Getting the Size of a Variable or Datatype using sizeof

This video explains the unary opetaor sizeof in c. It explains why the sizeof is used, how to use sizeof, what are the parameters required, how to use sizeof to get the sizeof int, float and char variable and then integer, float and char datatype.
And then it explains the usage of sizeof with structures, and addresses the issues like structure alignment,why compiler does structure alignment, how the struture alignment is done by the compiler.