### How to Pass CIE A Level Computer Science (9618 AS & A Level)

Paper 1 - Theory Fundamentals
Information Representation
Multimedia
Compression
Networks including the Internet
Computer Hardware
Processor Fundamentals
System Software
Ethics and Ownership
Databases
Paper 2 - Problem Solving & Programming Skills
Algorithms
Data Types & Structures
Programming
Software Development
System Software
Paper 4 - Practical Programming
1 of 2

We talked about what binary is in the previous section, but making use of these numbers through binary addition allows the computer system to perform more complex tasks.

Adding binary digits together requires a set of simple rules that you likely learnt in primary school:

0 + 0 = 0

0 + 1 = 1

1 + 1 = 10   (2 in binary)

1 + 1 + 1 = 11   (3 in binary)

The process of adding binary numbers together requires you to use the same process as long addition in maths. Each time a number becomes more than one digit long, the digit is carried over to the next column.

This can be seen when adding the numbers 10 and 5 together.

First, convert both denary numbers to binary:

Now we can apply the rules of binary addition to each column from right to left. In this case, there are no columns that require us to carry any digits:

We can see here that once the rules have been applied, the resulting number adds up to the denary addition of the two numbers. We can check this by converting the result back to denary.

So what does it look like with a more complex calculation? Let’s try adding 7 and 12:

Notice that this time we have carried the 1 to the left where the rules state the answer is 10. This carried digit is then added as part of the next column.

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