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What is -1 two's complement?

Updated: 8/11/2023
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It is all 1's, no matter how many bits you have. The first 1 is for the negative sign, and you can think of the rest of the number being all 1's, because -1 is the highest negative whole number, then as you go down the negative whole numbers from there, (-2, -3, -4), etc you count backwards from there (always keeping the first 1 as a 1 for the negative sign).

Another way to get a negative number's two complement is to flip all the 1's and 0's, make the first bit a 1, and add 1 to the number

When you add a positive number and a negative form of that number, you get all 0's with a 1 carried to the far left of the number. If for example you have 2 eight bit numbers, one positive and one is 2's complement negative of the positive number

(eg: 2 + -2), it gets all 0's with 1 carried outside of the number - so in a computer it get represented as a 0 (because the 1 gets lost - since these are only 8 bit numbers each)

So the 2 compliment's system makes sense in more then one way.

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How do you write a program to determine whether a number is odd or even counter?

For positive integers, if the least significant bit is set then the number is odd, otherwise it is even. For negative integers in twos-complement notation, if the least significant bit is set then the number is odd, otherwise it is even. Twos-complement is the normal notation, allowing a range of -128 to +127 in an 8-bit byte. For negative integers in ones-complement notation, if the least significant bit is set then the number is even, otherwise it is odd. Ones-complement is less common, allowing a range of -127 to +127 in an 8-bit byte, where 11111111 is the otherwise non-existent value -0 (zero is neither positive nor negative). Ones-complement allows you to change the sign of a value simply by inverting all the bits. Twos-complement is the same as ones-complement but we also add one. Thus the twos complement of 0 is 0 because 11111111 + 1 is 0 (the overflowing bit is ignored). 11111111 then becomes -1 rather than the non-existent -0.


Signed binary subtraction 000000111001-111010000101 equals 000110101110 right?

Wrong. You don't say whether you are using ones-complement notation or twos-complement notation, but in either case you'd be wrong. Your answer of 000110101110 is 430 decimal, but the correct answer is 435 or 436 depending on which notation you use. Ones-complement notation: 000000111001 - 111010000101 = 000110110011 Decimal equivalent: 57 - (-378) = 57 + 378 = 435 Twos-complement notation: 000000111001 - 111010000101 = 000110110100 Decimal equivalent: 57 - (-379) = 57 + 379 = 436 Note that in ones-complement, converting the sign of any value simply inverts all the bits. So if we invert 111010000101 we get 000101111010 which is 378, thus the original signed value was -378. In twos complement we invert all the bits (as per ones-complement) and add 1, so 000101111010 + 1 is 000101111011 is 379, thus the original signed value was -379. QED.


What is unsigned data types in turbo c?

The same as an unsigned type in any other implementation of C. An unsigned type is an integer that is guaranteed positive. Normally, the most-significant bit of an integer denotes the sign (positive or negative). Unsigned types use this bit to denote value, effectively doubling the range of positive values over that of the signed equivalent. For instance, a signed char has a guaranteed range of -127 to +127 while an unsigned char has a guaranteed range of 0 to 255. Note that a signed char typically has a valid range of -128 to +127, however this is only true on systems that utilise twos-complement notation. Those that use the older ones-complement notation have two representations for the value zero (one positive, one negative). Ones-complement simply inverts all the bits of a value to switch the sign of a value, whereas twos-complement adds the value 1 after inverting all the bits. The value zero is denoted as 00000000 in binary. Inverting the bits creates 11111111, which is minus zero on a ones-complement system and -1 on a twos-complement system. -1 + 1 is 0, hence we add 1 on a twos-complement system.


How is the two's complement representation used?

The "twos complement" is that marvelous manipulation of bits in computer binary code that allows the computer to subtact by adding. It would be difficult to explain the whole picture, but computers can really do nothing but add. So the natural question is, how do they then calculate differences? Two's complement is the answer.


What is meant by ones-compliment of a decimal number?

One-complement applies to binary values, not decimal values. Therefore when we say the ones-complement of a decimal value we mean convert the value to binary, invert all the bits (the ones-complement), then convert the result back to decimal. For example, the decimal value 42 has the following representation in 8-bit binary: 00101010 If we invert all the bits we get 11010101 which is 213 decimal. Thus 213 is the ones-complement of 42, and vice versa. However, it's not quite as straightforward as that because some (older) systems use ones-complement notation to represent signed values, such that 11010101 represents the decimal value -42. The problem with this notation is that the ones-complement of 00000000 is 11111111 which means the decimal value 0 has two representations, +0 and -0 respectively. In the real-world, zero is neither positive nor negative. To resolve this problem, modern systems use twos-complement to represent signed values. The twos-complement of any value is simply the ones-complement plus one. Thus the ones-complement of 42 becomes -43, therefore the twos-complement of 42 is -43+1 which is -42. Thus -42 is represented by the binary value 11010110 in twos-complement notation. With twos-complement, there is only one representation for the value 0. This is because the ones-complement of 00000000 is 11111111 and if we add 00000001 we get 00000000. Note that we don't get 100000000 because the result cannot have any more bits than were in the original value. When an "overflow" occurs, we cycle back to zero. As a result, incrementing and decrementing signed values has exactly the same logic as incrementing or decrementing unsigned values and flipping the sign of any value is only slightly more complicated by the extra addition operation. However, flipping the sign of a value is a much rarer operation than counting so the cost is trivial compared to the cost of counting operations using ones-complement (because there are two values for zero). Note that ones-complement notation allows an 8-bit value to store signed values in the range -127 to +127, whereas twos-complement allows a range of -128 to +127 (through the elimination of the extra zero). But in unsigned notation, both allow the same range: 0 to 255. Although we rarely encounter ones-complement notation, it is important to keep in mind that not all systems use twos-complement notation, particularly when working with low-level but portable programming languages. This is the reason why both the C and the C++ standards state that the range of an 8-bit signed value is only guaranteed to store values in the range -127 to +127.

