reading a file and writing appending c code example

Example 1: c write to file

#include <stdio.h>
#include <stdlib.h>

int main() {
    char sentence[1000];

    // creating file pointer to work with files
    FILE *fptr;

    // opening file in writing mode
    fptr = fopen("program.txt", "w");

    // exiting program 
    if (fptr == NULL) {
        printf("Error!");
        exit(1);
    }
    printf("Enter a sentence:\n");
    fgets(sentence, sizeof(sentence), stdin);
    fprintf(fptr, "%s", sentence);
    fclose(fptr);
    return 0;
}

Example 2: c program to read and write to a file

/*Program to read from file using getc() function*/
#include <stdio.h>
int main() {
 FILE *fp;
 char ch;
 /*Open file in read mode*/
 fp= fopen ('example.txt', 'r');
 while( (ch = getc(fp)) != EOF) {
  /*getc() function reads a character and its value is stored in variable 'ch' until EOF is encountered*/
  printf('%ch', ch);
 }
  fclose(fp);
  return 0;
}

Example 3: file in C

//to open a file
FILE=*fp;
fp=fopen("one.txt", "w");
//to close file 
fclose(fp);