1. Is this a positive or a negative number?
1010 1001 0101 0101 0101 0111 1010 0101 0100 1000 1010 1010 1010 1011 1111 0101 is the binary representation of a negative integer, on 64 bits (8 Bytes).
In a signed binary, the first bit (the leftmost) is reserved for the sign,
1 = negative, 0 = positive. This bit does not count when calculating the absolute value.
2. Construct the unsigned binary number.
Exclude the first bit (the leftmost), that is reserved for the sign:
1010 1001 0101 0101 0101 0111 1010 0101 0100 1000 1010 1010 1010 1011 1111 0101 = 010 1001 0101 0101 0101 0111 1010 0101 0100 1000 1010 1010 1010 1011 1111 0101
3. Map the unsigned binary number's digits versus the corresponding powers of 2 that their place value represent:
262
0 261
1 260
0 259
1 258
0 257
0 256
1 255
0 254
1 253
0 252
1 251
0 250
1 249
0 248
1 247
0 246
1 245
0 244
1 243
0 242
1 241
1 240
1 239
1 238
0 237
1 236
0 235
0 234
1 233
0 232
1 231
0 230
1 229
0 228
0 227
1 226
0 225
0 224
0 223
1 222
0 221
1 220
0 219
1 218
0 217
1 216
0 215
1 214
0 213
1 212
0 211
1 210
0 29
1 28
1 27
1 26
1 25
1 24
1 23
0 22
1 21
0 20
1
4. Multiply each bit by its corresponding power of 2 and add all the terms up.
010 1001 0101 0101 0101 0111 1010 0101 0100 1000 1010 1010 1010 1011 1111 0101(2) =
(0 × 262 + 1 × 261 + 0 × 260 + 1 × 259 + 0 × 258 + 0 × 257 + 1 × 256 + 0 × 255 + 1 × 254 + 0 × 253 + 1 × 252 + 0 × 251 + 1 × 250 + 0 × 249 + 1 × 248 + 0 × 247 + 1 × 246 + 0 × 245 + 1 × 244 + 0 × 243 + 1 × 242 + 1 × 241 + 1 × 240 + 1 × 239 + 0 × 238 + 1 × 237 + 0 × 236 + 0 × 235 + 1 × 234 + 0 × 233 + 1 × 232 + 0 × 231 + 1 × 230 + 0 × 229 + 0 × 228 + 1 × 227 + 0 × 226 + 0 × 225 + 0 × 224 + 1 × 223 + 0 × 222 + 1 × 221 + 0 × 220 + 1 × 219 + 0 × 218 + 1 × 217 + 0 × 216 + 1 × 215 + 0 × 214 + 1 × 213 + 0 × 212 + 1 × 211 + 0 × 210 + 1 × 29 + 1 × 28 + 1 × 27 + 1 × 26 + 1 × 25 + 1 × 24 + 0 × 23 + 1 × 22 + 0 × 21 + 1 × 20)(10) =
(0 + 2 305 843 009 213 693 952 + 0 + 576 460 752 303 423 488 + 0 + 0 + 72 057 594 037 927 936 + 0 + 18 014 398 509 481 984 + 0 + 4 503 599 627 370 496 + 0 + 1 125 899 906 842 624 + 0 + 281 474 976 710 656 + 0 + 70 368 744 177 664 + 0 + 17 592 186 044 416 + 0 + 4 398 046 511 104 + 2 199 023 255 552 + 1 099 511 627 776 + 549 755 813 888 + 0 + 137 438 953 472 + 0 + 0 + 17 179 869 184 + 0 + 4 294 967 296 + 0 + 1 073 741 824 + 0 + 0 + 134 217 728 + 0 + 0 + 0 + 8 388 608 + 0 + 2 097 152 + 0 + 524 288 + 0 + 131 072 + 0 + 32 768 + 0 + 8 192 + 0 + 2 048 + 0 + 512 + 256 + 128 + 64 + 32 + 16 + 0 + 4 + 0 + 1)(10) =
(2 305 843 009 213 693 952 + 576 460 752 303 423 488 + 72 057 594 037 927 936 + 18 014 398 509 481 984 + 4 503 599 627 370 496 + 1 125 899 906 842 624 + 281 474 976 710 656 + 70 368 744 177 664 + 17 592 186 044 416 + 4 398 046 511 104 + 2 199 023 255 552 + 1 099 511 627 776 + 549 755 813 888 + 137 438 953 472 + 17 179 869 184 + 4 294 967 296 + 1 073 741 824 + 134 217 728 + 8 388 608 + 2 097 152 + 524 288 + 131 072 + 32 768 + 8 192 + 2 048 + 512 + 256 + 128 + 64 + 32 + 16 + 4 + 1)(10) =
2 978 383 095 975 816 181(10)
5. If needed, adjust the sign of the integer number by the first digit (leftmost) of the signed binary:
1010 1001 0101 0101 0101 0111 1010 0101 0100 1000 1010 1010 1010 1011 1111 0101(2) = -2 978 383 095 975 816 181(10)
The number 1010 1001 0101 0101 0101 0111 1010 0101 0100 1000 1010 1010 1010 1011 1111 0101(2) converted from a signed binary (base two) and written as an integer in decimal system (base ten):
1010 1001 0101 0101 0101 0111 1010 0101 0100 1000 1010 1010 1010 1011 1111 0101(2) = -2 978 383 095 975 816 181(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.