tailieunhanh - Schaum’s Outline Series OF Principles of Computer Science phần 3

Một số nguyên tắc bạn có thể khai báo đối với việc sử dụng đạo đức và phi đạo đức của máy tính và phần mềm là gì? 1,9 Danh sách một số cách quan trọng, trong đó máy tính đã góp phần vào phúc lợi của nhân loại. Những người, nếu có, đã phải chịu đựng từ sự tiến bộ của công nghệ điện toán? | 36 COMPUTER ORGANIZATION CHAP. 3 If the program expects to find a character it will try to interpret the bits as a character. If the bit pattern doesn t make sense as a character encoding either the program will fail or an error message will result. Likewise if the program expects an integer it will interpret the bit pattern as an integer even if the bit pattern originally encoded a character. It is incumbent on the programmer to be sure that the program s handling of data is appropriate. CPU ALU The CPU is the part of the computer one thinks of first when describing the components of a computer. The repetitive cycle of the von Neumann computer is to a load an instruction from memory into the CPU and b decode and execute the instruction. Executing the instruction may include performing arithmetic or logical operations and also loading or storing data in memory. When the instruction execution is complete the computer fetches the next instruction from memory and executes that instruction. The cycle continues indefinitely unless the instruction fetched turns out to be a HALT instruction. The CPU is usually described as consisting of a control unit and an arithmetic and logic unit ALU . The control unit is responsible for maintaining the steady cycle of fetch-and-execute and the ALU provides the hardware for arithmetic operations value comparisons greater than less than equal to and logical functions AND OR NOT etc. . Both the control unit and the ALU include special very high-performance memory cells called registers. Registers are intimately connected to the wiring of the control unit and the ALU some have a special purpose and some are general purpose. One special-purpose register is the program counter PC . The PC keeps track of the address of the instruction to execute next. When the control unit begins a fetch-execute cycle the control unit moves the instruction stored at the address saved in the PC to another special register called the instruction register IR .