1. Is this a positive or a negative number?
1111 1111 1111 1111 1111 1111 1111 1111 1111 0000 1101 0110 0011 1010 1000 1100 is the binary representation of a negative integer, on 64 bits (8 Bytes).
In a signed binary in one's complement representation, the first bit (the leftmost) indicates the sign, 1 = negative, 0 = positive.
2. 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:
!(1111 1111 1111 1111 1111 1111 1111 1111 1111 0000 1101 0110 0011 1010 1000 1100) = 0000 0000 0000 0000 0000 0000 0000 0000 0000 1111 0010 1001 1100 0101 0111 0011
3. Map the unsigned binary number's digits versus the corresponding powers of 2 that their place value represent:
263
0 262
0 261
0 260
0 259
0 258
0 257
0 256
0 255
0 254
0 253
0 252
0 251
0 250
0 249
0 248
0 247
0 246
0 245
0 244
0 243
0 242
0 241
0 240
0 239
0 238
0 237
0 236
0 235
0 234
0 233
0 232
0 231
0 230
0 229
0 228
0 227
1 226
1 225
1 224
1 223
0 222
0 221
1 220
0 219
1 218
0 217
0 216
1 215
1 214
1 213
0 212
0 211
0 210
1 29
0 28
1 27
0 26
1 25
1 24
1 23
0 22
0 21
1 20
1
4. Multiply each bit by its corresponding power of 2 and add all the terms up.
0000 0000 0000 0000 0000 0000 0000 0000 0000 1111 0010 1001 1100 0101 0111 0011(2) =
(0 × 263 + 0 × 262 + 0 × 261 + 0 × 260 + 0 × 259 + 0 × 258 + 0 × 257 + 0 × 256 + 0 × 255 + 0 × 254 + 0 × 253 + 0 × 252 + 0 × 251 + 0 × 250 + 0 × 249 + 0 × 248 + 0 × 247 + 0 × 246 + 0 × 245 + 0 × 244 + 0 × 243 + 0 × 242 + 0 × 241 + 0 × 240 + 0 × 239 + 0 × 238 + 0 × 237 + 0 × 236 + 0 × 235 + 0 × 234 + 0 × 233 + 0 × 232 + 0 × 231 + 0 × 230 + 0 × 229 + 0 × 228 + 1 × 227 + 1 × 226 + 1 × 225 + 1 × 224 + 0 × 223 + 0 × 222 + 1 × 221 + 0 × 220 + 1 × 219 + 0 × 218 + 0 × 217 + 1 × 216 + 1 × 215 + 1 × 214 + 0 × 213 + 0 × 212 + 0 × 211 + 1 × 210 + 0 × 29 + 1 × 28 + 0 × 27 + 1 × 26 + 1 × 25 + 1 × 24 + 0 × 23 + 0 × 22 + 1 × 21 + 1 × 20)(10) =
(0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 134 217 728 + 67 108 864 + 33 554 432 + 16 777 216 + 0 + 0 + 2 097 152 + 0 + 524 288 + 0 + 0 + 65 536 + 32 768 + 16 384 + 0 + 0 + 0 + 1 024 + 0 + 256 + 0 + 64 + 32 + 16 + 0 + 0 + 2 + 1)(10) =
(134 217 728 + 67 108 864 + 33 554 432 + 16 777 216 + 2 097 152 + 524 288 + 65 536 + 32 768 + 16 384 + 1 024 + 256 + 64 + 32 + 16 + 2 + 1)(10) =
254 395 763(10)
5. If needed, adjust the sign of the integer number by the first digit (leftmost) of the signed binary:
1111 1111 1111 1111 1111 1111 1111 1111 1111 0000 1101 0110 0011 1010 1000 1100(2) = -254 395 763(10)
The signed binary number in one's complement representation 1111 1111 1111 1111 1111 1111 1111 1111 1111 0000 1101 0110 0011 1010 1000 1100(2) converted and written as an integer in decimal system (base ten):
1111 1111 1111 1111 1111 1111 1111 1111 1111 0000 1101 0110 0011 1010 1000 1100(2) = -254 395 763(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.