What Is Device Independent?

Device independence, that is, the application is independent of the specific physical device used. In order to achieve device independence, two concepts of logical device and physical device are introduced. In the application, a logical device name is used to request the use of a certain type of device; and when the system is actually executed, the physical device name must also be used. Therefore, the system must have the function of converting a logical device name to a physical device name, which is very similar to the concept of logical addresses and physical addresses introduced in memory management.

Device independence

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Device independence, that is, the application is independent of the specific use

Equipment independence application advantages

The benefit of device independence is that the user has nothing to do with the physical peripherals, and the program does not have to be modified when the system is added or deleted or the peripherals are changed; it is easy to deal with the failure of the input and output devices. One replacement can even be replaced by different types of equipment such as tape drives or disk drives, thereby improving the reliability of the system, increasing the flexibility of peripheral device allocation, making more efficient use of peripheral device resources, and implementing multiple programming techniques .

After the operating system provides device-independent features, programmers can use logical devices for line input and output, and the conversion between logical devices and physical devices is usually implemented by operating system commands or languages. Due to the different sizes and functions of the operating system, there are differences in the conversion from logical devices to physical devices. Generally, the following methods are used: using job control language to implement device conversion in batch processing systems, using operation commands to implement device conversion, and using high-level language statements Achieve device conversion.

Device independence means that the operating system treats all external devices as files. As long as their drivers are installed, any user can manipulate and use these devices like files, without having to know their specific existence.

After implementing the function of device independence, it can bring two benefits: (1) flexibility in device allocation; (2) easy to implement I / O redirection (referring to the device used for I / O operations can be replaced Ie redirect without having to change the application).

How to achieve device independence

In order to achieve device independence, the concepts of logical and physical devices should be introduced. In the application, a logical device name is used to request the use of a certain type of device; while the system is executed, the physical device name is used. Since the driver is a software that is closely related to the hardware (or device), a layer of software must be set on the driver, called device independence software, to perform the public operations of all devices, complete the logical device name to the physical device name Conversion (a logical device table should be set up for this purpose) and provide a unified interface to the user layer (or file layer) software to achieve device independence.