The first chapter of assembly language Basic knowledge

The evolution of computer language originates from machine language

Machine language

(1) is a collection of machine instructions. Machine instructions are binary information consisting of 0 and 1.

(2) Directly facing the machine, and the machine's hardware operation one by one corresponds. Computers can be directly identified, executed, using machine language can give full play to the computer's hardware functions.

(3) Disadvantage: Rely on machine hardware, machine instructions difficult to remember, direct use of machine language programming is very error-prone, and difficult to debug.

Because machine language is very difficult to identify and memory, so that the development of the entire industry has brought obstacles, resulting in assembly language.

Assembly

1) The main body of assembly language is assembly instruction.

(2) The difference between the assembly instruction and the machine instruction is the representation method of the instruction. The assembly instruction is a mnemonic of the machine instruction, which facilitates human memory and use.

(3) Different CPUs have different assembly instructions.

(4) Assembly language consists of three types of directives: assembly instructions, pseudo-directives, and other symbols.

Use:

(1) helps to understand how a computer works from a software perspective

(2) Assembly language has the ability to directly and effectively control the hardware, can write a fast running speed, low code volume of high-efficiency programs, in many cases have irreplaceable role, such as operating system core program section, real-time control system software, intelligent instrumentation procedures, frequently called subroutines or dynamic connection library, Encryption and decryption software, analysis and prevention of computer viruses and so on.

The computer has five main components: controller, arithmetic, input device, output device, memory.

Directives and data are only concepts in application. In memory or on disk, there is no difference between instructions and data, both binary information.

CPU-to-memory read/write

(1) The CPU is address bus to specify the memory unit.

(2) The data transfer between the CPU and the memory or other devices is carried out via the data bus.

(3) The control of the external device by the CPU is carried out by the control bus.

The width of the address bus determines the addressing capability of the CPU;

The width of the data bus determines the amount of data transmitted by the CPU and other devices during data transfer;

The width of the control bus determines the CPU's ability to control other devices in the system.

Memory address space

① memory address space is a logical concept;

② memory address space, which is the CPU addressing space, is directly related to the CPU address bus width;

The capacity of the ③ memory address space is not the same as the capacity of the memory bar which is usually spoken;

④ different computer systems how memory address space is used has different allocation schemes.

The first chapter of assembly language Basic knowledge