W 0 Please type some input characters, then press escape.
char: W 1
esc: I 27 the escape character
one: I 1
bell: I 7 the noise character
main: INP opsys
   STA char
   XOR esc
   BZE opsys
   LDA char
   ADD one
   OUT opsys
   LDA bell
   OUT opsys
   BUN main