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CCNA Hexidecimal Help

By ghstinshll ·
Does anyone have any "mini-lessons" they would be willin to write up about how to deal with hex in the CCNA material?

What is the decimal & Hex equivalent of the Binary number 00001111... (or something like that) No matter how many times I read the section in Lammle's Sybex book I still don't have a solid unerstanding.

Any URLs would be appreciated. Thanks!

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Examples

by TheChas In reply to CCNA Hexidecimal Help

Binary Hex Decimal

0000 0 0
0001 1 1
0010 2 2
0011 3 3
0100 4 4
0101 5 5
0110 6 6
0111 7 7
1000 8 8
1001 9 9
1010 A 10
1011 B 11
1100 C 12
1101 D 13
1110 E 14
1111 F 15

The key is the place values for binary.

0001 1's place
0010 2's place
0100 4's place
1000 8's place

Break each binary number down into 4 place slices, starting at the least significant place, and convert to hex.

There is a technique called the double dabble method to convert binary to decimal. But, it has been over 20 years since I used it.

Chas

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Links

by TheChas In reply to Examples

I sure wish that TR did not remove spaces from postings.
The columns of numbers were much easier to read with the extra spaces.

Anyhow, here are a couple of links I found on Binary and double dabble.

http://www.tcnj.edu/~sampath/spring2003/lecture/Chapter8_I.doc

http://www.geocities.com/shanu_gupta2003/ns.html

In the first link, remove the space between Ch and apter8

Chas

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That's what happened to my post!

by Oz_Media In reply to Links

"I sure wish that TR did not remove spaces from postings."
And I couldn't even give Chas the bumps on his brthday! :-(

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Are you in a hex? Here's some help

by hotzelj In reply to CCNA Hexidecimal Help

I hate the fact that Cisco wont let you bring in a calculator to convert between number systems - how many people can do that quickly? I can, but just not fast - even for simple numbers.

To convert a hex number to decimal is easy.
0 - 9 in hex = 0 - 9 decimal
A - F in hex = 10 to 15 in decimal
Each place equals 16-to-the-power-of the place (remember that we start at the right and go left, and the first place is power-0 not power-1). So if you have the hex string "A" then you know it is 10 * 16^0 or 10. If it was "1B" then you know that it is 1 * 16^1 + B(or 11) * 16^0, the total is 16 + 11 = 27.

Now, how about converting decimal to binary?

Easy.

Same technique, however we are at base-2 not base-16, so instead of 16^1 we use 2^1.

The number 10(dec) in binary is 1010.
Why?

This is not the number 1,010, it is actaully 1 * 2^3 + 0 * 2^2 + 1 * 2^1 + 0 * 2^0. Do the math:
1 * 2^3 = 8, and 1 * 2^1 = 2, add together, 8+2, and the total is the answer - 10. Forget about anything that is "0" in binary, because we would do this 8 + 0 + 2 + 0, the end result is the same, so it makes it shorter to write out.

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convert everything to decimal first

by bharms In reply to CCNA Hexidecimal Help

0000 = 0 = 0x0
0001 = 1 = 0x1
0010 = 2 = 0x2
0011 = 3 = 0x3
0100 = 4 = 0x4
0101 = 5 = 0x5
0110 = 6 = 0x6
0111 = 7 = 0x7
1000 = 8 = 0x8
1001 = 9 = 0x9
1010 = 10 = 0xA
1011 = 11 = 0xB
1100 = 12 = 0xC
1101 = 13 = 0xD
1110 = 14 = 0xE
1111 = 15 = 0xF

FROM RIGHT TO LEFT OF BINARY ADD UP THE VALUES OF THE 1's with a ^2 chart.

8 - 4 - 2 - 1
0 - 0 - 0 - 0

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