Learning by Doing: CISCO Certified Network ... - SCN Research

Our next one: 3 - 2 = 1. So we put a “1” under the 2 heading and move to the next
column heading.
2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0
128 64 32 16 8 4 2 1
1 1 0 1 1 1 1
Our next one: 1 - 1 = 0. So we put a “1” under the 1 heading.
2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0
128 64 32 16 8 4 2 1
1 1 0 1 1 0 0 1
And we are done…right? Wrong! We should always double-check our work. To do this
we convert from binary back to decimal. By adding the column headings:
128+64+16+8+4+2+1=223. It worked!
Let’s take a quick time out and let you try some decimal to binary conversions:
1. 84
2. 243
3. 24
4. 254
5. 179
Now let’s check your answers with the answer section. Did you get the right ones? I
certainly hope so. Try not to use a calculator. You will not be allowed to use one on the
CCNA test so get practice without it now. Notice in this lab we have been using 8 binary
numbers for our conversions. Each one of those binary numbers is called a “bit” and 8 of
them together (which is extremely common in computers) is called an “octet” or “byte.”
We can do conversions for more or less bits, but it is just a matter of adding more or less
columns to our bit-bashing table.
Supplemental Lab or Challenge Activity:
1. Make a binary to decimal conversion chart for all decimal numbers between 0 and
255.
2. Try to calculate the binary numbers for these decimal numbers:
a. 1024
b. 4096
c. 3333
d. 4309
e. 64768
3. See if you can find out what are hexadecimal, octal, gray code, and binary coded
decimal conversions.
4. You can make a “binary to decimal” self-tutoring aid using standard index cards.
On one side of the index card write a big “0” on it. On the other side write a big
“1” on it. Then arrange the index cards so all zeroes or all ones are facing up.
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