Question:C code for Determinant of 2X2 matrix 

#include<stdio.h>
int main(){
  int a[2][2],i,j;
  long determinant;

  printf("Enter the 4 elements of matrix: ");
  for(i=0;i<2;i++)
      for(j=0;j<2;j++)
           scanf("%d",&a[i][j]);

  printf("\nThe matrix is\n");
  for(i=0;i<2;i++){
      printf("\n");
      for(j=0;j<2;j++)
           printf("%d\t",a[i][j]);
  }

  determinant = a[0][0]*a[1][1] - a[1][0]*a[0][1];

  printf("\nDeterminant of 2X2 matrix: %ld",determinant);
 
   return 0;
}
Sample Output:
Enter the 4 elements of matrix: 4
8
3
9

The matrix is

4       8
3       9

Determinant of 2X2 matrix: 12

Question:C code for Determinant of 3X3 matrix 

#include<stdio.h>

int main(){

  int a[3][3],i,j;

  long determinant;



  printf("Enter the 9 elements of matrix: ");
  for(i=0;i<3;i++)
      for(j=0;j<3;j++)
           scanf("%d",&a[i][j]);

  printf("\nThe matrix is\n");
  for(i=0;i<3;i++){
      printf("\n");
      for(j=0;j<3;j++)
           printf("%d\t",a[i][j]);
  }

  determinant = a[0][0]*((a[1][1]*a[2][2]) - (a[2][1]*a[1][2])) -a[0][1]*(a[1][0]*a[2][2] - a[2][0]*a[1][2]) + a[0][2]*(a[1][0]*a[2][1] - a[2][0]*a[1][1]);

  printf("\nDeterminant of 3X3 matrix: %ld",determinant);
 
   return 0;
}
Sample output:
Enter the 9 elements of matrix: 1
2
3
4
5
6
7
8
9

The matrix is

1       2       3
4       5       6
7       8       9

Determinant of 3X3 matrix: 0

Question:C program to write to a file 

#include<stdio.h>
int main(){
FILE *fp;
char ch;
fp=fopen("file.txt","w");
printf("\nEnter data to be stored in to the file:");
while((ch=getchar())!=EOF)
putc(ch,fp);
fclose(fp);
return 0;
}

Question:COPY DATA FROM ONE FILE TO ANOTHER FILE USING C PROGRAM 

#include<stdio.h>
int main(){
  FILE *p,*q;
  char file1[20],file2[20];
  char ch;
  printf("\nEnter the source file name to be copied:");
  gets(file1);
  p=fopen(file1,"r");
  if(p==NULL){
      printf("cannot open %s",file1);
      exit(0);
  }
  printf("\nEnter the destination file name:");
  gets(file2);
  q=fopen(file2,"w");
  if(q==NULL){
      printf("cannot open %s",file2);
      exit(0);
  }
  while((ch=getc(p))!=EOF)
      putc(ch,q);
  printf("\nCOMPLETED");
  fclose(p);
  fclose(q);
 return 0;
}

Question:DISPLAY SOURCE CODE AS OUTPUT IN C PROGRAM 

#include<stdio.h>
int main(){
    FILE *p;
    char ch;
    p=fopen("raja.c","r");
    while((ch=getc(p))!=-1)
         putchar(ch);
    fclose(p);
    return 0;
}

Question:How to read a text file by c program 

#include<stdio.h>
int main(){
char str[70];
FILE *p;
if((p=fopen("string.txt","r"))==NULL){
printf("\nUnable t open file string.txt");
exit(1);
}
while(fgets(str,70,p)!=NULL)
puts(str);
fclose(p);
return 0;
}

Question:Writing of entire array to a file using c program 

#include<stdio.h>
int main(){
  FILE *p;
  int i,a[10];
  if((p=fopen("myfile.dat","wb"))==NULL){
      printf("\nUnable to open file myfile.dat");
      exit(1);
  }
  printf("\nEnter ten values, one value on each line\n");
  for(i=0;i<10;i++)
      scanf("%d",&a[i]);
  fwrite(a,sizeof(a),1,p);
  fclose(p);
  return 0;
}

Question:Concatenate many files and store them in a file in c programming language 

#include<stdio.h>
 void concatenate(FILE *fp1,FILE *fp2,char *argv[],int argc);
 int main(int argc,char *argv[]){
   FILE *fp1,*fp2;
   concatenate(fp1,fp2,argv,argc);
   return 0;
 }

void concatenate(FILE *fp1,FILE *fp2,char **argv,int argc){
   int i,ch;
   fp2=fopen("files","a");
   for(i=1;i<argc-1;i++){
      fp1=fopen(argv[i],"r");
      while((ch=getc(fp1))!=EOF)
      putc(ch,fp2);
   }
 }

Question:C program to get total file  size 

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

Question:Write a c program to know given file is regular file, character special or it is directory? 

#include "time.h"
#include "sys\stat.h"
#include "stdio.h"
void main(){
    struct stat status;
    FILE *fp;
    stat("c:\\tc\\bin",&status);
    clrscr();
    if (status.st_mode & S_IFDIR)
         printf("It is directory.\n");
    if (status.st_mode & S_IFCHR)
         printf("It is chracter file.");
    if (status.st_mode & S_IFREG)
         printf("It is reggular file.");
    getch();
}
Output: It is directory.