PDF document of 126 KB for a part labelled 23c256. The 23C prefix is typically used for mask-programmed ROMs, with the number pointing to a 256 Kbit size, although the name alone does not state the maker. Expect pin assignments, memory organisation, access timing and electrical limits inside. It is handy when identifying a ROM on vintage or embedded hardware, checking its supply and control pins, or finding a compatible EPROM for substitution. Confirm the actual chip marking matches before relying on the pinout.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.