Q. Define Strategy Procedure?

The strategy procedure is called when loaded into memory by DOS or whenever controlled device request service. The major purpose of the strategy is to save request header and its address for use by interrupt procedure.

The request header is used by DOS to communicate commands and other information to interrupt procedure in the device driver.

The request header comprises length of the request header as its first byte. This is essentialsince the length of request header differs from command to command. The return status word communicate information back to DOS from device driver.

The initialise driver command (00H) is always executed when DOS initialises device driver. Initialisation commands pass message to video display indicating that driver is loaded into system and returns to DOS the amount of memory required by the driver. You can only use DOS INT 21H functions 00H.