Computer system

A computer system consists of software + hardware

1. External devices (input/output devices, external memory)


System software (operating system, language processing program, database management system, etc.) Application software (e.g. browser, file manager, video player, etc.)

Memory is divided into RAM, and ROM

0. The internal memory mainly stores the computer's currently running program, the data information used and the computing results, etc. Generally speaking, the memory capacity refers to the size of RAM, the contents of RAM can be read or written randomly, power off, the contents of RAM will be lost. 2.

In C, we often refer to allocated memory as RAM

The contents of a ROM are "read-only" and cannot be stored in it while the computer is running.

Programming language

  • Machine language, the binary zeros and ones, is the only language that can be understood and executed by a computer.
  • Assembly language, it is the computer instruction symbolization, can directly access the system interface.

    Computer instruction: The binary code that controls a computer
  • A high-level language, close to a natural language, needs to be translated by a compiler into a machine language target program, and then linked by a linker into an executable program
  • Program = Data Structure + Algorithm
  • Software = Program + Data + Documentation

The operating system

Operating system is a computer program that manages and controls computer hardware and software resources. It is the most basic system software that runs directly on the "bare computer". Any other software must be run under the support of the operating system.

The operating system is the interface between the user and the computer, as well as the interface between the computer hardware and other software.

Linux history

The first version of the UNIX operating system was written in the B language. From B came C, and UNIX was quickly rewritten in C. Linus Torvalds designed the first Linux based on Minix, a Unix-like system spin-off. Thus,Linux systems are written in C.
  • Remember, in Linux, everything is a file. Network interfaces, even mouse, keyboard and monitor are files

Everything in computer information can be represented with zeros and ones, including pixel display position (screen coordinates), pixel color (RGB values), sound (wavelengths), and so on, which determine the amount of images, text, video, audio, and so on on the screen, as well as the amount of display analogue.

  • Arithmetic Logic Unit is the executing Unit of the Central Processing Unit (CPU), the core building block of all CPUs, made up of “AND Gate” And” OR Gate”, The main function is to perform two-bit arithmetic operations, such as addition, subtraction and multiplication (not including integer division). Basically, in all modern CPU architectures, binary is represented as a complement.
  • A single latch or flip-flop can store a 1-bit binary number, so N latches or flip-flops can constitute an N-bit register