Obtaining a C compiler to use

There are a lot of C compiler programs. The one prevalent in the linux world is gcc. One in the Microsoft world is bcc32. These compilers are command line programs, not graphical ones. You could get and install these, or might even already have them, on your local computer. Then, there are web sites where C compilers are available to be used.  You give them your source code, they compile and run it, and they give you the results (error messages from the compiler, or output of your program). It's equivalent to running the program yourself with your own tool, just they do the job for you over on their platform and tell you what happened.

bcc32 -  if you wish, on a Windows computer you can install the bcc32 compiler. From the link here download file "Compiler.zip" then unzip it. A folder named "Compiler" will result. It will contain a folder named "BCC compiler". Which in turn will contain a file named "Borland5.5setupInstructions.rtf". That file has some instruction for setting the compiler up on your Windows computer.

gcc - if you have access to a linux environment you will likely find gcc installed there. I don't generally recommend it to students because the text editors available in most linux environments are unfamiliar. Programming starts with a text editor, in which you compose code in the source language. Almost all students are able to edit with Notepad (prevalent in Windows), but almost none with vi (prevalent in linux).

online/website alternatives - there are computers on the internet that are web servers (i.e., your browser can talk to them) and also contain a C compiler they let you run. You submit your C program to their web server, which hands it off to their C compiler, and the results of their attempt to compile and run your program are fed back by the web server to your browser for you to see. This is the one of my choice:  https://www.onlinegdb.com/online_c_compiler
Here are 3 others, and there are probably more:
 https://repl.it/languages/C, https://rextester.com/l/c_online_compiler_gcc, https://www.jdoodle.com/c-online-compiler