Convert 101 111 010 138 to a Signed Binary in Two's (2's) Complement Representation

How to convert decimal number 101 111 010 138(10) to a signed binary in two's (2's) complement representation

What are the steps to convert decimal number
101 111 010 138 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;
  • 101 111 010 138 ÷ 2 = 50 555 505 069 + 0;
  • 50 555 505 069 ÷ 2 = 25 277 752 534 + 1;
  • 25 277 752 534 ÷ 2 = 12 638 876 267 + 0;
  • 12 638 876 267 ÷ 2 = 6 319 438 133 + 1;
  • 6 319 438 133 ÷ 2 = 3 159 719 066 + 1;
  • 3 159 719 066 ÷ 2 = 1 579 859 533 + 0;
  • 1 579 859 533 ÷ 2 = 789 929 766 + 1;
  • 789 929 766 ÷ 2 = 394 964 883 + 0;
  • 394 964 883 ÷ 2 = 197 482 441 + 1;
  • 197 482 441 ÷ 2 = 98 741 220 + 1;
  • 98 741 220 ÷ 2 = 49 370 610 + 0;
  • 49 370 610 ÷ 2 = 24 685 305 + 0;
  • 24 685 305 ÷ 2 = 12 342 652 + 1;
  • 12 342 652 ÷ 2 = 6 171 326 + 0;
  • 6 171 326 ÷ 2 = 3 085 663 + 0;
  • 3 085 663 ÷ 2 = 1 542 831 + 1;
  • 1 542 831 ÷ 2 = 771 415 + 1;
  • 771 415 ÷ 2 = 385 707 + 1;
  • 385 707 ÷ 2 = 192 853 + 1;
  • 192 853 ÷ 2 = 96 426 + 1;
  • 96 426 ÷ 2 = 48 213 + 0;
  • 48 213 ÷ 2 = 24 106 + 1;
  • 24 106 ÷ 2 = 12 053 + 0;
  • 12 053 ÷ 2 = 6 026 + 1;
  • 6 026 ÷ 2 = 3 013 + 0;
  • 3 013 ÷ 2 = 1 506 + 1;
  • 1 506 ÷ 2 = 753 + 0;
  • 753 ÷ 2 = 376 + 1;
  • 376 ÷ 2 = 188 + 0;
  • 188 ÷ 2 = 94 + 0;
  • 94 ÷ 2 = 47 + 0;
  • 47 ÷ 2 = 23 + 1;
  • 23 ÷ 2 = 11 + 1;
  • 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.

101 111 010 138(10) = 1 0111 1000 1010 1010 1111 1001 0011 0101 1010(2)

3. Determine the signed binary number bit length:

  • The base 2 number's actual length, in bits: 37.

  • 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, 37,

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 101 111 010 138(10) converted to signed binary in two's complement representation:

101 111 010 138(10) = 0000 0000 0000 0000 0000 0000 0001 0111 1000 1010 1010 1111 1001 0011 0101 1010

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


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