As part of the iGCSE Computer Science course you will be required to convert binary numbers to and from denary, our base 10 number system..
In the video below, I introduce you to how these numbers are converted and how to show this in the exam.
We’ve already seen that binary uses powers of 2 to convert from Denary (base 10) to Binary (base 2), and using the conversion table below is a useful way to help you to convert as you will not have a calculator in your exam:
128Â 64Â 32Â 16Â 8Â 4Â 2Â 1
 0  0  1  0  1 0 1 0
In the table above, we’ve converted the number 42 into binary by placing the powers of 2 in different columns and placing a 1 under the numbers that you would use to add up to 42. So in this case: 32 + 8 + 2 = 42
We can use this process in reverse to convert a binary number back into denary by writing the powers of 2 over each digit and adding up the columns with a 1 in. If your binary number is longer than 8 digits (bits) just keep doubling the numbers in the columns!
Watch the video below for a recap on how to convert these numbers:
Activity
Once you have completed the video lesson at the top of the page, try the practice questions below:
If you would prefer to download the questions as a printable practice sheet, click the icon below:
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