The 2SC4030 transistor is documented in this 119 KB PDF, which is listed in the schematic section. Its JIS prefix 2SC denotes an NPN bipolar transistor; no further detail such as manufacturer or case appears in the name. Expect ratings tables, characteristic curves and an outline drawing inside. Technicians use these to check whether a failed part can be swapped for another type and to avoid mixing up pins during installation. Verify that the component on the board carries the same number before relying on the sheet.
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.