*.e00 files are in ArcInfo Interchange Format

From the Importing an ArcInfo interchange file (E00) help page:

The ArcInfo interchange file format, also known as an export file (.e00), is used to enable a coverage, grid or TIN, and associated INFO tables to be transferred between different machines that are not connected by any type of file sharing network. ArcInfo interchange files have an .e00 extension, which increases incrementally to .e01, .e02, and so on, if the interchange file is composed of several separate files.