Question

****C PROGRAMMING****

(100 points) Write a program that prompts the user to enter the name of a file. The program encoded sentences in the file and writes the encoded sentences to the output file.

Enter the file name: messages.txt

Output: encoded words are written to file: messages.txt.swt

The program reads the content of the file and encodes a sentence by switching every alphabetical letter (lower case or upper case) with alphabetical position i, with the letter with alphabetical position 25 – i. For example, letter a is at position 0 and after encoding it becomes letter z (position 25). Letter m is at position 12, it becomes letter n (position 13) after encoding because 25 – 12 is 13.

1. Name your program file_encode.c. The output file name should be the same name as the input file but with an added extension of .swt. For example, if the original file name is abc.txt, the output file name is then abc.txt.swt. Assume the file name is no more than 100 characters. Assume the length of each line in the input file is no more than 100 characters. Assume the input file contains no more than 1000 lines.

2. In the program, you should include the following function. void line_switch(char *s1, char *s2);

The function expects s1 to point to a string containing the input as a string and stores the output to the string pointed by s2.

Answer 1

Program

#include <stdio.h>
#include <ctype.h>
#define WORD_LEN 100

int read_line(char *str, int n);

void line_switch(char *message, char *shift_message);

int main()
{
    int shift_amount;
    char sen1[WORD_LEN+1];
    char sen2[WORD_LEN+1];
    FILE *fp,*fp1;
    char word[100],ch;
    fp = fopen("messages.txt","r");
    fp1 = fopen("messages.txt.swt","w+");
    if ( fp )
   {
    while(!feof(fp))//this loop searches the for the current word
{
    fscanf(fp,"%s",sen1);
    line_switch(sen1, sen2);
    fprintf(fp,"%s",sen2);

}
   }

    else
      {
         printf("Failed to open the file\n");
    }
   fclose(fp);
     fclose(fp1);

    return 0;
}

void line_switch(char *message, char *shift_message)
{

    for(; *message != '\0'; message++)
    {

             if(*message >= 'a' && *message <= 'z')
             *shift_message++ = (25-(*message - 'a') )% 26 + 'a';
          else if(*message >= 'A' && *message <= 'Z')
             *shift_message++ = (25-(*message - 'A' ))% 26 + 'A';
          else
            *shift_message++ = *message;
    }

    *shift_message='\0';
}