RevMedia

Writing to a file with SI.MFS attached causes the ! code to be invoked. The ! code (being essentially a dictionary item) uses @ANS to pass information around - thus before returning control to the calling program, it nulls down @ANS. Hence the act of writing to a file with SI.MFS attached clears out @ANS. The moral is simple, as @ANS is a temporary answer variable, do not use it to store values between processes.