#### Answer

\begin{array}{l}{\text { The HALT op code is } 1111 . \text { HALT does not require an address but }} \\ {\text { something has to be put into those } 12 \text { bits. Typically, an assembler }} \\ {\text { will set all the bits to } 0 \text { , although it does not really matter. Assuming }} \\ {\text { we put zeroes into the address field we will end up with: }} \\ {\qquad 1111000000000000}\end{array}