Science, Maths & Technology

### Become an OU student Discovering computer networks: hands on in the Open Networking Lab

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# 7.5 Summary of Session 7

In this part you’ve explored two number systems: decimal and binary. Through this exploration you’ve seen how counting can be done using a set quantity of symbols: 10 for the decimal system and 2 for the binary system. You’ve been introduced to the idea that other symbol sets can be used such as base 16 (hexadecimal) which you will meet later in the course. You’ve also seen how exponential notation can be used to signify the weighting applied to each symbol in a series of symbols representing large numbers. This can be used as mathematical shorthand to express large numbers.

You’ve been reminded that an IP address consists of a network portion and a host portion and that a subnet mask is used to indicate where the boundary between the two lies. You’ve seen how the use of Classless Inter-Domain Routing (CIDR) eliminates the previous octet boundaries of the subnet mask and by doing so makes more efficient use of network addresses. Finally, you’ve also seen how CIDR enables networks to be split into subnetworks for more efficient network management.

## New terms

In this session you have met the following terms.

 binary number system A number system based on two symbols: 0 and 1. CIDR notation A notation used to indicate the size of the network portion in an IP address. classful addressing An early IP addressing scheme in which the available network addresses were divided into five classes – A, B, C, D and E – based on octet boundaries. classless addressing The generic term used to describe the later IP addressing scheme in which the number of bits in the network portion became variable rather than fixed. Classless Inter-Domain Routing (CIDR) The name by which the classless addressing scheme is known. decimal number system A number system based on ten symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. exponential notation A mathematical shorthand for representing large numbers, also known as ‘scientific notation’. hexadecimal A number system based on sixteen symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F. octet A group of eight bits.