Reading a RAW DATA or READING a DATA set

Could you explain, what is the difference between , SAS reading a raw data and SAS DATA step reading a SAS DATA set??
What does the " Read" and "Write" function implicate as far SAS data memory is concerned ?

Hi Vijay,

I have just completed the second chapter.
first of all we need to understand that SAS can only manage data made up of dataset. so when we reading a data from any source SAS will be storing this data resulted from reading to either Temp dataset or a permanent dataset.
so when we are reading data from raw data, SAS needs to create data dataset first (Input buffer, Program data vector and Data descriptor step used in DATA step) while in case of reading from Dataset this step not needed(Data is directly put in PDV).