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 1010 0000 0010 1000 1000 0010 1110 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 1010 0000 0010 1000 1000 0010 1110 - 1 = 1110 1010 0000 0010 1000 1000 0010 1101
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 1010 0000 0010 1000 1000 0010 1101) = 0001 0101 1111 1101 0111 0111 1101 0010
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
0 226
1 225
0 224
1 223
1 222
1 221
1 220
1 219
1 218
1 217
0 216
1 215
0 214
1 213
1 212
1 211
0 210
1 29
1 28
1 27
1 26
1 25
0 24
1 23
0 22
0 21
1 20
0
5. Multiply each bit by its corresponding power of 2 and add all the terms up.
0001 0101 1111 1101 0111 0111 1101 0010(2) =
(0 × 231 + 0 × 230 + 0 × 229 + 1 × 228 + 0 × 227 + 1 × 226 + 0 × 225 + 1 × 224 + 1 × 223 + 1 × 222 + 1 × 221 + 1 × 220 + 1 × 219 + 1 × 218 + 0 × 217 + 1 × 216 + 0 × 215 + 1 × 214 + 1 × 213 + 1 × 212 + 0 × 211 + 1 × 210 + 1 × 29 + 1 × 28 + 1 × 27 + 1 × 26 + 0 × 25 + 1 × 24 + 0 × 23 + 0 × 22 + 1 × 21 + 0 × 20)(10) =
(0 + 0 + 0 + 268 435 456 + 0 + 67 108 864 + 0 + 16 777 216 + 8 388 608 + 4 194 304 + 2 097 152 + 1 048 576 + 524 288 + 262 144 + 0 + 65 536 + 0 + 16 384 + 8 192 + 4 096 + 0 + 1 024 + 512 + 256 + 128 + 64 + 0 + 16 + 0 + 0 + 2 + 0)(10) =
(268 435 456 + 67 108 864 + 16 777 216 + 8 388 608 + 4 194 304 + 2 097 152 + 1 048 576 + 524 288 + 262 144 + 65 536 + 16 384 + 8 192 + 4 096 + 1 024 + 512 + 256 + 128 + 64 + 16 + 2)(10) =
368 932 818(10)
6. If needed, adjust the sign of the integer number by the first digit (leftmost) of the signed binary:
1110 1010 0000 0010 1000 1000 0010 1110(2) = -368 932 818(10)
The number 1110 1010 0000 0010 1000 1000 0010 1110(2), signed binary in two's (2's) complement representation, converted and written as an integer in decimal system (base ten):
1110 1010 0000 0010 1000 1000 0010 1110(2) = -368 932 818(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.