The original code, complement code and inverse code of the algorithm (4)
[1] Original code, complement code and complement code are the coding methods for storing a specific number by the machine.
original code
[2] The original code is the absolute value of the sign bit + the true value, the first bit represents the sign bit, and the remaining bits represent the value.
For example:
An 8-bit binary
0000 0001 (1 original code)
1000 0001 (-1 original code)
8-bit binary representation range is
1111 1111-0111 1111（-127，127）
complement
The complement of a positive number is itself, and the complement of a negative number is based on its original code, with the sign bit unchanged and the rest inverted.
that is
0000 0001 (1 original code)---The complement is the same 0000 0001 (1 complement)
1000 0001 (-1 original code)---inverted code symbol bit unchanged, the rest of the inverted 1111 1110 (-1 inverted code), this number can not see what is represented, need to be converted to the original code to see.
complement
The complement of a positive number or itself,
The complement of a negative number is based on the original code, or the complement of the final +1.
[Summary]
Positive--complement (self)--complement (self)
Negative--complement (sign bit unchanged, rest inverted)--complement (complement +1)
[Example: ]
byte b = (byte) 130;
b = ?
[Analysis]
1. All operations in the computer are complementary.
2, calculate the binary data, 130 (default int type 4 bytes), that is, 1000010 (1 byte)
4-bit byte complement is:
000000 0000000 0000000 1000010 (positive-negative-original)
byte Truncate a byte, i.e.(1000010)---(complement)
3, complement to complement code 1000001
4. Reverse code to original code 1 111110 (-126)
[Expansion]
Here we analyze
byte b = (byte) 130;
b = -126;(byte-128: artificially specified-0 is-128----127)
Which means it's a loop, which means
127（127）
128 （-128）
129（-127）
130（-126）
131（-125）
.....
400（-112）
Calculation idea:
From-128--127 to 256
400-256=144（-112）
