This is a faithful-ish emulation of an IBM i (formerly AS/400) 5250 green-screen session.
Sign on with any user / password to enter. From the Main Menu you can navigate menus, type IBM i commands at the command line, or use option numbers.
Try these commands:
WRKLIBPDM — work with libraries
WRKOBJPDM PURPLE — work with objects in library
WRKMBRPDM PURPLE/QRPGLESRC — members in source file
STRSEU PURPLE/QRPGLESRC HELLO — edit a member
DSPLIBL — display library list
WRKACTJOB — work with active jobs
CALL HELLO — run a program
SIGNOFF — sign off
From any list, type an option number (2=Edit, 5=Display, 12=Work-with, etc.) next to a row and press Enter.
Function keys: F3 exit · F4 prompt · F5 refresh · F6 create · F9 retrieve last command · F12 cancel/back