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Chapter Two Hello, World of Assembly Language

2.1 Chapter Overview

This chapter is a "quick-start" chapter that lets you start writing basic assembly language programs right away. This chapter presents the basic syntax of an HLA (High Level Assembly) program, introduces you to the Intel CPU architecture, provides a handful of data declarations and machine instructions, describes some utility routines you can call in the HLA Standard Library, and then shows you how to write some simple assembly language programs. By the conclusion of this chapter, you should understand the basic syntax of an HLA program and be prepared to start learning new language features in subsequent chapters.

2.2 Installing the HLA Distribution Package

Before you can learn assembly language programming using HLA, you must first successfully install HLA on your system. Currently, HLA is available for the Linux and Windows operating systems. This section explains how to install HLA on these two systems. If HLA is already running on your system, you may skip to the next major section in this chapter.

The latest version of HLA is available from the Webster web server at

http://webster.cs.ucr.edu

Go to this web site and following the HLA links to the "HLA Download" page. From here you should select the latest version of HLA for download to your computer. The HLA distribution is provided in a "Zip File" compressed format. Under Windows, you will need a decompressor program like PKUNZIP or WinZip in order to extract the HLA files from this zipped archive file; under Linux, you will use the GZIP and TAR programs to decompress and extract HLA. A detailed description of the use of these decompression products is beyond the scope of this manual, please consult the software vendor's documentation or their web page for information concerning the use of these products; this discussion will only briefly describe how to use them to extract important HLA files.

This text assumes that you will unzip the HLA distribution into the root directory of your C: drive under Windows, or to the "/usr/hla" directory under Linux. You can certainly install HLA anywhere you want, but you will have to adjust the following descriptions if you install HLA somewhere else. If possible, you should install HLA using root/administrator priviledges; regardless, you should make sure the permissions are set properly on the files so everyone has read and execute access to the HLA files; if you are unsure how to do this, please consult your operating system's documentation or consult a system administrator.

HLA is a console application. In order to run the HLA compiler you must run the command window program (this is "command.com" on Windows 95 and 98, or "cmd.exe" on Windows NT and Windows 2000; Linux users typically run "bash" or some other shell). This also means that you should be familiar with some simple "command line interface" (CLI) or "shell" commands.

Most Windows distributions let you run the command prompt windows from the Start menu or from a submenu hanging off the start menu (you may also select "RUN" from the Start menu and type "cmd" as the program name). This text assumes that you are familiar with the Windows command window and you know how to use some basic command window commands (e.g., dir, del, rename, etc.). If you have never before used the Windows command line interpreter, you should consult an appropriate text to learn a few basic commands.

Most Linux distributions run "bash" or some other shell program whenever you open up a terminal window (e.g., a GNOME or KDE terminal window or an X-TERM window). There are some minor differences between the shells running under Linux, this document assumes that you are using GNU's "bash" shell. Again, this text assumes that you are comfortable with a few commands like ls, rm, and mv. If you have never used a Unix shell program before, you should consult an appropriate text or the on-line documentation to learn a few basic commands.

Before you can actually run the HLA compiler, you must set the system execution path and set up various environment variables. The following subsections explain how to do this under Windows and then Linux.

2.2.1 Installation Under Windows

HLA is not a stand alone program. It is a compiler that translates HLA source code into a lower-level assembly language. A separate assembler, such as MASM, then completes the processing of this low-level intermediate code to produce an object code file. Finally, you must link the object code output from the assembler using a linker program. Typically you will link the object code produced by one or more HLA source files with the HLA Standard Library (hlalib.lib) and, possibly, several operating system specific library files (e.g., kernel32.lib under Windows). Most of this activity takes place transparently whenever you ask HLA to compile your HLA source file(s). However, for the whole process to run smoothly, you must have installed HLA and all the support files correctly. This section will discuss how to set up HLA on your Windows system.

