9618 · 1.1
Data Representation flashcards
Revision flashcards for Cambridge 9618 Data Representation (syllabus 1.1). Flip, recall, then mark a real past-paper question.
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What is a bit?
The smallest unit of data in a computer, representing a single binary value of either 0 or 1.
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How many bits are in a byte?
8 bits. A byte can represent $2^8 = 256$ different values (0-255).
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What is hexadecimal used for?
To provide a more human-friendly representation of binary data. It's shorter and less error-prone to read than long binary strings. Used in memory dumps, MAC addresses, and colour codes.
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Convert the 4-bit binary number `1101` to denary.
(1 × 8) + (1 × 4) + (0 × 2) + (1 × 1) = 8 + 4 + 0 + 1 = 13.
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What is the key difference between ASCII and Unicode?
ASCII uses 7 or 8 bits and covers English characters and symbols. Unicode uses a variable number of bits (e.g., 8, 16, 32) and aims to represent every character from every language in the world.
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What is Two's Complement?
A method for representing signed integers (positive and negative) in binary. The most significant bit (MSB) indicates the sign.
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In 8-bit two's complement, what does the Most Significant Bit (MSB) signify?
It signifies the sign. If the MSB is 0, the number is positive. If the MSB is 1, the number is negative.
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How do you find the negative equivalent of a positive binary number using two's complement?
1. Invert all the bits (0s become 1s, 1s become 0s). 2. Add 1 to the result.
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What is an overflow error?
An error that occurs when the result of an arithmetic operation is too large to be stored in the number of bits allocated. For example, adding two positive 8-bit numbers and getting a result that requires 9 bits.
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What is the denary range of an 8-bit unsigned integer?
0 to 255. The formula is 0 to $2^8 - 1$.
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What is the denary range of an 8-bit signed integer using two's complement?
-128 to +127. The formula is from $-2^{7}$ to $2^{7} - 1$.