Assembly Computer language

This is a brief introduction to assembly language. Assembly language is the most basic programming language available for any processor. With assembly language, a programmer works only with operations implemented directly on the physical CPU. Assembly language lacks high-level conveniences such as variables and functions, and it is not portable between various families of processors. Nevertheless, assembly language is the most powerful computer programming language available, and it gives programmers the insight required to write effective code in high-level languages. Learning assembly language is well worth the time and effort of every serious programmer.

The Basics

Before we can explore the process of writing computer programs, we have to go back to the basics and learn exactly what a computer is and how it works. Every computer, no matter how simple or complex, has at its heart exactly two things: a CPU and some memory. Together, these two things are what make it possible for your computer to run programs.

On the most basic level, a computer program is nothing more than a collection of numbers stored in memory. Different numbers tell the CPU to do different things. The CPU reads the numbers one at a time, decodes them, and does what the numbers say. For example, if the CPU reads the number 64 as part of a program, it will add 1 to the number stored in a special location called AX. If the CPU reads the number 146, it will swap the number stored in AX with the number stored in another location called BX. By combining many simple operations such these into a program, a programmer can make the computer perform many incredible things.

As an example, here are the numbers of a simple computer program: 184, 0, 184, 142, 216, 198, 6, 158, 15, 36, 205, 32. If you were to enter these numbers into your computer's memory and run them under MS-DOS, you would see a dollar sign placed in the lower right hand corner of your screen, since that is what these numbers tell the computer to do.

Assembly Language

Although the numbers of the above program make perfect sense to a computer, they are about as clear as mud to a human. Who would have guessed that they put a dollar sign on the screen? Clearly, entering numbers by hand is a lousy way to write a program.

It doesn't have to be this way, though. A long time ago, someone came up with the idea that computer programs could be written using words instead of numbers. A special program called an assembler would then take the programmer's words and convert them to numbers that the computer could understand. This new method, called writing a program in assembly language, saved programmers thousands of hours, since they no longer had to look up hard-to-remember numbers in the backs of programming books, but could use simple words instead.