1.3: Why Learn Assembly Language

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The goal of this text is to provide a comprehensive introduction to programming in assembly language. The reasons for learning assembly language are more about understanding how a computer works instead of developing large programs. Since assembly language is machine specific, the lack of portability is very limiting for programming projects.

The process of actually learning assembly language involves writing non-trivial programs to perform specific low-level actions including arithmetic operations, function calls, using stack-dynamic local variables, and operating system interaction for activities such as input/output. Just looking at small assembly language programs will not be enough.

In the long run, learning the underlying principles, including assembly language, is what makes the difference between a coding technician unable to cope with changing languages and a computer scientist who is able to adapt to the ever-changing technologies.

The following sections provide some detail on the various, more specific reasons for learning assembly language.

Better Understanding of Architecture Issues

Learning and spending some time working at the assembly language level provides a richer understanding of the underlying computer architecture. This includes the basic instruction set, processor registers, memory addressing, hardware interfacing, and Input/ Output. Since ultimately all programs execute at this level, knowing the capabilities of assembly language provides useful insights into what is possible, what is easy, and what might be more difficult or slower.

Understanding the Tool Chain

The tool chain is the name for the process of taking code written by a human and converting it into something that the computer can directly execute. This includes the compiler, or assembler in our case, the linker, the loader, and the debugger. In reference to compiling, beginning programmers are told “just do this” with little explanation of the complexity involved in the process. Working at the low-level can help provide the basis for understanding and appreciating the details of the tool chain.

Improve Algorithm Development Skills

Working with assembly language and writing low-level programs helps programmers improve algorithm development skills by practicing with a language that requires more thought and more attention to detail. In the highly unlikely event that a program does not work the first time, debugging assembly language also provides practice debugging and requires a more nuanced approach since just adding a bunch of output statements is more difficult at the assembly language level. This typically involves a more comprehensive use of a debugger which is a useful skill for any programmer.

Improve Understanding of Functions/Procedures

Working with assembly language provides a greatly improved understanding of how function/procedure calls work. This includes the contents and structure of the function call frame, also referred to as the activation record. Depending on the specific instance, the activation record might include stack-based arguments, preserved registers, and/or stack dynamic local variables. There are some significant implementation and security implications regarding stack dynamic local variables that are best understood working at a low-level. Due to the security implications, it would be appropriate to remind readers to always use their powers for good. Additionally, use of the stack and the associated call frame is the basis for recursion and understanding the fairly straightforward implementation of recursive functions.

Understanding of I/O Buffering

In a high-level language, input/output instructions and the associated buffering operations can appear magical. Working at the assembly language level and performing some low-level input/output operations provides a more detailed understanding of how input/output and buffering really works. This includes the differences between interactive input/output, file input/output, and the associated operating system services.

Understand Compiler Scope

Programming with assembly language, after having already learned a high-level language, helps ensure programmers understand the scope and capabilities of a compiler. Specifically, this means learning what the compiler does and does not do in relation to the computer architecture.

Introduction Multi-processing Concepts

This text will also provide a brief introduction to multi-processing concepts. The general concepts of distributed and multi-core programming are presented with the focus being placed on shared memory, threaded processing. It is the author’s belief that truly understanding the subtle issues associated with threading such as shared memory and race conditions is most easily understood at the low-level.

Introduction Interrupt Processing Concepts

The underlying fundamental mechanism in which modern multi-user computers work is based on interrupts. Working at a low-level is the best place to provide an introduction to the basic concepts associated with interrupt handling, interrupt service handles, and vector interrupts.