“The ideas about the meanings and explanations of the separate letters at the beginning of the Quranic Surahs from the perspective of the exegetists”

Twenty nine Surahs of the Qur’an are started with one or more of the alphabetic letters the most famous name of which is “Horuf Moqatta’ah” (separate letters). There are several issues propounded about these letters, like why they are included in the Qur’an, how they are pronounced, how many they are and their semantic relation with the verses coming after them. There are different explanations and interpretations put forward to clarify them due to their mysteriousness