///////   Program lowercase.C   /////// 
#include        <iostream.h>
#include        <fstream.h>
#include        <stdlib.h>
#include        <ctype.h>

char lower(char c)
{   if ( isupper(c) )
        return( tolower(c) );
    else return(c);
}

void doio(istream& in, ostream& out)
{   char c;
    while (in.get(c))
        out.put( lower(c) );
    out.flush();
}

int main (int argc,  char* argv[])
{   if ( argc == 1 )      // use standard I/O
        doio(cin, cout);
    else if ( argc == 3 ) // use files given
    {   fstream infile(argv[1], ios::in);
        if ( infile.fail() )
        {   cerr << argv[0] << ":can't open input file "
                 << argv[1] << "\n";
            exit(1);
        }
        fstream ofile(argv[2], ios::out);
        if ( ofile.fail() )
        {   cerr << argv[0] << ":can't open output file " 
                 << argv[2] << "\n";
            exit(1);
        }
        doio(infile, ofile);
    }
    else   // error
    {   cerr << "Usage: lower infile outfile \n";
        exit(1);
    }
    return(0);
}
///////   End of lowercase.C  ///////