138 10 Original Code What are the reverse and complement codes?

Original code: 10001101

Reverse code: 11110010

Complement: 11110011

Basic concepts and calculation methods of original, inverse, and complement codes.

Before exploring why machines use complements, let's first understand the concepts of primary, inverse, and complement. For a number, the computer uses a certain encoding method to store it.

Original, inverse, and complement codes are encoding methods in which a specific number is stored by the machine.

Source code. The original code is the absolute value of the sign bit plus the truth value, that is, the first bit represents the symbol, and the rest of the bits represent the value.

For example, if it is an 8-bit binary:

1] original =1] original =

The first bit is the sign bit.

Since the first bit is a sign bit, the value range of an 8-bit binary number is:

Namely. The source code is the easiest representation for the human brain to understand and calculate.

Reverse code. The inverse code is expressed as:

The inverse of a positive number is itself.

The inverse of a negative number is based on its original code, the sign bit remains unchanged, and the rest of the bits are negated.

00000001] original =

00000001] anti.

10000001] original =

11111110] anti.

It can be seen that if an inverse code represents a negative number, the human brain cannot intuitively see its value.

Usually, it is converted to the original code and then calculated.

Complement. The complement is expressed as:

The complement of a positive number is itself.

The complement of a negative number is based on its original code, the symbol bit remains unchanged, the rest of the digits are negated, and finally +1

i.e. +1 on the basis of the reverse code).

00000001] original =

00000001] anti.

00000001] Supplement.

10000001] original =

11111110] anti.

11111111] Supplement.

For negative numbers, the complement representation is also impossible for the human brain to directly produce its value.

It is usually also necessary to convert the original code to calculate its value.

Convert to binary first.

Original code = 110001010 (the first 1 means a negative sign) Inverse code = 101110101 (negative inverse code except for the sign bit, the rest is inverted) Complement = 101110110 (negative complement = inverse code + 1).

128 does not have the original code and the reverse code.

and complement, but the complement is -128 to +127, so the complement of -128 should be 10000000, and -128 has no inverse code. - 128 = 1000 000.

Everything else is overflowing, and the value of the original code in the 8-bit integer ranges from -127 to +127, and the reverse code is also.

When the code length is 8 bits, the original code and the reverse code of 128 do not exist.

The complement of 128 can't be found with "take the negative plus one".

It must be found using the "definition of complement".

[ 128] Supplement 128 + 2 8

= 128 = 1000 0000 (binary).

127 is a negative number, and its complement is the original code 01111111, which is inverted to 10000000, plus one, and 10000001.

For example: -1] original code 10000001 inverse code bai111111110 complement duzhi 11111111

Original code 00000011 reverse code 00000011 complement 00000011

127] Original code 11111111 reverse code 10000000 complement 10000001

Original code 01111111 reverse code 01111111 complement 01111111

According to the length of one byte, the 8th bit (bit7) is the sign bit, bit7=0 is a positive number, and bit7=1 is a negative number;

The original code of 123 is: 01111011, put the symbol position 1, that is, the original code of -123: 11111011, and its reverse code.

00000100, complement.

+1 = 00000101

x = = 111 1011b

x] original = 1111 1011b

x] anti = 1000 0100b

x] complement = 1000 0101b

Expressed as an 8-digit fixed-point decimal place).

Original code: 1001 0111

Reverse code: 1110 1000

Complement Swift: 1110 1001

Original code: 1000 0100

Reverse code: 1111 1011

Complement: 1111 1100

Original code = reverse code = complement code = 0000 1100

Let's assume that the code length is eight digits.

23 = 1 0111 (binary.)

its complement. Minus one first:Reverse again:

1110 1001。That's the complement of 23. Lead width

To find the complement:Write the positive complement first, and then subtract one to take the negation.

Finding the complement does not involve the inverse symbol bit of the original code at all.

Computers, and do not use the original code and reverse code.

The original code is reversed, and it is useless. You areFind a flowerCome to the Great ZenIt is also useless to roll dust.

Then you don't have to ask for it.

The binary of 13 is 1101.

The binary of 13 2 is .

The binary of 13 4 is .

The binary of 13 128 is .

Several codes of positive numbers, all of which are the same, are all positive numbers.

So,The original code and the reverse complement of 13 128 are: 0000 1101.

If you are looking for 13 128, then their original code, reverse code and complement code are 0 if you are asking.

The original code of 13, the reverse code and the complement code are both 1101

The 128 original code inverse code and complement code are 10000000ps: the original code of the integer, the inverse code, the complement code, are all the same, the negative original code, the reverse code, the complement, not the same, the original code, the reverse code, the relationship between the complement code is to write the original code in binary first, except that the symbol bit is unchanged. It's the opposite of you, and the reverse code plus one is the complement.

Positive: The inverse code of a positive number is the same as the original code.

Negative number: The inverse code of the negative number, the symbol bit is "1", and the numerical part is inverted by bit.

For example: sign bits.

Numeric digits [+7] inverse=

b[-7]anti=

So the landlord took a closer look at the book, whether the 00011010 was +26 or a negative number.

Special provisions: The complement of -128 is 10000000, so the complement representation range of the signed byte is: -128---127

128 is not within the range of the table number, so there is no reverse code.

But -128 has a complement, and the number of tables for an 8-bit binary bit complement is: -128 x 127.

Why is there one more complement for the table range? The reason for this is that the truth value 0 corresponds to only one encoding in the complement code, while the truth value 0 corresponds to two encodings in the inverse code.

According to the length of one byte, the 8th bit (bit7) is the sign bit, bit7=0 is a positive number, and bit7=1 is a negative number;

The original code of 123 is: 01111011, put the symbol position 1, that is, the original code of -123: 11111011, its inverse code = 00000100, complement = inverse code + 1 = 00000101

x = = - 111 1011b

x] original = 1111 1011b

x] anti = 1000 0100b

x] complement = 1000 0101b

Expressed as an 8-digit fixed-point decimal place).