with decimals. store 1.99
in 6 to 7 decimals number.

double 8 bytes store fractional number, with decimals. storing 1.98
upto 15 decimal digits

char 1 bytes Store a single character / letter / number. 'A"
Basic Format Specifier Data Type

%d int

%f or %F float

%If double

%c char


C character Data types:

A single character can be stored using the char data type.

Example :
char myGrade = 'A';
printf("%c", myGrade);

Example :

char a = 65, b = 66, c = 67;
printf("%c", a);
printf("%c", b);
printf("%c", c);

Example :

char myText = 'Hello';
printf("%c", myText);



C Numeric Data Types

Numeric Types

When you need to store a whole number (without decimals), such as 35 or 1000, use int. When you need to store a floating point number (with decimals), such as 9.99 or 3.14515, use float or double.

int

int myNum = 100;
printf("%d",myNum);

float 

float myNum = 9.99;
printf("%f",myNum);

double

double myNum = 19.99;
printf("%1f",myNum);

Float vs double

float - Seven- and six-digit numbers can be stored in floating-point variables. Four bytes are used by Float.

double - We can store 15-digit values in double variables. Memory used by double is 8 bytes.

C Data type example

#include<stdio.h>
int main()
{
    // create variables in data types
    int item = 50;
    float cost per item = 9.99;
    float total cost = item * cost per item;
    char = 'a';
    // print variables//
    printf("Number of items: %d\n", items);
    printf("Cost per item: %.2f %c\n", cost_per_item, currency);
    printf("Total cost = %.2f %c\n", total_cost, currency);
    return 0;

}

C Constants

If you change the value of existing variables then use the const keyword.

Example

const int my Num = 15; // myNum is always is 15
myNum  = 10; // assigment can read only variables myNum

Example

const int minutesperhour = 60;
const float pi = 3.15;

Example

const int minutesperhour;

This is not work;

const int minutesperhour;
minutesperhour = 60;

                                              CHAPTER - 3


C Operator

Operator are used to perform operation on variables and values.

Arithmetic Instruction

An instruction which is used to manipulate data using operator is
known as arithmetic instruction.

Unary Operator

The unary operator only accepts one data as input. unary operator
commonly known as increment and decrement operator are used .
only single variables used.

  • Pre increment Operator ++x , --x. 
  • Post increment Operator x++ , x--.

Unary Operator Types:
  • Increment Operators
  • Decrement Operators
Increment Operator
  • Operators for increments like ++x and x++. And they increase by the value of one.
Pre increment:

#include<stdio.h>
int main()
{
    int x = 10, y = 20;
    int p = ++x + ++y;
    printf("%d\n",x);
    printf("%d\n",y);
    printf("%d\n",p);
    return 0;
}

Output

11
21
32

Post increment:

#include<stdio.h>
int main()
{
    int x = 20;
    int y = 40;
    int p = x++ + y++;
    printf("%d\n",x);
    printf("%d\n",y);
    printf("%d\n",p);
    return 0;
}

Output

21
41
60

Decrement Operator
  • Operators for increments like --x and x--. And they Decrease by the value of one.

Pre increment:

#include<stdio.h>
int main()
{
    int x = 10, y = 20;
    int p = --x - --y;
    printf("%d\n",x);
    printf("%d\n",y);
    printf("%d\n",p);
    return 0;
}

Output

9
19
- 10

Post increment:

#include<stdio.h>
int main()
{
    int x = 10, y = 20;
    int p = x-- - y--;
    printf("%d\n",x);
    printf("%d\n",y);
    printf("%d\n",p);
    return 0;
}

Output

9
19
- 10

#include<stdio.h>
int main()
{
    int a = 10, b = 100;
    float c = 10.5, d = 100.5;
    printf("++a = %d\n",++a);
    printf("--b = %d\n",--b);
    printf("++c = %d\n",++c);
    printf("--d = %d\n",--d);
    return 0;
}

Output

++a = 11
--b = 99
++c = 0
--d =0

Binary Operators:

Binary operators are operators that take two operands or data.

