# Simulate a regular Turing Machine with one that cannot write blanks

Consider a Turing machine that cannot write blanks. How does one show that such a machine can simulate a standard Turing machine?

To simulate a Turing machine $M$ that can write blanks with a Turing machine $M'$ that can't, just give $M'$ an extra character in its alphabet. Whenever $M$ writes a blank, $M'$ writes this new character and, whenever $M'$ sees the blank or the new character, it does what $M$ would do if it saw the blank.