demand reading(or writing)

Method for performing input (or output) operations in which blocks of data are transferred to or from the central processor as needed for processing. No special arrangements are made for storing input or output data in buffer areas to allow operations to take place in parallel.; 執行輸入(或輸出)操作的方法,當需要處理時,此操作就把數據塊送傳給中央處理機或從 中央處理機傳送出來。對于可以進行并行操作的緩沖區中存儲輸入或輸出數據,不需要作特 殊的安排。