What is C ?

  • C is a structured Programming language​

  • C is case sensitive

​

}

4 different names

  • name

  • Name

  • NAME

  • naMe

​

What is C ?

#include <stdio.h>

int main ()
{
  //print something
  printf("Welcome to C");
}

header

main function

comment

body

Comments​

​

Single line comment​

 

​

​

Multi line comment​

​

​

/* This is 
a multi line
comment*/
      //single line comment

Data types

  •  int – integer values​
  •  char – single character values  (' ')​
  • float – float values
  • double – double values

Storage size and format specifiers ​

Data Types​ Storage size​
( bytes)		 printf( )
conversion specification		 scanf( )
conversion specification​
int​ 2 or 4 %d %d
char​ 1 %c %c
float​ 4 %f %f
double 8 %f %f

Print 

#include <stdio.h>

int main() {

    printf("Hello world!");
    
    return 0;
}
#include <stdio.h>

int main() {

    int a;
    
    scanf("%d", &a);
    printf("%d",a);
    
    return 0;
}

get user input & print

Variables​

         ​

 

(Memory locations)

  • Initialization​​      

#include <stdio.h>

int main() {

    int number;

}
#include<stdio.h>
int main()
{
    int number = 10;
}

Data type           variable name

int                               x  ;

  • Declaration​

Data type   variable name       value

int                    x                   =      10;  

Variable Names – Rules​

                  Underscore(_)                        ​

                     Capital Letters ( A – Z )                       ​

                     Small Letters ( a – z )                         ​

                     Digits ( 0 – 9 )     ​

 

  • Should not be a reserved word ​

  • Should start with a letter or an underscore​

  • No other special charaters are allowed including space, commas​

  • Variable names are case sensitive​

  • Use allowed Characters

Operators

+   

-

/

*

  • Arithmetic

#include <stdio.h>

int main() {

int a = 20;
int b = 10;


printf("addition is: %d  \n",a+b);

printf("substraction is: %d  \n",a-b);

printf("multiplication is: %d  \n",a*b);

printf("division is: %d  \n",a/b);

}

Arithmetic operators (example)

Output

addition is: 30
substraction is: 10
multiplication is: 200
division is: 2

Operators

<

>

<=

>=

==

!=

 

  • Relational

less than

Greater than

less than or equal to

Greater than or equal to

is equal to

is not equal to

#include <stdio.h>

main() {

   int a = 21;
   int b = 10;
   int c ;

   if( a == b ) {
      printf("Line 1 - a is equal to b\n" );
   }
   else {
      printf("Line 1 - a is not equal to b\n" );
   }
 
   if ( a < b ) {
      printf("Line 2 - a is less than b\n" );
   }
   else {
      printf("Line 2 - a is not less than b\n" );
   }
 
   if ( a > b ) {
      printf("Line 3 - a is greater than b\n" );
   }
   else {
      printf("Line 3 - a is not greater than b\n" );
   }
   
   /* Lets change value of a and b */
   a = 5;
   b = 20;
 
   if ( a <= b ) {
      printf("Line 4 - a is either less than or equal to  b\n" );
   }
 
   if ( b >= a ) {
      printf("Line 5 - b is either greater than  or equal to b\n" );
   }
}
Output

Line 1 - a is not equal to b
Line 2 - a is not less than b
Line 3 - a is greater than b
Line 4 - a is either less than or equal to  b
Line 5 - b is either greater than  or equal to b

Relational operators (example)

Operators

&&

 

||

 

!

 

  • Logical  

AND

OR

NOT

#include <stdio.h>

main() {

   int a = 5;
   int b = 20;
   int c ;

   if ( a < 10 && b < 100 ) {
      printf("Line 1 - Condition is true\n" );
   }
 
   if ( a > 10 || b >10 ) {
      printf("Line 2 - Condition is true\n" );
   }
   
   /* lets change the value of  a and b */
   a = 8;
   b = 10;
 
   if ( a > 10 && b > 20 ) {
      printf("Line 3 - Condition is true\n" );
   }
   else {
      printf("Line 3 - Condition is not true\n" );
   }
 
   if ( !(a <10) && (b > 5) ) {
      printf("Line 4 - Both conditions are true\n");
   }
   else
   {
      printf("Line 4 - Both conditions are true. \n" 
      "But, status is inverted as false\n");
   }
 
}
Output

Line 1 - Condition is true
Line 2 - Condition is true
Line 3 - Condition is not true
Line 4 -  Both conditions are true. 
But, status is inverted as false

Logical operators

(example)

Operators

+=

=*

-=

/=

%=

&=

 

 

  • Assignment

|=

<<=

>>=

^=

 

 

  • Assignment (continued)

