Computer network Basics-Operating system

First, why should have an operating system?

   Modern computer systems are complex systems consisting of one or more processors, main memory, disks, printers, keyboards, mouse monitors, network interfaces, and a variety of other input and   output devices, and each programmer is not in a position to master the details of all system implementations, and managing to optimize these components is a highly   challenging 's work. So, we need to install a layer of software for the computer, become the operating system, the task is the user program to provide a simple and clear computer model   , and manage all the above devices.   the definition is there: the operating system is a system program that coordinates, manages, and controls the hardware and software resources of the computer, located between the hardware and the application.              (a program is a software that runs on a system, such as a browser, a music player, and so on.)    definition of the kernel of the operating system: the kernel of the operating system is a management and control program that manages all the physical resources of the computer, including: File    unification, memory management, device management, and process management.

Ii. Operating system History 2.1 vacuum tube with punch card (no operating system)

Process: All-    purpose programmers load the perforated paper tape (or card) corresponding to the program and data into the input machine, then start the input machine to enter the program and data into the computer    memory, and then through the console Switch launcher program to run against the data, the calculation is completed, the printer output calculation results , the user takes the result and unloads the paper tape (or    card) before letting the next user on the machine.    Note:        1 programmer needs to make an appointment on a wall chronograph 2 at the         same time only one program in the memory is run by the CPU (serial)    pros and Cons:    advantages: The programmer in the time period of the application to enjoy the entire resources, and immediately debug their own programs , if there is a bug can be dealt with on the spot, the    disadvantage: This is a waste for the computer provider (you buy a computer 4000 pieces, that year you use 365 than only 1 days, it must be cost-saving, the use of the most    )

2.2 Transistors and batch processing systems

A generation of computer problems:    Too many human interaction (Input---> Calculation---> Output  input---> Calculation---> Output input---> Calculation---> Output)    Workaround:        Save a bunch of people's input into a large wave of input, and then in order to calculate (this is problematic, but the second generation of the calculation is not resolved) and then save the results into        a large wave output, this is the batch system    OS predecessor:    after collecting about one hours of batch work, The cards are read into the tape and then the tapes are sent to the machine room and mounted on tape. The tapes are then sent to the    machine room and mounted on the tape drive. The operator then loads a special program (which is the predecessor of the modern operating system) that reads the first    job (job, one or a set of programs) from the tape and runs, its output is written to the second tape, and it is not printed. After each job finishes, the operating system automatically    reads the next job from the tape and runs. When a whole batch of work is finished, the operator goes to the input and output tapes, says the input tape to the next batch    , and the output tape to a 1041 machine for offline (not with the main computer online) printing    advantages: Batch processing    disadvantage: 1 figure in the middle and two little men  2 are still sequential computations

2.3 IC Chip and multi-channel program design

For the second generation of computer two major problems    developed spooling technology: The    card is taken to the machine room can quickly read the job from the card into the disk, so any time when a job ends, the operating system can be a job from the magnetic    tape read out, Running in an empty memory area, this technique is called simultaneous external device online operation: Spooling The technology is also used for output. When    this technique is used, it is not necessary to IBM1401 the machine, nor to move the tape to move (the middle two are unemployed), to strengthen the function of the operating system to    develop multi-channel programming, to solve the problem of sequential execution: on the    7094 machine (the machine running the program) , if the current job is suspended due to waiting for tape or other IO operations, the CPU is in a casual state until the IO operation is    complete, for CPU-intensive scientific calculation, IO operation is less, waste time is not obvious, for commercial data processing, IO Wait can reach 80%~90%, so must    Need to solve the CPU waste phenomenon.    solution: Divide the memory into several parts, each of which holds different jobs, as shown in 1-5. When a job waits for IO to complete, another job can    use the CPU and put enough jobs in memory, the CPU utilization can be close to 100%    at this time, the third-generation computer is suitable for large-scale scientific computing and busy business data processing, but in essence it is still a batch processing system.    while resolving issues such as these, multiple jobs must be completed at the end of the run to get results, often up to hours from the submission of a job to the result of the Operation    .    Imagine a scene: a June b June three programmers at the same time in the debugging program, once a June write a comma, it may take half a day to see the knot
    Because the result of B June is also calculated at the same time. Time must be long. Word: We're all working together. Data (tapes)    Many programmers miss their first-generation computers and can debug their programs on the fly. In order to meet the programmer will soon be able to get a response, there has been a time-sharing operating system        : multiple online terminal + multi-Channel technology    20 clients simultaneously loaded into memory, 17 in thinking, 3 in operation, the CPU in a multi-channel way to handle the memory of these 3 programs, Due to general customer submissions
    are short instructions and rarely time consuming, the index computer can provide fast and interactive services to many users, all of whom assume that they have exclusive
    Counting Machine Resources

2.4 Person Computer

With the development of LSI, each square centimeter of silicon chip can be integrated thousands of transistors, the era of personal computers came.

Computer network Basics-Operating system