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By operating system control hardware
Phenomenon :
In the C language and other high-level programming language developed Windows applications, we rarely have access to the instructions directly control hardware.
Conclusion :
hardware control is solely responsible for the Windows, Windows provides a method by applying the indirect control hardware. Using the system call functionality provided by the operating system can be achieved control of the hardware. In Windows, the system calls called API (Application Programming Interface, Application Programming Interface)
Figure:
## Hardware generic term
I / O controllers : the inside of each connector is connected to the IC exchange current characteristic between the host computer with peripheral devices. These IC, collectively referred to as I / O controller
Port : I / O controller has a memory for temporarily saving data input and output. This memory is the port
port (port) literally means "harbor." Because the port is like a cargo port (data) handling between the host computer and peripheral equipment, so hence the name.
Port Number : distinguishing between the ports by the port number. The port number is also called I / O address.
Figure:
Interrupt mechanism
Definitions : IRQ (Interrupt Request) is used to pause the program currently running, and jump to the mechanisms necessary to run other programs, known as the interrupt handler
Examples :
start from interrupt processing request to interrupt the program (interrupt handler) until the end of the run, the handler (the main program) is interrupted is stopped. This situation is similar to a call comes in during the processing of the document, is equivalent to telephone interrupt processing.
If there is no interrupt function, then it must wait until the document is processed before they can receive calls. This too inconvenient.
Thus, interrupt handling has great value. After just finished answering the phone back to the original document, like a job, after the end of the interrupt handler runs, the processing returns to the main program will continue
Figure:
Role : use interrupt mechanism to achieve real-time processing? (Brainstorming)
For example :
If the main program are investigating whether mouse input, then if the keyboard input occurs, how to handle it? The results will inevitably lead character keyboard input can not be displayed in real time on the display. And by using the interrupt, you can achieve a real-time display
Text and picture display mechanism
The VRAM (the RAM Connections Video) : the display memory have been stored in the information display. This memory is called VRAM (Video RAM)
Action : in the program, as long as data is written to the VRAM, the data will be displayed in the display
Stage :
graphics and other dedicated hardware are generally configured with main memory with
independent VRAM and GPU (Graphics Processing Unit, a graphics processor, graphics chip is also referred to). This is because Windows is often necessary for drawing graphics, the number of megabytes of VRAM is required. In order to enhance the speed of the graphics drawing, and sometimes requires a dedicated graphics processor. In any case, the data stored in the memory VRAM is the message, this mechanism is displayed on the display is unchanged
