The 2SC5777 is covered by this small 29.9 KB PDF, catalogued as a schematic but most likely a single-part datasheet. In JIS semiconductor naming, 2SC denotes an NPN bipolar transistor. Nothing else is stated in the name, so package style, maker and electrical limits must be taken from the document. The usual use is to check the pin order and absolute maximum ratings when replacing a failed transistor or hunting for a substitute. Confirm the body marking on the board matches 2SC5777, since short markings can be ambiguous.
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.