Texas Instruments literature number SDLS128, a 546 KB PDF datasheet. The name does not reveal the device, so check the document heading for the covered 74-series part. TI's SDLS codes index its classic TTL logic datasheets. These documents typically hold pin diagrams, function tables, absolute maximum ratings and timing characteristics. Technicians use them to verify chip behavior or choose a replacement, after confirming that the marking on the board matches.
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 @datasheet_technar_org. 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.