提高篇重定向原理（The principle of redirection is improved）.doc

提高篇重定向原理（The principle of redirection is improved） Redirect is since MSDOS was support command line features, and is responsible for input/output requests a specific command or statements generated by the default console handed over to the other to complete the equipment, its startup logo is redirection symbols (including , , three, see their respective significance [1]) appeared in the sentence. General command line program input and output are defined by internal requests three port (referred to as the handle in the NT, undefined) under DOS, respectively output standard input stdin, stdout, stderr standard error. They usually point to the console (console, code for CON), where stdin points to the consoles keyboard, and stdout/stderr points to the consoles monitor. Thus, the console typically refers to the combination of the keyboard and monitor, which is a concept embodied in the terminal of the early mainframe. The stdin can be redirection, stdout can be , redirect, and stderr under DOS not redirect directly, only through ctty or other system control commands to other devices, indirectly. Device means a device driver or port code that controls the hardware or port of a PC, which is usually implemented and supported by the underlying or hardware driver of the system. Such as IO. SYS console CON, system CLOCK CLOCK $, unknown device CONFIG $first, the first serial AUX, parallel PRN, all COM1 serial port ~ COM4, all parallel port LPT1 ~ LPT3, available drive A: - X: and the empty equipment NUL mentioned above. There are many other devices, such as the XMSXXXX0 of himem.sys, EMM386. EXE implementation of EMMXXXX0, IFSHLP. SYS implementation of IFS $HLP $, etc. In these devices, few of the input and output information can be processed, only CON, NUL, and the serial port or parallel device connected with input and output hardware (printer, MODEM, etc.). They are called character device, and the disk file as a special character device column to choose among them, t