CS 145, like CS 135 and CS 115, uses the latest release of DrRacket (for Fall 2020, 7.8), which can be downloaded here. It is installed in the Mac labs on the 3rd floor of MC and on the Linux servers in the CS Undergraduate Environment, but it is by far easiest to use it on your own computer.
If you plan on taking CS 146, you will probably need to download and get used to some other software before that course begins. Later in CS 145, we will be encouraging you to do this before the end of this year so as to avoid problems in January, and we may possibly use the new software briefly near the end of the fall term. There are several possibilities for completing work that does not involve DrRacket:
Use of native Windows software (compilers, IDEs, etc.) has caused problems for students in the past and we do not recommend it.
CS 146 may necessitate the use of an external text editor, and knowledge of one will be useful in later CS courses. We recommend using Pico, Nano, Vim, or Emacs. Handouts on Cygwin and other tools will be posted later.