For this class, you will need to use the LC-3 simulator for your programming assignments. Since there are only two versions of the simulator, a Windows version and a Linux version, it may be challenging to complete the programs if you own a Mac.
Even if you do own a Mac, there are many options available to you. Using software such as VM Ware, Parallels, or Boot Camp, you could install Windows 7 on your Mac and proceed to use the Windows LC-3 simulator.
Acquiring a copy of Windows can be expensive, but the Engineering Department's IT Group offers a special deal with the Microsoft Developers Network Academic Alliance (MSDN AA) which allows you to download certain Microsoft software (including Windows 7) for free if used for academic purposes.
Alternatively, the ECE Department's IT services offers a "Virtual" computer lab which you can remotely access from your Mac (or Windows machine). When you access one of these Remote Desktops using your UT EID, any information you save will be permanently stored on the Remote Desktop and only accessible to you.
Even if you do not own a Mac, the information on this page, especially the MSDN AA instructions, is likely to be useful to you.