§ Phần mềm Poll § cuộc thăm dò thường xuyên gián đoạn dịch vụ mỗi thiết bị để xem gây ra gián đoạn § bằng cách sử dụng một dòng lệnh riêng biệt trên hệ thống xe buýt (TESTI / O)? nâng cao TESTI / O? đặt địa chỉ mô-đun I / O trên dòng địa chỉ? | 51 Multiplication o Repeated Addition o Unsigned Integers Generating partial products shifting and adding Just like longhand multiplication Two s Complement Multiplication o Straightforward multiplication will not work if either the multiplier or multiplicand are negative multiplicand would have to be padded with sign bit into a 2n-bit partial product so that the signs would line up in a negative multiplier the 1 s and 0 s would no longer correspond to addshift s and shift-only s o Simple solution Convert both multiplier and multiplicand to positive numbers Perform multiplication Take 2 s complement of result if and only if the signs of original numbers were different Other methods do not require this final transformation step Booth s Algorithm Why does Booth s Algorithm work o Consider multiplying some multiplicand M by 30 M 00011110 which would take 4 shift-adds of M one for each 1 o That is the same as multiplying M by 32 - 2 M 00100000 - 00000010 M 00100000 - M 00000010 which would take 1 shift-only on no transition imagine last bit was 0 1 shift-subtract on the transition from 0 to 1 3 shift-only s on no transition 1 shift-add on the transition from 1 to 0 2 shift-only s on no transition o We can extend this method to any number of blocks of 1 s including blocks of unit length. o Consider the smallest number of bits that can hold the 2 s complement representation of -6 So we can clearly see that a shift-subtract at the leftmost 1-0 transition will cause 8 to be subtracted from the accumulated total which is exactly what needs to happen o This will expand to an 8-bit representation The neat part is that this same and only 1-0 transition will also cause -8 to be subtracted from the 8-bit version Division o Unsigned integers 00001101 Quotient Divisor 1011 10010011 Dividend 1011 001110 1011 001111 1011 100 Remainder Floating-Point Representation Principles o Using scientific notation we can store a floating point number in 3 parts S B E Sign Significand or .
