FILE I/O: two file pointes : <p>I'm new to FILE I/O Stream and I want to write a program, which converts chars (read from "texti.txt") like "ä,Ä,ü,Ü,ö,Ö" to "ae,Ae,ue,Ue,oe,Oe" and write them in a new file called "texto.txt".</p>

<p><strong>First Question:</strong>
Is it ok to have two file pointers (on to each file) at the same time like i do?</p>

<p><strong>Second Question:</strong>
What am I doing wrong with character compare in the switch statement?
VS2015 is warning that cases 2 and 3 already exist (reference to case 1)</p>

<p><strong>Thirt Question</strong>
Does <code>fpo</code> (file pointer to output-file) increment itself automatically by writig a char?</p>

<p><strong>Question four:</strong>
VS2015 is warning: </p>

<p>C4996   'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.</p>

<p>Is there another function I should use?</p>

<pre><code>int main()
{
    char c;
    FILE *fpi;
    FILE *fpo;
    fpi = fopen("texti.txt","r");
    fpo = fopen("texto.txt", "w");
    if (fpi == NULL)
        fprintf(stderr, "Fehler beim Lesen");
    while (!feof(fpi))
    {
        c = fgetc(fpi);
    switch (c)

{
    case 'ä'||'Ä':      
        fputc('a', fpo);
        fputc('e', fpo);
        break;

    case 'ö'||'Ö':
        fputc('o', fpo);
        fputc('e', fpo);
        break;

    case 'ü' || 'Ü':
        fputc('u', fpo);
        fputc('e', fpo);
        break;

    default:
        fputc((c), fpo);
    }
    fpi++;
}
fclose(fpi);
fclose(fpo);
</code></pre>

<p>}</p>
