### A good answer might be:

It is a machine language program in memory (possibly in ROM).

# Starting SPIM

On SPIM, the trap handler is a machine language program that is optionally loaded into SPIM memory. On a real machine a trap handler might be permanently in ROM, might be loaded from a "boot sector" of the hard disk, or (in the good old days) might be entered into memory by hand.

To use the trap handler with SPIM ask for it in the Simulator Settings panel. Set the options "Allow pseudoinstructions" and "Load trap file" as well as the other options shown at right.

Now to assemble and load your program go to File Open and select the source file (just as we have been doing). Your program is loaded along with some initialization code. The initialization code starts at address 0x00400000, the address that has until now been where your programs started.

To run the program click on Simulator Go and then OK in the pop-up panel.

### QUESTION 6:

Can you single step starting at address 0x00400000 as before?