Workflow of a computer

2. How did the computer run when it was first booted?
   1. Post (power on Self test), because the hardware is not intelligent, so it must be done by something;
   2. This kind of thing is the program, program = instruction + data;
   3. The program is loaded and placed in memory before it can be executed;
4. And where is the program?
   1. When booting, the program is placed in the external memory, for example: U disk, hard drive, floppy disk, etc...
6. So where do you find so many plates?
   1. Through the CTRL + ALT + INS View boot, there are n boot options, is in accordance with the order of the inside of the selected execution, if the first one has to choose the first, or the next, just find a can.
   2. For example: When reloading the system, we will put the USB stick in the first place, and then the computer will be based on the option to find the corresponding program from the USB stick, and then began to execute.
8. But at the beginning of the machine, the computer does not know what the disk, and the sequencing is the implementation of the program, then what to play the process?
   1. To solve this problem, for a computer, it must have an ability to bootstrap, with additional equipment (BIOS)
10. To understand the BIOS, you must understand the computer architecture
    1. The computer consists of five major parts
       1. Arithmetic: Responsible for logic and add and subtract operations;
       2. Controller: Notifies the operator where to access the data;
       3. Memory: Refers to memory, address the storage device, 8 bits (1 bytes), to the flat address method.
       4. Input device
       5. Output device
11. Why is it possible to operate?
    2. The main problem is to solve two problems
       1. From where to read
       2. And where did the results go after reading?
    3. Take an adder to do an example
       2. 650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M02/6C/AB/wKiom1VPWJLhjlDhAAIGuHD9wAE689.jpg "/>
       4. Where do I find addend? Summand
       6. Why is it only possible to recognize the binary and not recognize the decimal?
          1. Because the computer is using voltage to express information, it is difficult to determine 1,2,3,4 .... n Volts (whether integers or decimals)
          2. The advantage of binary is that as long as the expression 0: no power, 1: Power (simple, reduce the complexity of the setting)
          3. The circuit and the logical connection, namely the so-called circuit closed switch completes the computer logic operation and then turns the logical operation to the arithmetic operation (circuit closed logic arithmetic operation)
       8. How is electricity moving? How does the adder know if there is electricity on the line? Thus understanding 0, 1
          1. How is the electricity transmitted?
             1. Matter is made up of atoms, atoms are composed of electrons and nuclei, and in stable state there is no electricity, and after taking electrons, they are positively charged;
             2. The process of generating electricity: the electrons are forcibly taken away and the other side is negatively charged, and the current is from the negative to the positive.
             3. Electrons in the medium is a certain speed of transmission, why the daily life is immediately have electricity?
                1. Because atomic electrons are synchronized, the whole matter is made up of atoms, so we feel like an instant.
                2. So to know that the adder must have a continuous voltage, so that the operation, the output is.
       10. For the graph, if the number of n-bit addition, it would require n lines, it would be cumbersome, and because of hardware problems, it is possible to tolerate so many lines, so there is a line multiplexing, but how to know what kind of a line? So there is a control bit (control line), but if only one group, that is Addend and Summand are the same line, then Addend come in, Summand will cover the addend, so there is a register, the addend temporarily saved up.
       12. For the controller, through the control bus (instruction bus) to obtain control instructions, the controller must tell the operator in which storage unit to fetch data (data line), where the results are also indicated by the Controller, the controller to know where is empty, the free space to put in.
13. How do I tell the computer which device to read from? How does the core deal with the periphery?
    1. In order to know whether we have the operation, the computer to keep listening (polling), but the polling will waste a lot of resources (for example, if we do not move a day, but it is still a day to check AH), in order to save resources, do not listen, there are other mechanisms, that is, we have the operation of the time, tell the CPU Knock on the generation of electrical signals, notify it, hurriedly to see, the CPU will be interrupted, through the programmable interrupt controller can know which device, the beginning of the device and the programmable interrupt controller is connected by different lines, but there will also appear just said the problem, so the use of line multiplexing, In order to mark which device it is, the amount of interrupt line appears.
    2. The less interrupts the better.

Workflow of a computer