Calpurnia's cot shows how segregation is everywhere in Maycomb, including the Finch home.
We know that Aunt Alexandra has somewhere to sleep when she stays with them, suggesting that they have a spare bedroom. However, when Calpurnia stays with the Finches, she is not allowed to stay in the spare room.
The purpose and effect of Beowulf describing his own great deeds rely on showing how confident he is about his strength and bravery to fight the monster. In this way, he is demonstrating his honor and fearless pursues to others.
