A simple time machine in C++

timemachine.cpp

#include <cstdio>
#include <cstdlib>
#include <unistd.h>

using namespace std;

int main( int argc, char *argv[] ) {
    int year;
    int now;
    char c;
    FILE* fi;
    FILE* fo;

    if ( argc != 2 ) {
        printf( "Usage: timemachine <year>\n" );
        return 1;
    }

    year = atoi( argv[ 1 ] );
    fi = fopen( "year.txt", "r" );
    fscanf( fi, "%i", &now );
    fclose( fi );

    if ( year > now ) {
        printf( "This time machine doesn't yet support going to the future. Sorry.\n" );
        return 1;
    }
    else if ( year == now ) {
        printf( "You are already in %i.\n", year );
        return 1;
    }
    else if ( year < 1900 ) {
        printf( "For security reasons, you cannot go back beyond 1900.\n" );
        return 1;
    }
    printf( "Warning: This program did not yet exist in %i. You may not be able to travel back.\n", year );
    printf( "Are you sure you want to continue? (Y/N) " );
    scanf( "%c", &c );

    if ( c != 'y' && c != 'Y' ) {
        printf( "Operation aborted.\n" );
        return 1;
    }

    printf( "Taking you back to year %i...\nThis may take a few moments.\n", year );

    sleep( 5 ); // TODO

    fo = fopen( "year.txt", "w" );
    fprintf( fo, "%i\n", year );
    fclose( fo );

    printf( "You are now in year %i.\n", year );

    return 0;
}