Related questions

What is the number 0111111111111111 in twos complement?

100000000000001


How do you programme Twos complement in binary in c?

int complement (int n) { return -n; } or int complement (int n) { return ~n+1; } both does the same thing.


The twos complement of 11001101 is?

00110011 is the 2's complement for this unsigned number and 10110011 if this is a signed number


How do you write a program to determine whether a number is odd or even counter?

For positive integers, if the least significant bit is set then the number is odd, otherwise it is even. For negative integers in twos-complement notation, if the least significant bit is set then the number is odd, otherwise it is even. Twos-complement is the normal notation, allowing a range of -128 to +127 in an 8-bit byte. For negative integers in ones-complement notation, if the least significant bit is set then the number is even, otherwise it is odd. Ones-complement is less common, allowing a range of -127 to +127 in an 8-bit byte, where 11111111 is the otherwise non-existent value -0 (zero is neither positive nor negative). Ones-complement allows you to change the sign of a value simply by inverting all the bits. Twos-complement is the same as ones-complement but we also add one. Thus the twos complement of 0 is 0 because 11111111 + 1 is 0 (the overflowing bit is ignored). 11111111 then becomes -1 rather than the non-existent -0.


Signed binary subtraction 000000111001-111010000101 equals 000110101110 right?

Wrong. You don't say whether you are using ones-complement notation or twos-complement notation, but in either case you'd be wrong. Your answer of 000110101110 is 430 decimal, but the correct answer is 435 or 436 depending on which notation you use. Ones-complement notation: 000000111001 - 111010000101 = 000110110011 Decimal equivalent: 57 - (-378) = 57 + 378 = 435 Twos-complement notation: 000000111001 - 111010000101 = 000110110100 Decimal equivalent: 57 - (-379) = 57 + 379 = 436 Note that in ones-complement, converting the sign of any value simply inverts all the bits. So if we invert 111010000101 we get 000101111010 which is 378, thus the original signed value was -378. In twos complement we invert all the bits (as per ones-complement) and add 1, so 000101111010 + 1 is 000101111011 is 379, thus the original signed value was -379. QED.


What is unsigned data types in turbo c?

The same as an unsigned type in any other implementation of C. An unsigned type is an integer that is guaranteed positive. Normally, the most-significant bit of an integer denotes the sign (positive or negative). Unsigned types use this bit to denote value, effectively doubling the range of positive values over that of the signed equivalent. For instance, a signed char has a guaranteed range of -127 to +127 while an unsigned char has a guaranteed range of 0 to 255. Note that a signed char typically has a valid range of -128 to +127, however this is only true on systems that utilise twos-complement notation. Those that use the older ones-complement notation have two representations for the value zero (one positive, one negative). Ones-complement simply inverts all the bits of a value to switch the sign of a value, whereas twos-complement adds the value 1 after inverting all the bits. The value zero is denoted as 00000000 in binary. Inverting the bits creates 11111111, which is minus zero on a ones-complement system and -1 on a twos-complement system. -1 + 1 is 0, hence we add 1 on a twos-complement system.


What is is the mixed number for three twos?

The answer to three twos is an integer and not a mixed number.


10 Why is twos complement usually used to represent integers?

The advantage of the two's complement method is that the procedure for adding or subtracting numbers is the same, whether the numbers are positive or negative. This makes the hardware for managing these numbers simpler.


How is the two's complement representation used?

The "twos complement" is that marvelous manipulation of bits in computer binary code that allows the computer to subtact by adding. It would be difficult to explain the whole picture, but computers can really do nothing but add. So the natural question is, how do they then calculate differences? Two's complement is the answer.


How do you find twos compliment of 00h in 8085 program?

You find the two's complement of 00H the same way you find it for any other number. You complement the bits and then you add 1. In the case of 00H, this results in 00H. That is no surprise, because -0 is the same as +0, and two's complement representation was chosen to do just that, as well as to make the physical addition of signed and unsigned numbers to be the same.


How many twos are in 16?

1


What is the Half twos?

The answer is 1/2.