This book is intended to provide comprehensive information about low-level programming in the assembler language for a wide range of computer systems, including:

• embedded systems - constrained devices,
• mobile and mobile-like devices - based on ARM architecture,
• PCs and servers - based on Intel and AMD x86 and in particular 64-bit (x86_64) architecture.

The book also contains an introductory chapter on general computer architectures and their components.

While low-level assembler programming was once considered outdated, it is now back, and this is because of the need for efficient and compact code to save energy and resources, thus promoting a green approach to programming. It is also essential for cutting-edge algorithms that require high performance while using constrained resources. Assembler is a base for all other programming languages and hardware platforms, and so is needed when developing new hardware, compilers and tools. It is crucial, in particular, in the context of the announced switch from chip manufacturing in Asia towards EU-based technologies.

We (the Authors) assume that persons willing to study this content possess some general knowledge about IT technologies, e.g., understand what an embedded system is and the essential components of computer systems, such as RAM, CPU, DMA, I/O, and interrupts and knows the general concept of software development with programming languages, C/C++ best (but not obligatory).