#include <stdio.h>

main() {

   int a = 6;
   int c ;

   c =  a;
   printf("Line 1 - =  Operator Example, Value of c = %d\n", c );

   c +=  a;
   printf("Line 2 - += Operator Example, Value of c = %d\n", c );

   c -=  a;
   printf("Line 3 - -= Operator Example, Value of c = %d\n", c );

   c *=  a;
   printf("Line 4 - *= Operator Example, Value of c = %d\n", c );

   c /=  a;
   printf("Line 5 - /= Operator Example, Value of c = %d\n", c );

   c  = 200;
   c %=  a;
   printf("Line 6 - %= Operator Example, Value of c = %d\n", c );

   c <<=  2;
   printf("Line 7 - <<= Operator Example, Value of c = %d\n", c );

   c >>=  2;
   printf("Line 8 - >>= Operator Example, Value of c = %d\n", c );

   c &=  2;
   printf("Line 9 - &= Operator Example, Value of c = %d\n", c );

   c ^=  2;
   printf("Line 10 - ^= Operator Example, Value of c = %d\n", c );

   c |=  2;
   printf("Line 11 - |= Operator Example, Value of c = %d\n", c );

}
 Output

Line 1 - =  Operator Example, Value of c = 6
Line 2 - += Operator Example, Value of c = 12
Line 3 - -= Operator Example, Value of c = 6
Line 4 - *= Operator Example, Value of c = 36
Line 5 - /= Operator Example, Value of c = 6
Line 6 - %= Operator Example, Value of c = 2
Line 7 - <<= Operator Example, Value of c = 8
Line 8 - >>= Operator Example, Value of c = 2
Line 9 - &= Operator Example, Value of c = 2
Line 10 - ^= Operator Example, Value of c = 0
Line 11 - |= Operator Example, Value of c = 2

Assignment operators (example)

Operators

Sizeof ()

&

*

?;

 

 

  • Misc 

-  Conditional Expression

 

-  Returns the size of a variable (Bytes)

-  Returns the address of a variable

-  Pointer to a variable


#include <stdio.h>

main() {

   int a = 4;
   short b;
   double c;
   int* ptr;

   /* example of sizeof operator */
   printf("Line 1 - Size of variable a = %d\n", sizeof(a) );
   printf("Line 2 - Size of variable b = %d\n", sizeof(b) );
   printf("Line 3 - Size of variable c= %d\n", sizeof(c) );

   /* example of & and * operators */
   ptr = &a; /* 'ptr' now contains the address of 'a'*/
   printf("value of a is  %d\n", a);
   printf("*ptr is %d.\n", *ptr);

   /* example of ternary operator */
   a = 10;
   b = (a == 1) ? 20: 30;
   printf( "Value of b is %d\n", b );

   b = (a == 10) ? 20: 30;
   printf( "Value of b is %d\n", b );
}
 Output

Line 1 - Size of variable a = 4
Line 2 - Size of variable b = 2
Line 3 - Size of variable c= 8
value of a is  4
*ptr is 4.
Value of b is 30
Value of b is 20

Misc operators (example)

Increment / Decrement

  • pre increment    -     ++a  ;

  • post increment  -     a++  ;

  • pre decrement   -      --a   ;

  • post decrement -      a--   ;

pre    -   changes before using it in a expression

post  -   changes after using it in a expression

#include <stdio.h>

int main() 
{ 
    int x = 10; 
    int a; 
  
    a = ++x; 
    //Pre Increment Operation
  
    // Value of a will change 
    printf("%d"  \n, a);
  
    // Value of x change before execution of a=++x; 
    printf("%d", x);
  
    return 0; 
} 
 Output

11
11

Pre increment (example)

#include <stdio.h>

int main() 
{ 
    int x = 10; 
    int a; 
  
    a = x++; 
    //Post Increment Operation
  
    //  Value of a will not change 
    printf("%d"  \n, a);
  
    // Value of x change after execution of a=x++;
    printf("%d", x);
  
    return 0; 
} 
 Output

10
11

Post increment (example)

Loops

  • iteration

  • 3 types

  1. For

  2. While

  3. Do While

1. For Loop

for ( initialization ; condition checking ; increment )​

{​

    set of statment​

}​

for(int a = 5 ; a < 10 ; a++)

{
     printf("Hello World");
}

2. While Loop

while( condition )​

{​

    Statement ;​

}

#include <stdio.h>


int main()
{
int i = 1;
    
    while (i <= 5)
    {
        printf("%d\n", i);
        i++;
    }
return 0;
}

3. DoWhile Loop

do​

{​

   Set of statement ;​

} while ( condition ) ;​

int x = 1;

do{

   printf("%d\n", x);

   x++;

} while(x <= 5);

while ( )  VS do while ( )

Conditional Statement​    if / else

​

If (condition)​

{​

   //execution if condition is true​

   Statement 1 ;              ​

} ​

else​

{​

   //execution if condition is false​

   Statement 2 ;​

}

// Check whether an integer is odd or even

#include <stdio.h>
int main() {
    int number;
    printf("Enter an integer: ");
    scanf("%d", &number);

