The computer system consists of two parts: hardware and software.
Hardware: The physical part of the computer.
Software: It is composed of programs with various special functions that people have compiled in advance.
Computer software can generally be divided into two categories: system software and application software.
System software, also called system program, is mainly used to manage the entire computer system.
Application software has become an application program, which is a variety of programs compiled by users according to the needs of the characters.
The performance of a computer depends on the sum of software and hardware functions.
Computer architecture refers to the attributes of the computer system that can be seen by programmers, such as instruction system, data type, addressing technology composition and I/O machine.
Computer composition refers to how to realize the attributes embodied in the computer architecture, including hardware details that are transparent to the programmer, such as the structure and function of each functional component of the computer system, and the interconnection method.
Features of von Neumann machines:
- The computer is composed of five components: arithmetic unit, controller, memory, input device, and output device;
- Instructions and data are stored in the memory with the same status and can be accessed by address;
- Instructions and data are expressed in binary;
- Instructions are composed of two parts: operation code and address code. The operation code is used to indicate the nature of the operation, and the address is used to indicate the location of the operand in the memory;
- Instructions are stored sequentially in the memory, usually automatically removed and executed in sequence;
- The machine is centered on the computing unit (original von Neumann machine)
Modern computers have transformed to memory-centric.
The arithmetic unit Jerry controller is collectively called the central processing unit cpu.
Input devices and output devices are collectively referred to as I/O devices.
The cpu and the main memory together can be called the host. I/O devices can also be called external devices.
In order to achieve access by address, two registers MAR and MDR must also be configured in the main memory.
MAR is the memory address register, used to store the address of the memory unit to be accessed.
MDR is a memory data register, which is used to store the code taken from a certain unit of the memory bank or the code to be stored in a certain storage unit, and its number of bits is equal to the length of the storage word.
The arithmetic unit includes at least three registers and an arithmetic logic unit ALU.
Among them, ACC is the accumulator, MQ is the multiplier register, and X is the operand register.
The three stages of the controller: fetch instructions, analyze, and execute.
The controller is composed of a program counter PC, an instruction register IR and a control unit CU.
PC is used to store the address of the instruction currently to be executed.
IR is used to store the current instruction.
Important technical indicators of computer hardware: machine word length, storage capacity, and computing speed.
The machine word length refers to the number of bits of data that the CPU can process at a time.
The main storage capacity refers to the total number of bits of the binary code stored in the main storage.
The auxiliary storage capacity is usually expressed in bytes.