35、Likewise, we don,＇t () a refrigerator that knows when it＇s out of milk.

234、Input, output interface provides a method for transferring information between internal storage and external I/O devices.Peripherals connected to a computer need special communication links for interfacing them with the central processing unit.The purpose of the communication link is to resolve the differences that exist between the central computer and each peripheral.The major differences are:(1) Peripheral are, electromechanical and electromagnetic devices and their manner of operation is different from the operation of the CPU and memory, which are electronic devices.Therefore, a conversion of signal values may be required.(2) The data transfer rate of peripherals is usually slower than the transfer rate of the CPU, and consequently, a synchronization mechanism may be needed.(3) Data codes and formats in peripherals differ from the word format in the CPU and memory.(4) The operating modes of peripherals are different from each other and each must be controlled so as not to disturb the operation of other peripherals connected to the CPU.To resolve these differences, computer systems include special hardware components between the CPU and peripherals to supervise and synchronize all input and output transfers.These components are called interface units because they interface between the processor bus and the peripheral device.In addition, each device may have its own controller that supervises the operations of the particular mechanism in the peripheral.Each peripheral device has associated with an interface unit.Each interface decodes the address and control received from the I/O bus, interprets them for the peripheral, and provides signals for the peripheral controller.It also synchronizes the data flow and supervises the transfer between peripheral and processor.(2)、Why the hardware components used to supervise and synchronize data transfer are called “Interface unit”?

234、Input, output interface provides a method for transferring information between internal storage and external I/O devices.Peripherals connected to a computer need special communication links for interfacing them with the central processing unit.The purpose of the communication link is to resolve the differences that exist between the central computer and each peripheral.The major differences are:(1) Peripheral are, electromechanical and electromagnetic devices and their manner of operation is different from the operation of the CPU and memory, which are electronic devices.Therefore, a conversion of signal values may be required.(2) The data transfer rate of peripherals is usually slower than the transfer rate of the CPU, and consequently, a synchronization mechanism may be needed.(3) Data codes and formats in peripherals differ from the word format in the CPU and memory.(4) The operating modes of peripherals are different from each other and each must be controlled so as not to disturb the operation of other peripherals connected to the CPU.To resolve these differences, computer systems include special hardware components between the CPU and peripherals to supervise and synchronize all input and output transfers.These components are called interface units because they interface between the processor bus and the peripheral device.In addition, each device may have its own controller that supervises the operations of the particular mechanism in the peripheral.Each peripheral device has associated with an interface unit.Each interface decodes the address and control received from the I/O bus, interprets them for the peripheral, and provides signals for the peripheral controller.It also synchronizes the data flow and supervises the transfer between peripheral and processor.(1)、1.Why conversion of signal values is needed for communication link?

233、Machine language is the level of programming languages.

232、The computer system both hardware system and software system.

231、In computer science, a data structure is a way of data in a computer so that it can be used efficiently.

230、Brute-force algorithms typically take the direct or obvious route, without attempting to minimize the number of operations required to compute the solution.

229、This does not mean that the steps must be executed in a sequence consisting a first step, followed by a second, and so on.

228、An essential step in problem is to identity the underlying abstract problem devoid of all unnecessary detail.

227、Hard disk technology has steadily improved to keep pace storage demand.

226、 the process has no print heads that move or print hammers that fire, the result is high speed and quiet operation.