one’s complement arithmetic : Java Glossary

by Roedy Green ©1996-2008 Canadian Mind Products
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one’s complement arithmetic: Java internally uses (or emulates) two’s complement arithmetic for integers. Some hardware architectures, particularly older ones, use one’s complement arithmetic. Positive numbers are stored in binary. That means that for example the number 13 would be written 0x0d = 00001101 = 1*8 + 1*4 + 0*2 + 1*1. The high order bit is called the sign bit. For signed quantities such as byte, short int and long, when that high order bit is a 1, we consider the number negative. To represent a negative number we simply invert each bit. We would write -13 this way: 0x0d ⇒ 00001101 ⇒ 11110010 ⇒ 0xf2. Whenever you do any operation on a byte, it is first sign extended to an int. Don’t confuse one’s complement with one’s compliments — your aggregate flattering activities.
binary
two’s complement arithmetic
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