/*C program to check whether a number entered by user is prime or not using function with no arguments and no return value*/
#include <stdio.h>
void prime();
int main(){
    prime();      //No argument is passed to prime().
    return 0;
}
void prime(){  
/* There is no return value to calling function main(). Hence, return type of prime() is void */
    int num,i,flag=0;
    printf("Enter positive integer enter to check:\n");
    scanf("%d",&num);
    for(i=2;i<=num/2;++i){
        if(num%i==0){
             flag=1;
         }
    }
    if (flag==1)
        printf("%d is not prime",num);
    else
       printf("%d is prime",num);  
    }

/*C program to check whether a number entered by user is prime or not using function with no arguments but having return value */
#include <stdio.h>
int input();
int main(){
    int num,i,flag;
    num=input();     /* No argument is passed to input() */
    for(i=2,flag=i;i<=num/2;++i,flag=i){
    if(num%i==0){
        printf("%d is not prime",num);
        ++flag;
        break;
    }
    }
    if(flag==i)
        printf("%d is prime",num);
    return 0;
}
int input(){   /* Integer value is returned from input() to calling function */
    int n;
    printf("Enter positive enter to check:\n");
    scanf("%d",&n);
    return n;
}

/*Program to check whether a number entered by user is prime or not using function with arguments and no return value */
#include <stdio.h>
void check_display(int n);
int main(){
    int num;
    printf("Enter positive enter to check:\n");
    scanf("%d",&num);
    check_display(num);  /* Argument num is passed to function. */
    return 0;
}
void check_display(int n){     
/* There is no return value to calling function. Hence, return type of function is void. */
    int i,flag;
    for(i=2,flag=i;i<=n/2;++i,flag=i){
    if(n%i==0){
        printf("%d is not prime",n);
        ++flag;
        break;
    }
    }
    if(flag==i)
        printf("%d is prime",n);
}

/* Program to check whether a number entered by user is prime or not using function with argument and return value */
#include <stdio.h>
int check(int n);
int main(){
    int num,num_check=0;
    printf("Enter positive enter to check:\n");
    scanf("%d",&num);
    num_check=check(num); /* Argument num is passed to check() function. */
    if(num_check==1)
       printf("%d in not prime",num);
    else
       printf("%d is prime",num);
    return 0;
}
int check(int n){   
/* Integer value is returned from function check() */ 
    int i;
    for(i=2;i<=n/2;++i){
    if(n%i==0)
        return 1;
}
   return 0;
}

#include <stdio.h>
int sum(int n);
int main(){
    int num,add;
    printf("Enter a positive integer:\n");
    scanf("%d",&num);
    add=sum(num);
    printf("sum=%d",add);
}
int sum(int n){
    if(n==0)
       return n;
    else
       return n+sum(n-1);    /*self call  to function sum() */
}

Enter a positive integer:
5
15

sum(5)
=5+sum(4)
=5+4+sum(3)
=5+4+3+sum(2)
=5+4+3+2+sum(1)
=5+4+3+2+1+sum(0)
=5+4+3+2+1+0
=5+4+3+2+1
=5+4+3+3
=5+4+6
=5+10
=15

float a[2][6];

int c[2][3]={{1,3,0}, {-1,5,9}};
                 OR
int c[][3]={{1,3,0}, {-1,5,9}};
                 OR 
int c[2][3]={1,3,0,-1,5,9};

double cprogram[3][2][4]={ 
{{-0.1, 0.22, 0.3, 4.3}, {2.3, 4.7, -0.9, 2}},
 {{0.9, 3.6, 4.5, 4}, {1.2, 2.4, 0.22, -1}},
 {{8.2, 3.12, 34.2, 0.1}, {2.1, 3.2, 4.3, -2.0}} 
};

