What are kernels and what do kernels do?

The kernel is a program that comprises the central core of a computer operating   system. It has entire control over everything that take place in the system. The kernel is the primary part of the operating system to load into memory during booting (i.e., system startup), and it remains there for the whole duration of the computer session because its services are required continuously.

Kernels have two main functions:

1.   They provide program implementation points to make programs smaller.

2.   They handle errors thus the calculator does not lock up when an assembly program makes an error.