Question:Write a c program to know read/write permission of given file. 

#include "time.h"
#include "sys\stat.h"
#include "stdio.h"
void main(){
    struct stat status;
    FILE *fp;
    stat("test.txt",&status);
    clrscr();
    if (status.st_mode & S_IREAD)
         printf("You have read permission.\n");
    if (status.st_mode & S_IWRITE)
         printf("You have write permission.");
    getch();

}

Question:Write a c program to know the last date of modification of any file 

#include "time.h"
#include "sys\stat.h"
#include "stdio.h"
int main(){
    struct stat status;
    FILE *fp;
    fp=fopen("test.txt","r");
    fstat(fileno(fp),&status);
    
    printf("Last date of modification : %s",ctime(&status.st_ctime));
    return 0;
}

Question:Write a c program to find out the size and drive where file has stored of any given file? 

#include "time.h"
#include "sys\stat.h"
#include "stdio.h"
int main(){
    struct stat status;
    FILE *fp;
    fp=fopen("test.txt","r");
    fstat(fileno(fp),&status);
    printf("Size of file : %d",status.st_size);
    printf("Drive name   : %c",65+status.st_dev);
    return 0;
}

Question:How to use complex numbers in c 

#include<stdio.h>
int main(){
int a,b;

printf("Enter any complex number in the format a+ib: ");
scanf("%d+i%d",&a,&b);

printf("Real part is: %d",a );
printf("\nImaginary part is: %d",b);

return 0;

}

Question:C program to printf complex numbers 

#include<stdio.h>
int main(){
int a,b;

printf("Enter the real part of complex number: ");
scanf("%d",&a);

printf("Enter the imaginary part of complex number: ");
scanf("%d",&b);

printf("\nComplex number is: %d%+di",a,b );

return 0;

}

Question:C program to add two complex numbers 

#include<stdio.h>
int main(){
  int a,b,c,d,x,y;
  printf("\nEnter the first complex number:");
  scanf("%d%d",&a,&b);
  printf("\nEnter the second complex number:");
  scanf("%d%d",&c,&d);
  if(b<0)
      printf("%d-i\n",a-b);
  else
      printf("d+i\n",a+b);
  if(d<0)
      printf("d-i\n",c-d);
  else
      printf("%d+i\n",c+d);
  printf("\nADDITION ");
  x=a+c;
  y=b+d;
  if(y>0)
      printf("%d-i%d",x,-y);
  else
      printf("%d+i%d",x,+y);
  printf("\n\nSUBTRACTION ");
  x=a-c;
  y=b-d;
  if(y<0)
      printf("%d-i%d",x,-y);
  else
      printf("%d+i%d",x,+y);
  return 0;
}

Question:Sum of 1 + 2 + ….  + n series in c programming language 

#include<stdio.h>
int main(){

    int n,i;
    int sum=0;

    printf("Enter the n i.e. max values of series: ");
    scanf("%d",&n);

    sum = (n * (n + 1)) / 2;

    printf("Sum of the series: ");

    for(i =1;i <= n;i++){
         if (i!=n)
             printf("%d + ",i);
         else
             printf("%d = %d ",i,sum);
         }
   
    return 0;
}
Sample output:
Enter the n i.e. max values of series: 5
Sum of the series: 1 + 2 + 3 + 4 + 5 = 15

Question:Sum of 1^2 + 2^2 + …. + n^2 series in c programming language 

#include<stdio.h>

int main(){

    int n,i;
    int sum=0;

    printf("Enter the n i.e. max values of series: ");
    scanf("%d",&n);

    sum = (n * (n + 1) * (2 * n + 1 )) / 6;

    printf("Sum of the series : ");

    for(i =1;i<=n;i++){
         if (i != n)
             printf("%d^2 + ",i);
         else
             printf("%d^2 = %d ",i,sum);
    }

    return 0;
}
Sample output:
Enter the n i.e. max values of series: 5
Sum of the series: 1^2 + 2^2 + 3^2 + 4^2 + 5^2 = 55

Question:Write a c program or code to find out the sum of series 1^3 + 2^3 + …. + n^3 that is sum of cube of n natural numbers. 

#include<stdio.h>
#include<math.h>

int main(){

    int n,i;
    int sum=0;

    printf("Enter the n i.e. max values of series: ");
    scanf("%d",&n);

    sum = pow(((n * (n + 1) ) / 2),2);

    printf("Sum of the series : ");

    for(i =1;i<=n;i++){
         if (i != n)
             printf("%d^3 + ",i);
         else
             printf("%d^3 = %d ",i,sum);
    }

    return 0;
}
Sample output:
Enter the n i.e. max values of series: 3
Sum of the series: 1^3 + 2^3 + 3^3 = 36

Question:Write a c program to find out the sum of in A.P. series 

#include<stdio.h>
#include<math.h>

int main(){

    int a,d,n,i,tn;
    int sum=0;

    printf("Enter the first number of the A.P. series: ");
    scanf("%d",&a);

    printf("Enter the total numbers in the A.P. series: ");
    scanf("%d",&n);

    printf("Enter the common difference of A.P. series: ");
    scanf("%d",&d);

    sum = ( n * ( 2 * a + ( n -1 ) * d ) )/ 2;
    tn = a + (n-1) * d;
    printf("Sum of the series A.P.: ");

    for(i=a;i<=tn; i= i + d ){
         if (i != tn)
             printf("%d + ",i);
         else
             printf("%d = %d ",i,sum);
    }

    return 0;
}
Sample output:
Enter the first number of the A.P. series: 1
Enter the total numbers in the A.P. series: 5
Enter the common difference of A.P. series: 3
Sum of the series: 1 + 4 + 7 + 10 + 13 = 35