Function comments (v1)

README.md

@@ -4,6 +4,12 @@
 
 First install the dependencies: `sudo apt install python3 xorriso make qemu-system`
 
+Also, you have to get an x86_64 toolchain for compilation. The easiest way to do that on most systems is to install it from Homebrew:
+
+```
+brew install x86_64-elf-gcc
+```
+
 Then, to compile the kernel and make an ISO image file: `make build-iso`
 To run it with QEMU, `make run`