In a signed binary in two's complement representation, the first bit (the leftmost) indicates the sign, 1 = negative, 0 = positive.
2. Get the binary representation in one's complement.
* Run this step only if the number is negative *
Note on binary subtraction rules:
11 - 1 = 10; 10 - 1 = 1; 1 - 0 = 1; 1 - 1 = 0.
Subtract 1 from the initial binary number.
* Not the case - the number is positive *
3. Get the binary representation of the positive (unsigned) number.
* Run this step only if the number is negative *
Flip all the bits of the signed binary in one's complement representation (reverse the digits) - replace the bits set on 1 with 0s and the bits on 0 with 1s:
* Not the case - the number is positive *
4. Map the unsigned binary number's digits versus the corresponding powers of 2 that their place value represent:
231
0 230
0 229
1 228
0 227
0 226
1 225
1 224
0 223
1 222
0 221
0 220
0 219
1 218
0 217
1 216
1 215
0 214
0 213
1 212
1 211
0 210
0 29
0 28
0 27
0 26
0 25
1 24
1 23
0 22
0 21
1 20
1
5. Multiply each bit by its corresponding power of 2 and add all the terms up.
0010 0110 1000 1011 0011 0000 0011 0011(2) =
(0 × 231 + 0 × 230 + 1 × 229 + 0 × 228 + 0 × 227 + 1 × 226 + 1 × 225 + 0 × 224 + 1 × 223 + 0 × 222 + 0 × 221 + 0 × 220 + 1 × 219 + 0 × 218 + 1 × 217 + 1 × 216 + 0 × 215 + 0 × 214 + 1 × 213 + 1 × 212 + 0 × 211 + 0 × 210 + 0 × 29 + 0 × 28 + 0 × 27 + 0 × 26 + 1 × 25 + 1 × 24 + 0 × 23 + 0 × 22 + 1 × 21 + 1 × 20)(10) =
(0 + 0 + 536 870 912 + 0 + 0 + 67 108 864 + 33 554 432 + 0 + 8 388 608 + 0 + 0 + 0 + 524 288 + 0 + 131 072 + 65 536 + 0 + 0 + 8 192 + 4 096 + 0 + 0 + 0 + 0 + 0 + 0 + 32 + 16 + 0 + 0 + 2 + 1)(10) =
(536 870 912 + 67 108 864 + 33 554 432 + 8 388 608 + 524 288 + 131 072 + 65 536 + 8 192 + 4 096 + 32 + 16 + 2 + 1)(10) =
646 656 051(10)
6. If needed, adjust the sign of the integer number by the first digit (leftmost) of the signed binary:
0010 0110 1000 1011 0011 0000 0011 0011(2) = 646 656 051(10)
The signed binary number in two's complement representation 0010 0110 1000 1011 0011 0000 0011 0011(2) converted and written as an integer in decimal system (base ten):
0010 0110 1000 1011 0011 0000 0011 0011(2) = 646 656 051(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.