The document discusses different number systems used in digital electronics and computing. It explains that number systems have different bases and describe the bases of common number systems like decimal, binary, octal and hexadecimal. Decimal uses base 10, binary uses base 2, octal uses base 8 and hexadecimal uses base 16. It provides details on how to convert between these different number systems both for whole numbers and fractions using various techniques like multiplying/dividing by the base, grouping bits or hexadecimal digits. Examples are given to illustrate the conversion methods between the different number systems.