Assembly Language and Computer Organization - Wikibooks, open books for an open worldPublished by Addison-Wesley Longman, Incorporated. Seller Rating:. Condition: Good. A copy that has been read, but remains in clean condition. All pages are intact, and the cover is intact. The spine may show signs of wear.
Machine Instructions 1: Instruction Operands
An assembly language or assembler language ,  often abbreviated asm , is any low-level programming language in which there is a very strong correspondence between the instructions in the language and the architecture's machine code instructions. Assembly code is converted into executable machine code by a utility program referred to as an assembler. The conversion process is referred to as assembly , as in assembling the source code. Assembly language usually has one statement per machine instruction , but comments and statements that are assembler directives ,  macros ,   and symbolic labels of program and memory locations are often also supported. Each assembly language is specific to a particular computer architecture and sometimes to an operating system. In contrast to assembly languages, most high-level programming languages are generally portable across multiple architectures but require interpreting or compiling , a much more complicated task than assembling.
Stated simply, this book is about how computers work. In the first part of the book, we will explore computer behavior by means of writing computer programs. Unlike most programmers, we will be writing programs for computers at their most basic level. We will be commanding them directly in assembly code and machine language with the aim of seeing what is going on "under the hood. Even though the art of writing these kind of programs is becoming rarer, learning assembly language is still a worthy pursuit as it reveals what is going on inside the machine and teaches programmers to "think like a computer. In later chapters we will be looking at other architectures and instruction sets.
In order to explore how computers operate, we must first arrive at an explanation of what computers actually do. No doubt, you have some idea of what computers are capable of. After all, odds are high that you are reading this on a computer right now! If we tried to list all the functions of computers, we would come up with a staggeringly complex array of functions and features. Instead, what we need to do is peal back all the layers of functionality and see what's going on in the background. If we look at a computer at its most abstract level, what they do is process information. We could represent this sort of abstract machine as some sort of memory and some sort of processor.