Building Different File Viewer
C, C++, Perl, VB, C#, VB.NET, JAVA, Delphi... basically you name it, it can do it. What language do you know the best? Use that if you can.
Also, don't write them by hand. You could either write a "generic" file viewer that uses a configuration file to describe the file to be viewed/edited or generate specific file viewers from configuration files that describe the file. If you're going to generate the code I'd recommend using xml for the config files as you can then use xslt for the generation. If you're going to produce a generic viewer then the format of the config file is up to you (I'd probably still use xml as you don't have to write a config file parser then).
A decently featured hex-editor type program should already have all the features you need. You shouldn't have to write anything.
Sounds like strange requirements. And you don't tell us about the environment.
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