Binary Operators Types:

  • Arithmatic Operators
  • Logical Operators
  • Relational Operators
  • Bit wise Operators
  • Assignment Operators
Arithmetic Operators:

Arithmetic Operators   Example

+ (Addition)                      A+B
- (Subtraction)                  A-B
* (Multiplications)           A*B 
/ (Division)                       A/B
% (Modulus)                    A%B

Note - C language real constants not the apply modulus.

Related Programs:

#include<stdio.h>
int main()
{
    int x = 10;
    int y = 20;
    printf("%d",x+y);
    return 0;
}

#include<stdio.h>
int main()
{
    int a = 10;
    int b = 20;
    int c ;
    c = a+b;
    printf("a+b = %d\n",c);
    c = a-b;
    printf("a-b = %d\n",c);
    c = a*b;
    printf("a*b = %d\n",c);
    c = a/b;
    printf("a/b = %d\n",c);
    return 0;

}

Output
a+b = 30
a-b = -10
a*b = 200
a/b = 0

Note - Two integer will be perform operation also answer is integer.

Logical Operators

Logical operators can also used to test True aur False value.
 
Operators    Name          Description                                                                                     
&& AND Logical AND Operator. It both Operands
                                                            are non zero ,condition become True.

||                      OR             Logical OR Operator. It both operands 
are non zero , condition become True.

! NOT Logical NOT Operator. If condition True.
But, Logical NOT Operator it is make in False.

Relational Operators

Relational Operators are used to compare two values. This is important in programming, because it helps find answer and decisions.

Operators     Name                         Description      

< less than if the value of the left operands
is less than the values of the right
operands . if yes then the condition
become true.

> Greater than if the value of the left operands
is Greater than the values of the right
operands . if yes then the condition
become true.

<= less than equal if the value of the left operands
is less than or equal to the values of the right
operands. If yes then the condition
become true.

>= Greater than equal the value of the left operands is greater than or equal to
the values of the right operands. if yes then the condition become true.
== Equal to If two operands have equal value then the condition is                                                             true otherwise it is false.
                                         
!= Not equal to if the value of two operands are equal
or not. if the value are not equal then the
condition become true.

Bitwise Operators

Operator           Name              Description
&                        Bitwise AND       Sets each bit to 1 if both bits are 1
 |                          Bitwise OR           Sets each 2 bit  is 1 the result come as 1
^                        Bitwise XOR        Sets each bit to 1 if only one of the bits is 1
~             Bitwise NOT       Inverts all the bits (flips 1s to 0s and 0s to 1s)
<<                       Left Shift                  Shifts bits to the left by the specified number of positions
>>            Right Shift           Shifts bits to the right by the specified number of positions

  CHAPTER 4

CONDITIONAL STATEMENTS

A conditional statement allows you to execute various code blocks based on whether a particular condition is true OR false.

  1. IF Statement.
  • syntax:
if(condition)
{
    //code to executed if the condition is true
}
  • Example:
#include<stdio.h>
int main()
{
    int age;
    printf("enter age ");
    scanf("%d",&age);

    if(age > 18)
    {
        printf("adult \n");

    }
else{
printf("not adult");
}
    return 0;
}

else

In a specific block of code, we use the else statement। When the condition is false, it is performed.

Syntax

if{

}
else:{
   
}

Example:

#include<stdio.h>
int main()
{
    int a = 5;
    printf("enter a number ")
    scanf("%d",&a):
    if(a>0)
    {
        printf("the number is positive");
    }
    else if(a<0)
    {
        printf("the number is negative");
    }
    else{
        printf("the number is zero");
    }
    }
    return 0;



#include<stdio.h>
int main()
{
    int x;
    printf("enter a number ")
    scanf("%d",&x);
    if(x%5==0)
    {
        printf("divisible by 5");
    }
    else{
        printf("not divisible by 5");
    }
    getch();
}


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