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?
1100 0101 0010 0001 1001 0111 0110 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.
1100 0101 0010 0001 1001 0111 0110 1110 - 1 = 1100 0101 0010 0001 1001 0111 0110 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:
!(1100 0101 0010 0001 1001 0111 0110 1101) = 0011 1010 1101 1110 0110 1000 1001 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
1 228
1 227
1 226
0 225
1 224
0 223
1 222
1 221
0 220
1 219
1 218
1 217
1 216
0 215
0 214
1 213
1 212
0 211
1 210
0 29
0 28
0 27
1 26
0 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.
0011 1010 1101 1110 0110 1000 1001 0010(2) =
(0 × 231 + 0 × 230 + 1 × 229 + 1 × 228 + 1 × 227 + 0 × 226 + 1 × 225 + 0 × 224 + 1 × 223 + 1 × 222 + 0 × 221 + 1 × 220 + 1 × 219 + 1 × 218 + 1 × 217 + 0 × 216 + 0 × 215 + 1 × 214 + 1 × 213 + 0 × 212 + 1 × 211 + 0 × 210 + 0 × 29 + 0 × 28 + 1 × 27 + 0 × 26 + 0 × 25 + 1 × 24 + 0 × 23 + 0 × 22 + 1 × 21 + 0 × 20)(10) =
(0 + 0 + 536 870 912 + 268 435 456 + 134 217 728 + 0 + 33 554 432 + 0 + 8 388 608 + 4 194 304 + 0 + 1 048 576 + 524 288 + 262 144 + 131 072 + 0 + 0 + 16 384 + 8 192 + 0 + 2 048 + 0 + 0 + 0 + 128 + 0 + 0 + 16 + 0 + 0 + 2 + 0)(10) =
(536 870 912 + 268 435 456 + 134 217 728 + 33 554 432 + 8 388 608 + 4 194 304 + 1 048 576 + 524 288 + 262 144 + 131 072 + 16 384 + 8 192 + 2 048 + 128 + 16 + 2)(10) =
987 654 290(10)
6. If needed, adjust the sign of the integer number by the first digit (leftmost) of the signed binary:
1100 0101 0010 0001 1001 0111 0110 1110(2) = -987 654 290(10)
The number 1100 0101 0010 0001 1001 0111 0110 1110(2), signed binary in two's (2's) complement representation, converted and written as an integer in decimal system (base ten):
1100 0101 0010 0001 1001 0111 0110 1110(2) = -987 654 290(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.