As mentioned in chapter 2, you can customize the default option settings through option files. These files are processed in the order that they are listed in the X390INI environment variable. You can create option files to customize the default option settings by group, project, user, branch of the source tree, or even by source file.
As an example, you could set the options as follows: Set default options for everyone in the txa.ini file. Set overrides to these defaults for each user group in the first file listed in the X390INI environment variable. Next, each individual user may have an optional file in their home directory containing customized default option settings in the second file listed. Then set the options common to the project in the third file listed and allow an optional file containing options specific to the source file in the fourth file. In Windows NT you might specify this as:
SET X390INI="&Xtxa.ini";F:\group\x390opts.ini;@%HOMEDRIVE%%HOMEPATH%\x390opts.ini;"&Dx390opts.ini";"@&D&F.ini"The at-sign ( @ ) in front of a file name allows the assembler to continue if the file does not exist. Only the options that are different from the preceding settings need to be in each file.
In addition to the optio files listed in the X390INI environment variable, option file lists may also be specified by the INCLUDE assembler option. Option files listed in the INCLUDE option are read when the INCLUDE option is processed. Since the INCLUDE option may be specified within an option file, this allows option files to be nested. Also, since the INCLUDE option may be specified on the command line, option files may be specified without the need to set the X390INI environment variable.