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| Another way of storing integers
is to use Two's Complement representation.
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Example To represent the number -13 as an 8-bit binary number... Step 1 : Convert the positive number 13 into an 8-bit binary integer:
Step 2 : Change all the bits from 0 to 1 (or from 1 to 0.)
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Step 3 : Add 1 - Perform a binary calculation.
Final answer : -13 in binary (using two's complement notation) is 11110011
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Remember when adding in binary that 1 + 1 = 10 1 + 1 + 1 = 11 etc... |
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A strange system???? Yes...but the arithmetic works! Consider our example ....... The number 13 is represented as 00001101 and -13 is represented as 11110011 What do we get if we add these two numbers together (we should get 0)?
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Another problem..... How does the computer know if a number is positive or negative? Does 11110011 represent -13 or does it represent (128+64+32+16+2+1) = 243? The usual system is - the first (left) bit represents a sign bit (0 means the number is positive and 1 means it is negative).
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