What are the steps to convert the signed binary in two's (2's) complement representation to an integer in decimal system (in base ten)?
1. Is this a positive or a negative number?
1011 0111 0100 1110 1100 0100 1110 1010 is the binary representation of a negative integer, on 32 bits (4 Bytes).
- 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 = 01; 1 - 0 = 1; 1 - 1 = 0.
Subtract 1 from the initial binary number.
1011 0111 0100 1110 1100 0100 1110 1010 - 1 = 1011 0111 0100 1110 1100 0100 1110 1001
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:
!(1011 0111 0100 1110 1100 0100 1110 1001) = 0100 1000 1011 0001 0011 1011 0001 0110
4. Map the unsigned binary number's digits versus the corresponding powers of 2 that their place value represent:
231
0 230
1 229
0 228
0 227
1 226
0 225
0 224
0 223
1 222
0 221
1 220
1 219
0 218
0 217
0 216
1 215
0 214
0 213
1 212
1 211
1 210
0 29
1 28
1 27
0 26
0 25
0 24
1 23
0 22
1 21
1 20
0
5. Multiply each bit by its corresponding power of 2 and add all the terms up.
0100 1000 1011 0001 0011 1011 0001 0110(2) =
(0 × 231 + 1 × 230 + 0 × 229 + 0 × 228 + 1 × 227 + 0 × 226 + 0 × 225 + 0 × 224 + 1 × 223 + 0 × 222 + 1 × 221 + 1 × 220 + 0 × 219 + 0 × 218 + 0 × 217 + 1 × 216 + 0 × 215 + 0 × 214 + 1 × 213 + 1 × 212 + 1 × 211 + 0 × 210 + 1 × 29 + 1 × 28 + 0 × 27 + 0 × 26 + 0 × 25 + 1 × 24 + 0 × 23 + 1 × 22 + 1 × 21 + 0 × 20)(10) =
(0 + 1 073 741 824 + 0 + 0 + 134 217 728 + 0 + 0 + 0 + 8 388 608 + 0 + 2 097 152 + 1 048 576 + 0 + 0 + 0 + 65 536 + 0 + 0 + 8 192 + 4 096 + 2 048 + 0 + 512 + 256 + 0 + 0 + 0 + 16 + 0 + 4 + 2 + 0)(10) =
(1 073 741 824 + 134 217 728 + 8 388 608 + 2 097 152 + 1 048 576 + 65 536 + 8 192 + 4 096 + 2 048 + 512 + 256 + 16 + 4 + 2)(10) =
1 219 574 550(10)
6. If needed, adjust the sign of the integer number by the first digit (leftmost) of the signed binary:
1011 0111 0100 1110 1100 0100 1110 1010(2) = -1 219 574 550(10)
The number 1011 0111 0100 1110 1100 0100 1110 1010(2), signed binary in two's (2's) complement representation, converted and written as an integer in decimal system (base ten):
1011 0111 0100 1110 1100 0100 1110 1010(2) = -1 219 574 550(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.