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?
1010 1101 0001 0001 0000 0000 0100 0011 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.
1010 1101 0001 0001 0000 0000 0100 0011 - 1 = 1010 1101 0001 0001 0000 0000 0100 0010
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:
!(1010 1101 0001 0001 0000 0000 0100 0010) = 0101 0010 1110 1110 1111 1111 1011 1101
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
1 227
0 226
0 225
1 224
0 223
1 222
1 221
1 220
0 219
1 218
1 217
1 216
0 215
1 214
1 213
1 212
1 211
1 210
1 29
1 28
1 27
1 26
0 25
1 24
1 23
1 22
1 21
0 20
1
5. Multiply each bit by its corresponding power of 2 and add all the terms up.
0101 0010 1110 1110 1111 1111 1011 1101(2) =
(0 × 231 + 1 × 230 + 0 × 229 + 1 × 228 + 0 × 227 + 0 × 226 + 1 × 225 + 0 × 224 + 1 × 223 + 1 × 222 + 1 × 221 + 0 × 220 + 1 × 219 + 1 × 218 + 1 × 217 + 0 × 216 + 1 × 215 + 1 × 214 + 1 × 213 + 1 × 212 + 1 × 211 + 1 × 210 + 1 × 29 + 1 × 28 + 1 × 27 + 0 × 26 + 1 × 25 + 1 × 24 + 1 × 23 + 1 × 22 + 0 × 21 + 1 × 20)(10) =
(0 + 1 073 741 824 + 0 + 268 435 456 + 0 + 0 + 33 554 432 + 0 + 8 388 608 + 4 194 304 + 2 097 152 + 0 + 524 288 + 262 144 + 131 072 + 0 + 32 768 + 16 384 + 8 192 + 4 096 + 2 048 + 1 024 + 512 + 256 + 128 + 0 + 32 + 16 + 8 + 4 + 0 + 1)(10) =
(1 073 741 824 + 268 435 456 + 33 554 432 + 8 388 608 + 4 194 304 + 2 097 152 + 524 288 + 262 144 + 131 072 + 32 768 + 16 384 + 8 192 + 4 096 + 2 048 + 1 024 + 512 + 256 + 128 + 32 + 16 + 8 + 4 + 1)(10) =
1 391 394 749(10)
6. If needed, adjust the sign of the integer number by the first digit (leftmost) of the signed binary:
1010 1101 0001 0001 0000 0000 0100 0011(2) = -1 391 394 749(10)
The number 1010 1101 0001 0001 0000 0000 0100 0011(2), signed binary in two's (2's) complement representation, converted and written as an integer in decimal system (base ten):
1010 1101 0001 0001 0000 0000 0100 0011(2) = -1 391 394 749(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.