Classification of io
input)
output)
by type:
byte stream
any file can be transmitted through byte stream.
character stream (Reader/Writer)
Non-pure text files cannot use character stream, which will lead to file format destruction and cannot be executed normally.
node stream (low-level stream: directly connected with input and output sources)
fileinputstream/fileoutputstream/filereader/filewriter/printstream/printwriter.
processing stream (high-level stream: based on low-level stream).
conversion stream: input streamreader/output streamwriter, byte stream character stream/character stream byte stream
buffer stream: buffered input stream/buffered output stream buffered reader/buffered reader can wrap the nodes flowing through the lines. Make reading and writing faster
A computer, commonly known as a computer, is an electronic computer used for high-speed calculation, which can perform numerical calculation as well as logical calculation, and also has the function of storage and memory. It is a modern intelligent electronic device that can run according to the program and process massive data automatically and at high speed. It is composed of hardware system and software system, and a computer without any software installed is called bare metal.
It can be divided into five categories: supercomputer, industrial control computer, network computer, personal computer and embedded computer. The more advanced computers include biological computer, photon computer, quantum computer and neural network computer. Protein computer, etc.
At present, the operation speed of computer system has reached trillions of times per second, and the microcomputer can reach hundreds of millions of times per second, which has solved a large number of complex scientific calculation problems. For example, the calculation of satellite orbit, the calculation of large dams, the calculation of 24-hour weather forecast, etc. In the past, manual calculation took several years and decades, but now it takes only a few days or even minutes to complete with computers.
the development of science and technology, especially the development of cutting-edge science and technology, requires highly accurate calculation. The reason why the missile controlled by computer can hit the predetermined target accurately is inseparable from the accurate calculation of the computer. A general computer can have more than a dozen or even dozens of significant digits (binary), and the calculation accuracy can range from a few thousandths to a few millionths, which is beyond the reach of any calculation tool.
With the increasing storage capacity of computers, more and more information can be stored and memorized. The computer can not only calculate, but also save the data, programs, intermediate results and final results for users to call at any time; You can also perform arithmetic and logical operations on various information (such as video, language, text, graphics, images, music, etc.) through coding technology, and even conduct reasoning and proof.
The internal operation of the computer is automatically controlled according to the pre-programmed programs. According to the needs of solving problems, the user designs the running steps and programs in advance, and the computer operates strictly according to the steps specified in the programs. The whole process is automatically executed without manual intervention, which has achieved the expected results of the users.
supercomputers usually refer to computers composed of hundreds of thousands or even more processors, which can calculate large-scale and complex problems that ordinary PCs and servers cannot complete. Supercomputer is a kind of computer with the strongest function, the fastest operation speed and the largest storage capacity, and it is an important symbol of the national scientific and technological development level and comprehensive national strength.
Supercomputers have the strongest parallel computing ability, which is mainly used for scientific computing. In meteorology, military, energy, aerospace, prospecting and other fields to undertake large-scale, high-speed computing tasks.
structurally, although both supercomputers and servers may be multiprocessor systems, there is no substantial difference between them. However, modern supercomputers mostly adopt cluster systems and pay more attention to the performance of floating-point operations. It can be seen that they are high-performance servers that focus on scientific computing and are very expensive.
The general super calculator consumes a lot of electricity, and the electricity bill is thousands per second. The CPU of the super calculator is at least 5 cores, which means it is about 1 times as fast as that of a home computer, but this kind of CPU is not available and costs tens of millions.