First, you will need an HLA distribution for Windows. The latest version of HLA is always available on Webster at http://webster.cs.ucr.edu. You should go there and download the latest version if you do not already possess it.

As noted earlier, HLA is not a stand alone assembler. The HLA package contains the HLA compiler, the HLA Standard Library, and a set of include files for the HLA Standard Library. If you write an HLA program with just this code, HLA will produce an "ASM" file and then stop. To produce an executable file you will need Microsoft's MASM and LINK programs, along with some Windows library files, to complete the process. The easiest way to get all the files you need is to download the "MASM32" package from http://www.pdq.com.au/home/hutch/masm.htm or any of the other places on the net where you can find the MASM32 package (Webster maintains a current link if this link is dead). Once you unzip this file, it's easy to install the MASM32 package using the install program it supplies. You must install MASM32 (or MASM/LINK/Win32 library files) before HLA will function properly.

Here are the steps I went through to install MASM32 on my system: 


 
path=c:\hla;c:\masm32\bin;%path%
 
set lib=c:\masm32\lib;c:\hla\hlalib;%lib%
 
set include=c:\hla\include;c:\masm32\include;%include%
 
set hlainc=c:\hla\include
 
set hlalib=c:\hla\hlalib\hlalib.lib
 

 


 
program HelloWorld;
 
#include( "stdlib.hhf" )
 
begin HelloWorld;
 

 
	stdout.put( "Hello, World of Assembly Language", nl );
 

 
end HelloWorld;
 

 


 
HLA (High Level Assembler)
 
Written by Randall Hyde and released to the public domain.
 
Version Version 1.32 build 4904 (prototype)
 

 
Files:
 
1: hw.hla
 

 
Compiling "hw.hla" to "hw.asm"
 

 
Assembling hw.asm via "ml /c /coff /Cp  hw.asm"
 

 
Microsoft (R) Macro Assembler Version 6.14.8444
 
Copyright (C) Microsoft Corp 1981-1997. All rights reserved.
 

 
 Assembling: hw.asm
 
Linking via "link -subsystem:console  /heap:0x1000000,0x1000000 
/stack:0x1000000,0x1000000 /BASE:0x3000000 /machine:IX86  -entry:?HLAMain @hw.link  
-out:hw.exe kernel32.lib user32.lib  c:\hla\hlalib\hlalib.lib hw.obj"
 
Microsoft (R) Incremental Linker Version 5.12.8078
 
Copyright (C) Microsoft Corp 1992-1998. All rights reserved.
 

 
/section:.text,ER 
 
/section:readonly,R 
 
/section:.edata,R 
 
/section:.data,RW 
 
/section:.bss,RW 
 

 


 
		HW

1) Open System Properties (Winkey-Break is a convenient shortcut) and go to Advanced tab, then Environment Variables. Add "c:\hla" to the Path in SYSTEM VARIABLES, not in "User variables for <your win2k login name>". Click OK, but keep the Environment Variables window open, we're not done.
2) Look at the contents of ihla.bat (ABOVE):
3) In "User Variables for <your login name>", you must end up with each of these settings. For example, to create hlainc, you click the "New..." button, type "hlainc" as the name of the variable, and type "c:\hla\include" as the Variable value (all without quotes of course). If there is already a path set, and it already has some value, add this immediately to the end: ";c:\hla;%path%" and that will preserve your existing User and System paths as well as adding c:\hla.
For example, suppose you opened up your User Variables for <login name> and it already said "C:\Private
Files\PantiePix;c:\winnt\system32;c:\winnt;c:\winnt\System32\Wbem;d:\lcc\bin;D:\PROGRA~1\ULTRAE~1;D:\4NT300;C:\msoffice\Office;c:/hla",
you would click on Edit and type "C:\Private Files\PantiePix;c:\hla;%path%"
(Same advice for preserving existing lib and include settings)
4) Once you reboot the computer, you should be all set for "Hello world of assembly language"! (without having to run the IHLA.BAT file.)

