Synopsis Simply, in order to reduce the complexity of designing and building computers, nearly all the computers are made to execute relatively simple commands.  A programme for a computer must be built by combining very simple commands into a programme in what is called machine language.  Since this is a tedious and error-prone process, most of the programming is, instead, done using a high-level programming language.  This language can be different that the computer can execute; so some means for bridging the gap is required.  This is where the compiler comes in.

A compiler translates (or compiles) a programme, written in a high-level programming language that is suitable for human programmers into the low-level machine language that is required by computers.  A good compiler should, however, be able to get quite close to the speed of hand-written code, when translating well-structured programmes. Since, writing a compiler is a nontrivial task, it is a good idea to structure the work.  This book is meant to support a practically oriented course in compiler designing for teachers and students in Computer Science.