Just watch this and think deeply about it. The more you think the more you learn. More on reddit.com

We humans normally think of numbers in base-10, probably because most of us have 10 fingers on our hands, although we tend to start counting with the number 1 (instead of zero). Anyway, the ten numbers in base-10 are the obvious 0,1,2,3,4,5,6,7,8 and 9. These 10 digits can be used to represent values greater than themselves when we start adding them, so 9 + 1 = 10. In binary, we're working with base-2. Unlike base-10, where the numbers go from 0-9, base-2 only has 2 numbers: 0 and 1. However, just like the above 9 + 1 = 10 you can add numbers together. It's a little easier to see this when you begin counting in binary. So lets do that real quick. On the left will be base-10 numbers and on the right will be base-2 (4-bit). 00 = 0000 01 = 0001 02 = 0010 03 = 0011 04 = 0100 05 = 0101 06 = 0110 07 = 0111 08 = 1000 09 = 1001 10 = 1010 11 = 1011 12 = 1100 13 = 1101 14 = 1110 15 = 1111 Hopefully you can see a pattern here. Just like in base-10 when you increase a value over the base the number begins to grow out and occupy multiple spaces. Because I was only using 4 bits to try and describe numbers, I limited myself to only being able to express 16 different numbers (0 through 15). You can't do much with that, so if we wanted to go higher, we'd declare the system to use something like 8-bits instead. Which would look like this (added zeros to help align rows): 000 = 00000000 001 = 00000001 002 = 00000010 004 = 00000100 008 = 00001000 016 = 00010000 032 = 00100000 064 = 01000000 128 = 10000000 And so on. See the pattern of ones progress from the right to the left? You can use this to help you quickly figure out how much a binary number is by adding the values for all the 1's in the number. So 10000001 would be 129. With 8-bits, we can have numbers as large as 255 (11111111). I suppose that brings us to octets. The whole purpose of octets (and hex) is to make binary more human readable. So instead of telling someone "My IP address is 10010101.10000000 etc." we can say actual numbers, like "192.168.1.1" IP4 addressing uses 8-bits per octet, so no number would ever be higher than 255. It's this limitation that is the primary reason we're starting to see a shift away from IPv4 and to start using IPv6 instead. IPv6 uses 128-bits (16-bits per octet) and represents each octet as a 4-digit-long base-16 number. Base-16 is just another number system which, like base-10, has all the normal numbers but with 6 letters added in that are also treated as numbers (just pretend they're really numbers). So 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F If we count up with hex on the left and binary on the right, this is what we'll get: 0 = 0000 1 = 0001 2 = 0010 3 = 0011 4 = 0100 5 = 0101 6 = 0110 7 = 0111 8 = 1000 9 = 1001 A = 1010 B = 1011 C = 1100 D = 1101 E = 1110 F = 1111 So by using base-16 instead of base-10 to describe base-2, you are saving a little bit of space, and that comes in handy when you're trying to read a 128-bit number to someone. More on reddit.com

No, that's what google's for. Programming isn't a test of memory, it's an application of knowledge. If you know what hex, octal, etc. are, it doesn't matter if you remember how to convert between them or have to look it up, the result is the same. More on reddit.com

Actually, computers use base-2 (binary). The reason is that it's much easier for circuits to represent only two values for each digit (think "off" and "on") than all 10 in decimal (or any other number). Programmers sometimes use octal, because each octal digit represents exactly three base-2 digits/bits (think base-1000 vs. base-10), but hexadecimal (base-16) is actually more common -- each "hex" digit represents exactly 4 bits. I hope that helped! More on reddit.com