Installing HLA is a complex and slightly involved process. Unfortunately, this is necessary because I don't have the rights to distribute MASM, LINK, and other Microsoft files. Fortunately, HUTCH has collected all of these files together so they are easy to download. If you are concerned about possible legal issues with the download, you may legally download MASM and LINK from Microsoft's site. A link on Webster (at the URL above) describes how to do this. At the time this was being written, work was progressing on HLA to produce TASM compatible output and plans were in the works to produce NASM and Gas versions as well. However, you will still have to obtain the Microsoft library files from some source if you intend to produce a Win32 application. Versions of HLA may appear for other Operating Systems as well. Check out Webster to see if any progress has been made in this direction.

The most common two problems people have running HLA involve the location of the Win32 library files and the choice of linker. During the linking phase, HLA (well, link.exe actually) requires the kernel32.lib, user32.lib, and gdi32.lib library files. These must be present in the pathname(s) specified by the LIB environment variable. If, during the linker phase, HLA complains about missing object modules, make sure that the LIB path specifies the directory containing these files. If you're a MS VC++ user, installation of VC++ should have set up the LIB path for you. If not, then locate these files (they are part of the MASM32 distribution) and copy them to the HLA\HLALIB directory (note that the ihla.bat file includes c:\hla\hlalib as part of the LIB path).

Another common problem with running HLA is the use of the wrong link.exe program. Microsoft has distributed several different versions of link.exe; in particular, there are 16-bit linkers and 32-bit linkers. You must use a 32-bit segmented linker with HLA. If you get complaints about "stack size exceeded" or other errors during the linker phase, this is a good indication that you're using a 16-bit version of the linker. Obtain and use a 32-bit version and things will work. Don't forget that the 32-bit linker must appear in the execution path (specified by the PATH environment variable) before the 16-bit linker.

2.2.2 Installation Under Linux

HLA is not a stand alone program. It is a compiler that translates HLA source code into a lower-level assembly language. A separate assembler, such as Gas (as), then completes the processing of this low-level intermediate code to produce an object code file. Finally, you must link the object code output from the assembler using a linker program. Typically you will link the object code produced by one or more HLA source files with the HLA Standard Library (hlalib.a). Most of this activity takes place transparently whenever you ask HLA to compile your HLA source file(s). However, for the whole process to run smoothly, you must have installed HLA and all the support files correctly. This section will discuss how to set up HLA on your system.

First, you will need an HLA distribution for Linux. The latest version of HLA is always available on Webster at http://webster.cs.ucr.edu. You should go there and download the latest version if you do not already possess it.

As noted earlier, HLA is not a stand alone assembler. The HLA package contains the HLA compiler, the HLA Standard Library, and a set of include files for the HLA Standard Library. If you write an HLA program with just this code, HLA will produce an "ASM" file and then stop. To produce an executable file you will need GNU's as and ld programs (these come with any Linux distribution that supports compiling C/C++ programs). Note that HLA only works with Gas v2.10 or later. The Gas assembler is part of the Binutils package. If you don't have version 2.10 or later, download an appropriate binutils package from the internet. HLA will generate errors when it attempts to assemble its output via an invocation of the as (Gas) executable if you don't have Gas v2.10 or later installed in your system.

Here are the steps I went through to install HLA on my Linux system: 


 
program HelloWorld;
 
#include( "stdlib.hhf" )
 
begin HelloWorld;
 

 
	stdout.put( "Hello, World of Assembly Language", nl );
 

 
end HelloWorld;
 

 


 
HLA (High Level Assembler) Parser
 
Written by Randall Hyde and released to the public domain.
 
Version Version 1.39 build 6845 (prototype)
 
-t active
 
File: t.hla
 

 
Compiling "t.hla" to "t.asm"
 
HLA (High Level Assembler)
 
Copyright 1999, by Randall Hyde, all rights reserved.
 
