BITS, BYTES, MEGA, GIGA, TERA (EXPLAINED)

KNOWLEDGE BASE

1 bit = a 1 or 0 (b)
4 bits = 1 nibble (?)
8 bits = 1 byte (B)
1024 bytes = 1 Kilobyte (KB)
1024 Kilobytes = 1 Megabyte (MB)
1024 Megabytes = 1 Gigabyte (GB)
1024 Gigabytes = 1 Tera-byte (TB)

Common prefixes:
- Kilo, meaning 1,000. (one thousand) 10^3 (Kilometer, 1,000 meters)
- Mega, meaning 1,000,000. (one million) 10^6 (Megawatt, 1,000,000 watts)
- Giga, meaning 1,000,000,000 (one billion) 10^9 (Gigawatt, 1,000,000,000 watts)
- Tera, meaning 1,000,000,000,000 (one trillion) 10^12

The smallest amount of transfer is one bit. It holds the value of a 1, or a 0. (Binary coding). Eight of these 1's and zero's are called a byte.

Why eight? The earliest computers could only send 8 bits at a time, it was only natural to start writing code in sets of 8 bits. This came to be called a byte.

A bit is represented with a lowercase "b," whereas a byte is represented with an uppercase "b" (B). So Kb is kilobits, and KB is kilobytes. A kilobyte is eight times larger than a kilobit.

A simple 1 or 0, times eight of these 1's and 0's put together is a byte. The string of code: 10010101 is exactly one byte. So a small gif image, about 4 KB has about 4000 lines of 8 1's and 0's. Since there are 8 per line, that's over (4000 x 8) 32,000 1's and 0's just for a single gif image.

How many bytes are in a kilobyte (KB)? One may think it's 1000 bytes, but its really 1024. Why is this so? It turns out that our early computer engineers, who dealt with the tiniest amounts of storage, noticed that 2^10 (1024) was very close to 10^3 (1000); so based on the prefix kilo, for 1000, they created the KB. (You may have heard of kilometers (Km) which is 1000 meters). So in actuality, one KB is really 1024 bytes, not 1000. It's a small difference, but it adds up over a while.

The MB, or megabyte, mega meaning one million. Seems logical that one mega (million) byte would be 1,000,000 (one million) bytes. It's not however. One megabyte is 1024 x 1024 bytes. 1024 kilobytes is called one Megabyte. So one kilobyte is actually 1024 bytes, and 1024 of those is (1024 x 1024) 1048576 bytes. In short, one Megabyte is really 1,048,576 bytes.

There is a difference of about 48 KB, which is a decent amount. If you have a calculator, you will notice that there is actually a 47KB difference. There is a difference of 48,576 bytes, divided by 1024, and you get the amount of real kilobytes... 47.4375

All of this really comes into play when you deal with Gigabytes, or roughly one billion bytes. One real Gigabyte is actually 1024 bytes x 1024 bytes x 1024 bytes...1,073,741,824. However, most people like to simplify this by simply saying that one Gigabyte is only 1,000,000,000 (one billion) bytes; which makes sense because the prefix Giga means one billion.

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References
http://physics.nist.gov/cuu/Units/binary.html

INTERNET PROTOCOL (IP) ADDRESS

HOW IP ADDRESS WORKS

Every machine on a network has a unique identifier. Just as you would address a letter to send in the mail, computers use the unique identifier to send data to specific computers on a network. Most networks today, including all computers on the internet, use the TCP/IP protocol as the standard for how to communicate on the network. In the TCP/IP protocol, the unique identifier for a computer is called its IP address.



  

In Microsoft Windows, you can enter ipconfig in the command

 prompt app to view your computer's current IP address configuration.

Within an isolated network, you can assign IP addresses at random as long as each one is unique. However, connecting a private network to the Internet requires using registered IP addresses (called Internet addresses) to avoid duplicates.


There are two standards for IP addresses: IP Version 4 (IPv4) and IP Version 6 (IPv6). All computers with IP addresses have an IPv4 address, and many are starting to use the new IPv6 address system as well. Lets have a look at the differences.

• IPv4 uses 32 binary bits to create a single unique address on the network. An IPv4 address is expressed by four numbers separated by dots. Each number is the decimal (base-10) representation for an eight-digit binary (base-2) number, also called an octet. For example: 216.27.61.137.

• IPv6 uses 128 binary bits to create a single unique address on the network. An IPv6 address is expressed by eight groups of hexadecimal (base-16) numbers separated by colons, as in 2001:cdba:0000:0000:0000:0000:3257:9652. Groups of numbers that contain all zeros are often omitted to save space, leaving a colon separator to mark the gap (as in 2001:cdba::3257:9652).

At the dawn of IPv4 addressing, the Internet was not the large commercial sensation it is today, and most networks were private and closed off from other networks around the world. When the Internet exploded, having only 32 bits to identify a unique Internet address caused people to panic that we'd run out of IP addresses. Under IPv4, there are 232 possible combinations, which offers just under 4.3 billion unique addresses. IPv6 raised that to a panic-relieving 2128 possible addresses. Later, we'll take a closer look at how to understand your computer's IPv4 or IPv6 addresses.


How does your computer get its IP address? An IP address can be either dynamic or static. A static address is one that you configure yourself by editing your computer's network settings. This type of address is rare, and it can create network issues if you use it without a good understanding of TCP/IP. Dynamic addresses are the most common. They're assigned by the Dynamic Host Configuration Protocol (DHCP), a service running on the network. DHCP typically runs on network hardware such as routers or dedicated DHCP servers.



Dynamic IP addresses are issued using a leasing system, meaning that the IP address is only active for a limited time. If the lease expires, the computer will automatically request a new lease. Sometimes, this means the computer will get a new IP address, too, especially if the computer was unplugged from the network between leases. This process is usually transparent to the user unless the computer warns about an IP address conflict on the network (two computers with the same IP address). An address conflict is rare, and today's technology typically fixes the problem automatically.

 In the next lessons, we will look at the classes of IP address...