MASMTidy tidies MASM *.asm assembler source, aligning it in four columns. It also converts all your operators to lower case. It does not reorder the code in any way or insert or remove anything. It handles single line comments, tail comments and comment | style comments. To convert a single program, type: java.exe -jar C:\com\mindprod\masmtidy\masmtidy.jar myprogram.asm The results replace the old file, so you had better make a backup just in case this is not what you want. You can also list several files on the command line: java.exe -jar C:\com\mindprod\masmtidy\masmtidy.jar myprogram.asm C:\mydir\another.asm To use convert the current directory of asm files: java.exe -jar C:\com\mindprod\masmtidy\masmtidy.jar . Sorry no wildcards, or negative wildcards, just . , and .. DON'T USE WILDCARDS unless you deeply understand how they work. Read up on how they work in the Java glossary on the host site. Windows expands them, not MASMTidy, and feeds them to MASMTidy (or any other program) as a giant list of all the directories and files in the current directory. MASMTidy will thus tend process all the files in your directories, when you just meant to process the files in the current directory. The -s switch makes all subsequent directories searched recursively to include all their subdirectories. e.g. java.exe -jar C:\com\mindprod\masmtidy\masmtidy.jar -s E:\com will fix all *.asm files in the E:\com directory tree, ignoring other types of files. The -q option switch suppresses output. Without it, you see a list of the files it changed. If you have the jar extension set up as executable, you can abbreviate: C:\com\mindprod\masmtidy\masmtidy.jar . CONFIGURING You can change the column widths and suppress conversion of operators to lower case by modifying the constants in MASMSTate.java and recompiliing.