Version Version 1.39 build 6845 (prototype)
 
ELF output
 
Using GAS assembler
 
GAS output
 
-test active
 

 
Files:
 
1: t.hla
 

 
Compiling 't.hla' to 't.asm'
 
using command line [hlaparse  -v -sg -test "t.hla"]
 

 
Assembling "t.asm" via [as -o t.o  "t.asm"]
 
Linking via [ld   -o "t"  "t.o" "/usr/hla/hlalib/hlalib.a"]

Installing HLA is a complex and slightly involved process; though take heart, it's a lot simpler to install HLA under Linux than Windows! (See the previous section if you need proof.) Versions of HLA may appear for other operating systems (beyond Windows and Linux) as well. Check out Webster to see if any progress has been made in this direction. Note a very unique thing about HLA: Carefully written (console) applications will compile and run on all supported operating systems without change. This is unheard of for assembly language! So if you are using multiple operating systems supported by HLA, you'll probably want to download files for all supported OSes.

Note: to run the HelloWorld program, a Linux user would type "hw" (or possibly "./hw") at the command line prompt.

2.2.3 Installing "Art of Assembly" Related Files

Although HLA is relatively flexible about where you put it on your system, this text assumes you've installed HLA in the "hla" directory on your C: drive under a Win32 operating system or in "/usr/hla" under Linux. This text also assumes the standard directory placement for the HLA files, which has the following layout

The "Art of Assembly" (AoA) software distribution has the following directory tree structure:

The main HLA directory contains the executable code for the compiler. This consists of two files, HLA.EXE/hla and HLAPARSE.EXE/hlaparse (Windows/Linux). These two programs must be in the current execution path in order to run the compiler. Under Windows, it wouldn't hurt to put the ml.exe, ml.err, link.exe, mspdbX0.dll (x=5, 6, or greater), and msvcrt.dll files in this directory as well. Under Linux, the "as" and "ld" programs are already in the execution path, assuming your Linux system supports C/C++ development.

The Doc directory contains reference material for HLA in PDF and HTML formats. If you have a copy of Adobe Acrobat Reader, you will probably want to read the PDF versions since they are much nicer than the HTML versions. These documents contain the most up-to-date information about the HLA language; you should consult them if you have a question about the HLA language or the HLA Standard Library. Generally, material in this documentation supersedes information appearing in this text since the HLA document is electronic and is probably more up to date.

The Examples directory contains a large set of HLA programs that demonstrate various features in the HLA language. If you have a question about an HLA feature, you can probably find an example program that demonstrates that feature in the Examples directory. Such examples provide invaluable insight that is often superior to a written description of the feature. Note that some of these programs may be specific to Windows or Linux, not all will compile and run under either operating system.

The hlalib directory contains the object code for the HLA Standard Library. As you become more competent with HLA, you may want to take a look at how HLA implements various library functions by checking out the library source code in the hlalibsrc subdirectory.

The include directory contains the HLA Standard Library include files. These special files (that end with a ".hhf" suffix, for "HLA Header File") are needed during assembly to provide prototype and other information to your program. The example programs in this chapter all include the HLA header file "stdlib.hhf" that, in turn, includes all the other HLA header files in the standard library.

The Tests directory contains various test files that test the correct operation of the HLA system. HLA includes these files as part of the distribution package because they provide additional examples of HLA coding.

The AoA directory contains the code specific to this textbook. This directory contains all the source code to the (complete) programs appearing in this text. It also contains the programs appearing in the Laboratory Exercises section of each chapter. Therefore, this directory is very important to you. Within this subdirectory, the information is further divided up by volume and chapter. The material for Chapter One appears in the "ch01" subdirectory of the "volume1" directory in the AoA directory tree, the material for Chapter Two appears in the "ch02" subdirectory of the "volume1" directory, etc..

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