Before running the **clang** command, install the LLVM compiler. For details, see [Installing LLVM](../quick-start/quickstart-lite-steps-hi3861-setting.md).
**--target=arm-liteos**: specifies the compilation platform, which is arm-liteos.
**--sysroot=$\{YOUR\_ROOT\_PATH\}/prebuilts/lite/sysroot**: specifies the directory in which you can search for the header file and the dependent standard libraries.
**--sysroot=$\{YOUR\_ROOT\_OUT\_PATH\}/sysroot**: specifies the directory in which you can search for the header file and the dependent standard libraries.
A user-mode program can be started in either of the following ways: