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?
1110 0101 1101 1101 1111 1001 0000 0010 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.
1110 0101 1101 1101 1111 1001 0000 0010 - 1 = 1110 0101 1101 1101 1111 1001 0000 0001
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:
!(1110 0101 1101 1101 1111 1001 0000 0001) = 0001 1010 0010 0010 0000 0110 1111 1110
4. Map the unsigned binary number's digits versus the corresponding powers of 2 that their place value represent:
231
0 230
0 229
0 228
1 227
1 226
0 225
1 224
0 223
0 222
0 221
1 220
0 219
0 218
0 217
1 216
0 215
0 214
0 213
0 212
0 211
0 210
1 29
1 28
0 27
1 26
1 25
1 24
1 23
1 22
1 21
1 20
0
5. Multiply each bit by its corresponding power of 2 and add all the terms up.
0001 1010 0010 0010 0000 0110 1111 1110(2) =
(0 × 231 + 0 × 230 + 0 × 229 + 1 × 228 + 1 × 227 + 0 × 226 + 1 × 225 + 0 × 224 + 0 × 223 + 0 × 222 + 1 × 221 + 0 × 220 + 0 × 219 + 0 × 218 + 1 × 217 + 0 × 216 + 0 × 215 + 0 × 214 + 0 × 213 + 0 × 212 + 0 × 211 + 1 × 210 + 1 × 29 + 0 × 28 + 1 × 27 + 1 × 26 + 1 × 25 + 1 × 24 + 1 × 23 + 1 × 22 + 1 × 21 + 0 × 20)(10) =
(0 + 0 + 0 + 268 435 456 + 134 217 728 + 0 + 33 554 432 + 0 + 0 + 0 + 2 097 152 + 0 + 0 + 0 + 131 072 + 0 + 0 + 0 + 0 + 0 + 0 + 1 024 + 512 + 0 + 128 + 64 + 32 + 16 + 8 + 4 + 2 + 0)(10) =
(268 435 456 + 134 217 728 + 33 554 432 + 2 097 152 + 131 072 + 1 024 + 512 + 128 + 64 + 32 + 16 + 8 + 4 + 2)(10) =
438 437 630(10)
6. If needed, adjust the sign of the integer number by the first digit (leftmost) of the signed binary:
1110 0101 1101 1101 1111 1001 0000 0010(2) = -438 437 630(10)
The number 1110 0101 1101 1101 1111 1001 0000 0010(2), signed binary in two's (2's) complement representation, converted and written as an integer in decimal system (base ten):
1110 0101 1101 1101 1111 1001 0000 0010(2) = -438 437 630(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.