[工学]计算机导论-讲稿2.ppt

Store –40 in a 16-bit memory location using two’s complement representation. First change the number to binary 101000. Add ten 0s to make a total of N (16) bits, 0000000000101000. The sign is negative, so leave the rightmost 0s up to the first 1 (including the 1) unchanged and complement the rest. The result is:  1111111111011000 Solution Example 13 Example of storing two’s complement integers in two different computers Decimal------------ +7 -7 +124 -124 +24,760 -24,760 8-bit allocation ------------1111100110000100 overflow overflow 16-bit allocation ---------------------------- 0000000000000111 1111111111111001 0000000001111100 1111111110000100 0110000010111000 1001111101001000 Interpretation How do you interpret a twos complement binary represen-tation in decimal? The process involves these steps: 1. If the leftmost bit is 0 (positive number), a. Change the whole number from binary to decimal. b. Put a plus sign (+) in front of the number . 2. If the leftmost bit is 1 (negative number), a. Leave the rightmost bits up to the first 1 (inclusive) unchanged. Complement the rest of the bits. b. Change the whole number from binary to decimal. c. Put a negative sign (-) in front of the number. Interpret in decimal if the number was stored as a two’s complement integer. The leftmost bit is 1. The number is negative. Leave 10 at the right alone and complement the rest. The result is. The two’s complement number is 10. So the original number was –10. Solution Example 14 Summary of integer representation Contents of Memory------------ 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 Unsigned ------------ 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Sign-and-Magnitude --------- +0 +1 +2 +3 +4 +5 +6 +7 -0 -1 -2 -3 -4 -5 -6 -7 One’sComplement --------- +0 +1 +2 +3 +4 +5 +6 +7 -7 -6 -5 -4 -3 -2 -1 -0 Two’sComplement ---