binary code :?

TeaBoy_2

im trying to get my head around binary code (for ip addresses), hate anything at all mathematical.
i'm ok changing the binary code to a number.
say 11010111 is 215. (128+64+0+16+0+4+2+1) but i cant work it out the other way. for example, how would i know what the binary is for 239?

its for an exam tomorrow. help would be much appreciated!

xio

Basically subtract the largest power of two from the number, and keep going...

eg..

239 - 128 = 111 (1)
111 - 64 = 47 (1)
47 - 32 = 15 (1)
15 - 16 = (not possible therefore 0)
15 - 8 = 7 (1)
7 - 4 = 3 (1)
3 - 2 = 1 (1)
1 - 1 = 0 (1)

so 239 = 11101111

superscaper

Xio's right, that's how I do it. Starting with largest binary, mark it as 1 for every number you can successfully subtract until you get down to 1.

albertross_2

keep dividing by 2 and note the remainder

http://www.groovyweb.uklinux.net/index.php?page_name=how%20to%20convert%20binary%20to%20decimal

or line up in a

1024 512 256 128 64 32 16 8 4 2 u

bat999

Hi TeaBoy

If you're using Windows...

Open up the Calculator (It's in Accessories)
Click 'View'
Click 'Scientific'
Click the 'Dec' radio button
Enter your decimal number
Click the 'Bin' radio button
Sorted
:cool:

ps I know you won't be able to take your pc into the exam, but it might help to check your answers while practicing.

TeaBoy_2

oh yeah, of course! thanks very much for the replies. makes sense now.

ariba10

There used to be a signature on here a few months back.

"There are 10 types of people. Those who understand binary and those who do not"

TeaBoy_2

i'm one of those who don't. i've spent all day trying to answer last years paper with the use of the internet and all my notes!! still struggling! god help me tomorrow.

DrSmutt

albertross wrote:

keep dividing by 2 and note the remainder

http://www.groovyweb.uklinux.net/index.php?page_name=how%20to%20convert%20binary%20to%20decimal

or line up in a

1024 512 256 128 64 32 16 8 4 2 u

This is the way Ive done it for years. Doing it this way will also help with dec to hex or hex to dec.

a hex example

number = 2C4F

32768 16384 8192 4096 2048 1024 512 256 128 64 32 16 8 4 2 1
0 0 1 1 1 1 0 0 0 1 0 0 1 1 1 1

lee634

DrSmutt wrote:

This is the way Ive done it for years. Doing it this way will also help with dec to hex or hex to dec.

a hex example

number = 2C4F

32768 16384 8192 4096 2048 1024 512 256 128 64 32 16 8 4 2 1
0 0 1 1 1 1 0 0 0 1 0 0 1 1 1 1

Hopefully you were just jotting down binary numbers as 2C4f in binary is actually 2 C 4 F
10 1100 0100 1111

DrSmutt

oops didnt double check it.