#include <stdio.h>
int main(){
   float a[2][2], b[2][2], c[2][2];
   int i,j;
   printf("Enter the elements of 1st matrix\n");
/* Reading two dimensional Array with the help of two for loop. If there was an array of 'n' dimension, 'n' numbers of loops are needed for inserting data to array.*/   
   for(i=0;i<2;++i)      
       for(j=0;j<2;++j){
       printf("Enter a%d%d: ",i+1,j+1);
       scanf("%f",&a[i][j]);
       }
   printf("Enter the elements of 2nd matrix\n");
   for(i=0;i<2;++i)
       for(j=0;j<2;++j){
       printf("Enter b%d%d: ",i+1,j+1);
       scanf("%f",&b[i][j]);
       }
   for(i=0;i<2;++i)
       for(j=0;j<2;++j){
/* Writing the elements of multidimensional array using loop. */
       c[i][j]=a[i][j]+b[i][j];  /* Sum of corresponding elements of two arrays. */
       }
   printf("\nSum Of Matrix:");
   for(i=0;i<2;++i)
       for(j=0;j<2;++j){
       printf("%.1f\t",c[i][j]);  
           if(j==1)             /* To display matrix sum in order. */
              printf("\n");
      }
return 0;
}

Enter the elements of 1st matrix
Enter a11: 2;
Enter a12: 0.5;
Enter a21: -1.1;
Enter a22: 2;
Enter the elements of 2nd matrix
Enter b11: 0.2;
Enter b12: 0;
Enter b21: 0.23;
Enter b22: 23;

Sum Of Matrix:
2.2     0.5
-0.9    25.0

#include <stdio.h>
void display(int a)
   {
   printf("%d",a);
   }
int main(){
   int c[]={2,3,4};
   display(c[2]);  //Passing array element c[2] only.
   return 0;
}

4

#include <stdio.h>
float average(float a[]);
int main(){
     float avg, c[]={23.4, 55, 22.6, 3, 40.5, 18};
     avg=average(c);   /* Only name of array is passed as argument. */
     printf("Average age=%.2f",avg);
     return 0;
   }
float average(float a[]){ 
     int i;
     float avg, sum=0.0;
     for(i=0;i<6;++i){
       sum+=a[i];
     }
     avg =(sum/6);
     return avg;
}

Average age=27.08

#include 
void Function(int c[2][2]);
int main(){
   int c[2][2],i,j;
   printf("Enter 4 numbers:\n");
   for(i=0;i<2;++i)
      for(j=0;j<2;++j){
           scanf("%d",&c[i][j]);
      }
   Function(c);   /* passing multi-dimensional array to function */
   return 0;
}
void Function(int c[2][2]){
/* Instead to above line, void Function(int c[][2]){ is also valid */
   int i,j;
   printf("Displaying:\n");
   for(i=0;i<2;++i)
      for(j=0;j<2;++j)
          printf("%d\n",c[i][j]);
}

Enter 4 numbers:
2
3
4
5
Displaying:
2
3
4
5

/* Example to demonstrate use of reference operator in C programming. */
#include <stdio.h>
int main(){
  int var=5;
  printf("Value: %d\n",var);
  printf("Address: %d",&var);  //Notice, the ampersand(&) before var.
  return 0;
}

Value: 5 
Address: 2686778

scanf("%d",&var);

data_type * pointer_variable_name;
int *p;

/* Source code to demonstrate, handling of pointers in C program */
#include <stdio.h>
int main(){
   int *pc,c;
   c=22;
   printf("Address of c:%d\n",&c);
   printf("Value of c:%d\n\n",c);
   pc=&c;
   printf("Address of pointer pc:%d\n",pc);
   printf("Content of pointer pc:%d\n\n",*pc);
   c=11;
   printf("Address of pointer pc:%d\n",pc);
   printf("Content of pointer pc:%d\n\n",*pc);
   *pc=2;
   printf("Address of c:%d\n",&c);
   printf("Value of c:%d\n\n",c);
   return 0;
}

Address of c: 2686784
Value of c: 22

Address of pointer pc: 2686784
Content of pointer pc: 22

Address of pointer pc: 2686784
Content of pointer pc: 11

Address of c: 2686784
Value of c: 2

int *pc, c;

c=22;

pc=&c;

c=11 ;

*pc=2;

int c, *pc;
pc=c;  /* pc is address whereas, c is not an address. */
*pc=&c; /* &c is address whereas, *pc is not an address. */