Tera Term is a free software terminal emulator for Windows, supporting SSH, Telnet, serial port connections, and file transfer protocols (XMODEM, YMODEM, ZMODEM, Kermit, B-Plus, Quick-VAN). It includes a macro scripting language (TTL) for automation, a plugin system (TTX) for extensibility, and integration with Cygwin/MSYS2/Git Bash. The architecture is a Windows-native desktop application with multiple DLL components: the main terminal emulator (ttermpro.exe), SSH client (ttxssh.dll), proxy support (ttproxy.dll), macro engine (ttpmacro.exe), and various utility libraries. Key entry points include the main window creation in teraterm.cpp, the plugin loading in ttplug.cpp, and the macro interpreter in ttmmain.cpp. External dependencies include OpenSSL/LibreSSL for cryptography, zlib for compression, Oniguruma for regex, and Argon2 for password hashing. The codebase is extensive and long-lived, with compatibility layers for older Windows versions and multiple build systems (CMake, Visual Studio, MinGW).