When I compile and run code from http://www.learntosolveit.com/cprogramming/rot13.html and have a file alpha as

a
b
c

cat alpha | ./a.out gives

n
o
p

However, I wrote a code doing the same rotation as

#include <stdio.h>

int main()
{

    char ch;
    ch = getchar();

    if ('a' <= ch && ch <= 'm'){
        putchar(ch+13);}
    else if ('A' <= ch && ch <= 'M'){
        putchar(ch+13);}
    else if ('n' <= ch && ch <= 'z'){
        putchar(ch-13);}
    else if ('N' <= ch && ch <= 'Z'){
        putchar(ch-13);}
    return(0);
}

then cat alpha | ./a.out gives

nop

I thought in order to add newline, we also have to put putchar(‘\n’). Why is the behavior different? Thanks