C program to Create a text file input.txt and Print the contents of file in reverse order.

Write a ‘C’ program to do the following.
> Create a text file ‘input.txt’
> Print the contents of file in reverse order.

#include<stdio.h>
#include<conio.h>
void main()
{
 FILE *fp,*ft;
 char ch,name[80];
 int i=0;
 clrscr();
 fp=fopen("input.txt","r");
 if(fp==NULL)
 {
   printf("File Does Not Exist");
   exit(0);
 }
 ft=fopen("b.txt","w");
 if(ft==NULL)
 {
   printf("File Does Not Exist");
   exit(0);
 }
 while(1)
 {
  ch=fgetc(fp);
  if(ch!=' ')
  {
    name[i]=ch;
    i++;
  }
  else
  {
    strrev(name);
    fputs(name,ft);
    i=0;
   }
  if(ch==EOF)
  {
    break;
  }
 }
 fclose(fp);
 fclose(ft);
 getch();
}

C program to accept string from user and convert all lower case letters into upper case and vice-versa.

Write a ‘C’ program to accept string from user and convert all lower case letters into upper case and vice-versa.

#include<stdio.h>
#include<conio.h>
void main()
{
  char name[80];
  int l,i;
  clrscr();
  printf("Enter the String");
  gets(name);
  l=strlen(name);
  for(i=0;i<l;i++)
  {
    if(islower(name[i]))
    {
      printf("%c",toupper(name[i]));
    }
    else  if(isupper(name[i]))
    {
      printf("%c",tolower(name[i]));
    }
    else
    {
      printf("%c",name[i]);
    }
  }
  getch();
 }