1.

#include<stdio.h>
main()
{
    FILE *fp;char filename[20];
    char ch;
    printf("Enter file name : ");
    gets(filename);
    fp = fopen(filename, "w");
    if (fp == NULL)
    {
        printf("Could not open file ");
    }
    printf("Enter content to be written in file : ");
    while((ch=getchar())!='\n')
    {
        fputc(ch,fp);
    }
    fclose(fp);
}