    // True if the remainder is 0
    if  (number%2 == 0) {
        printf("%d is an even integer.",number);
    }
    else {
        printf("%d is an odd integer.",number);
    }

    return 0;
}

if / else (example)

switch ( var )​

{​

case 1 :   //statements​
                  break;​

​

case 2 :    // statement ;​

                    break ;​

​

case 3 :     //statement ;​

                    break ;​

​

default  :    // default statements​                    ​      ​

}​

Switch case


#include <stdio.h>

int main () {

   char grade;
   
   scanf("%c",&grade);

   switch(grade) {
      case 'A' :
         printf("Excellent!" );
         break;
      case 'B' :
         printf("Well done" );
         break;
      case 'C' :
         printf("You passed" );
         break;
      case 'F' :
         printf("Better try again" );
         break;
      default :
         printf("Invalid grade" );
   }
}

Conditional statement (example)

Functions

Functions

  1. Inbuilt Functions
  2. User Defined Functions
#include<stdio.h>

int main()
{
   //statment
}

int area(int x,int result)
{
     //statment
      return 0;
}

return type

Parameters

Function name

1. Inbuilt Functions

#include <stdio.h>

int main(){
	
	//isalpha( ) function in C language checks 
    //whether given character is alphabetic or not	
 
   char ch;
 
   printf("Enter any character\n");
   scanf("%c", &ch);
   
   if ( isalpha ( ch ) )
      printf ( "\nEntered character is alphabetic" ) ;
   else
      printf ( "\nEntered character is not alphabetic" ) ;
}

No return type no parameters

No return type with parameters

With return type no parameters

With return type with parameters

2. User Defined Functions

#include<stdio.h>

void myFunction();       // function declaration


int main()
{
    myFunction();        // function call
    return 0;
}

void myFunction()        // function definition
{
   //your code
}

No return type no parameters 

#include<stdio.h>

void greatNum();       // function declaration

int main()
{
    greatNum();        // function call
    return 0;
}

void greatNum()        // function definition
{
    int i, j;
    printf("Enter 2 numbers that you want to compare...");
    scanf("%d%d", &i, &j);
    if(i > j) {
        printf("The greater number is: %d", i);
    }
    else {
        printf("The greater number is: %d", j);
    }
}

No return type with parameters 

#include<stdio.h>

void greatNum(int a, int b);       // function declaration

int main()
{
    int i, j;
    printf("Enter 2 numbers that you want to compare...");
    scanf("%d%d", &i, &j);
    greatNum(i, j);        // function call
    return 0;
}

void greatNum(int x, int y)        // function definition
{
    if(x > y) {
        printf("The greater number is: %d", x);
    }
    else {
        printf("The greater number is: %d", y);
    }
}

With return type no parameter

#include<stdio.h>

int greatNum();       // function declaration

int main()
{
    int result;
    result = greatNum();        // function call
    printf("The greater number is: %d", result);
    return 0;
}

int greatNum()        // function definition
{
    int i, j, greaterNum;
    printf("Enter 2 numbers that you want to compare...");
    scanf("%d%d", &i, &j);
    if(i > j) {
        greaterNum = i;
    }
    else {
        greaterNum = j;
    }
    // returning the result
    return greaterNum;
}

with return type with parameters

#include<stdio.h>

int greatNum(int a, int b);       // function declaration

int main()
{
    int i, j, result;
    printf("Enter 2 numbers that you want to compare...");
    scanf("%d%d", &i, &j);
    result = greatNum(i, j); // function call
    printf("The greater number is: %d", result);
    return 0;
}

int greatNum(int x, int y)        // function definition
{
    if(x > y) {
        return x;
    }
    else {
        return y;
    }
}

An array is a variable that can store multiple values

Array index start with 0

data type  array name [array size]

int          number             [5] ;

How to declare an array ?

1

0

2

3

4

index

element

Arrays

#include<stdio.h>

int main()
{
  int array [5] = { 5, 10, 8, 2, 4, 12 };

// printing elements of an array
  for(int i = 0; i < 5; ++i) {
     printf("%d\n", numbers[i]);
  }
}
#include <stdio.h>

int main() {
  int array[5];

  printf("Enter 5 integer numbers: ");

  // taking input and storing it in an array
  for(int i = 0; i < 5; i++) {
     scanf("%d", &array[i]);
  }
  
  printf("Print numbers\n ");

  // print it
  for(int i = 0; i < 5; i++) {
     printf("%d\n", array[i]);
  }
  return 0;
}

Take 5 inputs from user and store them in a array and print the array

Two Dimensional Arrays

[0,0] [0,1] [0,2] [0,3]
[1,0] [1,1] [1,2] [1,3]
[2,1] [2,1] [2,2] [2,3]
[3,0] [3,1] [3,2] [3,3]

column

row

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C Programming

By Lakindu Kariyawasam

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C Programming

This is a beginner guide to understand C programming language concepts and theories. #DiveIntoC #FOSSNSBM

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