Convert 12 345 678 911 to a Signed Binary in Two's (2's) Complement Representation

How to convert decimal number 12 345 678 911(10) to a signed binary in two's (2's) complement representation

What are the steps to convert decimal number
12 345 678 911 to a signed binary in two's (2's) complement representation?

  • A signed integer, written in base ten, or a decimal system number, is a number written using the digits 0 through 9 and the sign, which can be positive (+) or negative (-). If positive, the sign is usually not written. A number written in base two, or binary, is a number written using only the digits 0 and 1.

1. Divide the number repeatedly by 2:

Keep track of each remainder.

We stop when we get a quotient that is equal to zero.


  • division = quotient + remainder;
  • 12 345 678 911 ÷ 2 = 6 172 839 455 + 1;
  • 6 172 839 455 ÷ 2 = 3 086 419 727 + 1;
  • 3 086 419 727 ÷ 2 = 1 543 209 863 + 1;
  • 1 543 209 863 ÷ 2 = 771 604 931 + 1;
  • 771 604 931 ÷ 2 = 385 802 465 + 1;
  • 385 802 465 ÷ 2 = 192 901 232 + 1;
  • 192 901 232 ÷ 2 = 96 450 616 + 0;
  • 96 450 616 ÷ 2 = 48 225 308 + 0;
  • 48 225 308 ÷ 2 = 24 112 654 + 0;
  • 24 112 654 ÷ 2 = 12 056 327 + 0;
  • 12 056 327 ÷ 2 = 6 028 163 + 1;
  • 6 028 163 ÷ 2 = 3 014 081 + 1;
  • 3 014 081 ÷ 2 = 1 507 040 + 1;
  • 1 507 040 ÷ 2 = 753 520 + 0;
  • 753 520 ÷ 2 = 376 760 + 0;
  • 376 760 ÷ 2 = 188 380 + 0;
  • 188 380 ÷ 2 = 94 190 + 0;
  • 94 190 ÷ 2 = 47 095 + 0;
  • 47 095 ÷ 2 = 23 547 + 1;
  • 23 547 ÷ 2 = 11 773 + 1;
  • 11 773 ÷ 2 = 5 886 + 1;
  • 5 886 ÷ 2 = 2 943 + 0;
  • 2 943 ÷ 2 = 1 471 + 1;
  • 1 471 ÷ 2 = 735 + 1;
  • 735 ÷ 2 = 367 + 1;
  • 367 ÷ 2 = 183 + 1;
  • 183 ÷ 2 = 91 + 1;
  • 91 ÷ 2 = 45 + 1;
  • 45 ÷ 2 = 22 + 1;
  • 22 ÷ 2 = 11 + 0;
  • 11 ÷ 2 = 5 + 1;
  • 5 ÷ 2 = 2 + 1;
  • 2 ÷ 2 = 1 + 0;
  • 1 ÷ 2 = 0 + 1;

2. Construct the base 2 representation of the positive number:

Take all the remainders starting from the bottom of the list constructed above.

12 345 678 911(10) = 10 1101 1111 1101 1100 0001 1100 0011 1111(2)

3. Determine the signed binary number bit length:

  • The base 2 number's actual length, in bits: 34.

  • A signed binary's bit length must be equal to a power of 2, as of:
  • 21 = 2; 22 = 4; 23 = 8; 24 = 16; 25 = 32; 26 = 64; ...
  • The first bit (the leftmost) indicates the sign:
  • 0 = positive integer number, 1 = negative integer number

The least number that is:

1) a power of 2

2) and is larger than the actual length, 34,

3) so that the first bit (leftmost) could be zero
(we deal with a positive number at this moment)

=== is: 64.


4. Get the positive binary computer representation on 64 bits (8 Bytes):

If needed, add extra 0s in front (to the left) of the base 2 number, up to the required length, 64.


Decimal Number 12 345 678 911(10) converted to signed binary in two's complement representation:

12 345 678 911(10) = 0000 0000 0000 0000 0000 0000 0000 0010 1101 1111 1101 1100 0001 1100 0011 1111

Spaces were used to group digits: for binary, by 4, for decimal, by 3.

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How to convert signed integers from decimal system to signed binary in two's complement representation

Follow the steps below to convert a signed base 10 integer number to signed binary in two's complement representation:

  • 1. If the number to be converted is negative, start with the positive version of the number.
  • 2. Divide repeatedly by 2 the positive representation of the integer number, keeping track of each remainder, until we get a quotient that is zero.
  • 3. Construct the base 2 representation of the positive number, by taking all the remainders starting from the bottom of the list constructed above. Thus, the last remainder of the divisions becomes the first symbol (the leftmost) of the base two number, while the first remainder becomes the last symbol (the rightmost).
  • 4. Binary numbers represented in computer language must have 4, 8, 16, 32, 64, ... bit length (a power of 2) - if needed, add extra bits on 0 in front (to the left) of the base 2 number above, up to the required length, so that the first bit (the leftmost) will be 0, correctly representing a positive number.
  • 5. To get the negative integer number representation in signed binary one's complement, replace all 0 bits with 1s and all 1 bits with 0s (reversing the digits).
  • 6. To get the negative integer number, in signed binary two's complement representation, add 1 to the number above.

Example: convert the negative number -60 from the decimal system (base ten) to signed binary in two's complement:

  • 1. Start with the positive version of the number: |-60| = 60
  • 2. Divide repeatedly 60 by 2, keeping track of each remainder:
    • division = quotient + remainder
    • 60 ÷ 2 = 30 + 0
    • 30 ÷ 2 = 15 + 0
    • 15 ÷ 2 = 7 + 1
    • 7 ÷ 2 = 3 + 1
    • 3 ÷ 2 = 1 + 1
    • 1 ÷ 2 = 0 + 1
  • 3. Construct the base 2 representation of the positive number, by taking all the remainders starting from the bottom of the list constructed above:
    60(10) = 11 1100(2)
  • 4. Bit length of base 2 representation number is 6, so the positive binary computer representation of a signed binary will take in this particular case 8 bits (the least power of 2 larger than 6) - add extra 0 digits in front of the base 2 number, up to the required length:
    60(10) = 0011 1100(2)
  • 5. To get the negative integer number representation in signed binary one's complement, replace all the 0 bits with 1s and all 1 bits with 0s (reversing the digits):
    !(0011 1100) = 1100 0011
  • 6. To get the negative integer number, signed binary in two's complement representation, add 1 to the number above:
    -60(10) = 1100 0011 + 1 = 1100 0100
  • Number -60(10), signed integer, converted from decimal system (base 10) to signed binary two's complement representation = 1100 0100