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