4.3: Binary Addition
Exam Board:
Eduqas / WJEC
Specification:
2016 +
What is binary addition?
Binary addition is a method of adding binary values without having to convert them into denary.
How to add binary numbers:
Overflow Errors
What is an overflow error?
An overflow error occurs when a binary value is too large to be stored in the bits available.
In technical terms, an overflow error occurs if a carry (remainder) is present on the most significant bit (MSB).
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The CPU then sets the overflow flag to true.
The most significant bit (MSB) is the largest bit (always the one furthest to the left) of a binary value (e.g. 128 for an 8 bit value).
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A flag is an alert signal. It is either on or off. The overflow flag is turned on by the CPU when an overflow occurs.
Questo's Questions
4.3  Binary Addition:
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1a. Describe the terms 'most significant bit' and 'flag'. [2]
1b. Using the terms from 1a, explain what an overflow error is. [2]
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2. Add together the following binary values. If an overflow error occurs you must state one has occurred.

a. 010110012 and 010001012 [2]

b. 110110112 and 010111012 [2]

c. 001101102 and 011010112 [2]

d. 110110112 and 010101112 [2]

e. 011011012 and 110101102 [2]