1e41f4b71Sopenharmony_ci# telephony_data.h 2e41f4b71Sopenharmony_ci 3e41f4b71Sopenharmony_ci 4e41f4b71Sopenharmony_ci## Overview 5e41f4b71Sopenharmony_ci 6e41f4b71Sopenharmony_ciDefines C APIs for cellular data module. 7e41f4b71Sopenharmony_ci 8e41f4b71Sopenharmony_ci**Library**: libtelephony_data.so 9e41f4b71Sopenharmony_ci 10e41f4b71Sopenharmony_ci**System capability**: SystemCapability.Telephony.CellularData 11e41f4b71Sopenharmony_ci 12e41f4b71Sopenharmony_ci**Since**: 13 13e41f4b71Sopenharmony_ci 14e41f4b71Sopenharmony_ci**Related module**: [Telephony Data](ndk-apis-telephony-data.md) 15e41f4b71Sopenharmony_ci 16e41f4b71Sopenharmony_ci 17e41f4b71Sopenharmony_ci## Summary 18e41f4b71Sopenharmony_ci 19e41f4b71Sopenharmony_ci 20e41f4b71Sopenharmony_ci### Functions 21e41f4b71Sopenharmony_ci 22e41f4b71Sopenharmony_ci| Name| Description| 23e41f4b71Sopenharmony_ci| -------- | -------- | 24e41f4b71Sopenharmony_ci| [OH_Telephony_GetDefaultCellularDataSlotId](ndk-apis-telephony-data.md#oh_telephony_getdefaultcellulardataslotid) | Obtains the default SIM card used for mobile data.| 25