Posters

Your posters should primarily be targeted at someone who knows Hack but does not understand how the VM II system works.

The major topics discussed in this chapter are:

• Easy: label, goto, if-goto. Posters for these topics need to clarify details and work on an extension of some kind.
• Function
• Call
• Return
• Control flow for a call

Notes

Saving the return address and jumping back to it is not what anyone expects. The most common confusion is “pushing a label on the stack” (vs an actual number).

Also look for the confusion of ROM addresses (lines in the program) with RAM addresses (memory locations that create the stack).

Another common issue is a group understanding the topic well but communicating it poorly. Posters should contain details that will help someone who is lost.

Evaluation criteria:

• Clarity
• Use of space
• Challenge (if applicable)

Enhancements to if-goto

Two-way jump: if-goto THEN-LABEL ELSE-LABEL. Push the “next address” onto the stack so both labels can jump to the end when they are done. Having these “mini-subroutines” does automate a feature that probably ends up needing to be done by hand.

This is the end.