Subnetting Example 9

Convert decimal into binary

Example 9:

We have to find out binary value in given decimal number 220 and tell me which class it comes from ?

Note: You should always follow from left to right

Solution:

It comes from class C value given in above

Base position    2^7  2^6  2^5  2^4  2^3  2^2  2^1  2^0
Decimal value   128   64   32    16     8     4      2      1     
Binary value         1      1     0      1      1     1     0       0


After completing we can check by adding all "1"s given below;

128 + 64 + 16 + 8 + 4 = 220 

Rough note:

We can do this adding method given below;

Decimal calculations                                                         Bit in binary
128 is less than 220                                                                on the bit
128 + 64 = 192 is less than to 220                                          on the bit
128 + 64 + 32 = 224 is greater than 200                                 off the bit
128 + 64 + 0 + 16 = 208 is less than 220                                on the bit
128 + 64 + 0 + 16 + 8 = 216 is less than 220                          on the bit
128 + 64 + 0 + 16 + 8 + 4 = 220 is equivalent to 220              on the bit
128 + 64 + 0 + 16 + 8 + 4 + 2 = 222 is greater than 220         off the bit
128 + 64 + 0 + 16 + 8 + 4 + 0 + 1 = 221 is greater than 220   off the bit

This is another way of doing through subtracting method which is done in a simple and easy way given below;

Decimal calculation                                                            Bit in binary
220 - 128 = 92 is less than 220                                                on the bit
92 - 64 = 28 is less than 220                                                    on the bit
28 - 32 cannot be subtracted                                                   off the bit
28 - 16 = 12 is less than 220                                                    on the bit
12 - 8 = 4 is less than 220                                                        on the bit
4 - 4 = 0 is less than 220                                                          on the bit
0 - 2 cannot be subtracted                                                       off the bit
0 - 1 cannot be subtracted                                                       off the bit


Therefore, this is our binary value 11011100.