https://people.inf.ethz.ch/wirth/CompilerConstruction/index.html by Niklaus Wirth

• CompilerConstruction1.pdf
• CompilerConstruction2.pdf
• Source code

I have no doubt that this is the best book if I want to learn about compilers. The author has a proven record of simplicity and beautifully designed code.

Related to

• Oberon.ARM.Compiler.pdf
• The Oberon programming language by Niklaus Wirth
• Project Oberon (New Edition 2013) by Niklaus Wirth
• Algorithms and Data Structure - Niklaus Writh - 2012.pdf
• Nils M Holm