eCos (Embedded Configurable OS) is a free open source real-time operating system under GPL License . The highly configurable nature of eCos allows the operating system to be customized to precise application requirements, delivering the best possible run-time performance and an optimized hardware resource footprint. In addition to real-time kernel transplantation and optimization for C-SKY CPU, eCos-3.0 for C-SKY also includes the following components: POSIX interface; ISO C function library, math library and C++ standard template library; supports MiniGUI graphics library; supports TCP/IP network protocol stack; supports various file systems; supports driver framework with hardware abstract layer and implements general hardware driver, such as UART, SPI, IIC, FrameBuffer, WDT and Ethernet; supports GDB directly debugging.