1e41f4b71Sopenharmony_ci# Telephony Data 2e41f4b71Sopenharmony_ci 3e41f4b71Sopenharmony_ci 4e41f4b71Sopenharmony_ci## Overview 5e41f4b71Sopenharmony_ci 6e41f4b71Sopenharmony_ciProvides C APIs for the cellular data module. 7e41f4b71Sopenharmony_ci 8e41f4b71Sopenharmony_ci**Since**: 13 9e41f4b71Sopenharmony_ci 10e41f4b71Sopenharmony_ci 11e41f4b71Sopenharmony_ci## Summary 12e41f4b71Sopenharmony_ci 13e41f4b71Sopenharmony_ci 14e41f4b71Sopenharmony_ci### File 15e41f4b71Sopenharmony_ci 16e41f4b71Sopenharmony_ci| Name| Description| 17e41f4b71Sopenharmony_ci| -------- | -------- | 18e41f4b71Sopenharmony_ci| [telephony_data.h](telephony__data_8h.md) | Defines C APIs for cellular data module.| 19e41f4b71Sopenharmony_ci 20e41f4b71Sopenharmony_ci### Functions 21e41f4b71Sopenharmony_ci 22e41f4b71Sopenharmony_ci| Name| Description| 23e41f4b71Sopenharmony_ci| -------- | -------- | 24e41f4b71Sopenharmony_ci| int32_t [OH_Telephony_GetDefaultCellularDataSlotId](#oh_telephony_getdefaultcellulardataslotid)(void) | Obtains the default SIM card used for mobile data.| 25e41f4b71Sopenharmony_ci 26e41f4b71Sopenharmony_ci## Function Description 27e41f4b71Sopenharmony_ci 28e41f4b71Sopenharmony_ci 29e41f4b71Sopenharmony_ci### OH_Telephony_GetDefaultCellularDataSlotId() 30e41f4b71Sopenharmony_ci 31e41f4b71Sopenharmony_ci``` 32e41f4b71Sopenharmony_ciint32_t OH_Telephony_GetDefaultCellularDataSlotId(void) 33e41f4b71Sopenharmony_ci``` 34e41f4b71Sopenharmony_ci 35e41f4b71Sopenharmony_ci**Description** 36e41f4b71Sopenharmony_ci 37e41f4b71Sopenharmony_ciObtains the default SIM card used for mobile data. 38e41f4b71Sopenharmony_ci 39e41f4b71Sopenharmony_ci**System capability**: SystemCapability.Telephony.CellularData 40e41f4b71Sopenharmony_ci 41e41f4b71Sopenharmony_ci**Since**: 13 42e41f4b71Sopenharmony_ci 43e41f4b71Sopenharmony_ci**Returns** 44e41f4b71Sopenharmony_ci 45e41f4b71Sopenharmony_ci**0**: card slot 1. 46e41f4b71Sopenharmony_ci 47e41f4b71Sopenharmony_ci**1**: card slot 2 48