| 释义 |
▪ I. ˈunderflow, n.
[under-1 5 c.]
1. An undercurrent. Also fig.
1854S. Dobell Balder xxiv. 169 That underflow and substance wherein the future heaves. 1875J. Croll Climate & T. viii. 133 An underflow of polar water south into the Atlantic.
2. The (more or less horizontal) flow of water through the ground, spec. underneath a river bed.
1890Rep. Secretary of Agric. 1890 (U.S. Dept. Agric.) 472 Papers on underflow and subterranean water. Ibid. 475 Mr. [J. W.] Gregory became convinced of the existence at moderate depths below the surface..of an almost continuous drainage supply, which he has termed the under-sheet or under-flow water. 1905U.S. Geol. Survey Water-Supply & Irrigation Papers No. 140. 85 Such wells, several hundred feet in depth, with perforations opposite the best water-bearing material, would utilize a large part of the underflow which now escapes to the sea. 1951H. E. Thomas Conservation of Ground Water iii. 138 Underflow is the only method of movement in certain reaches of some streams, where the surface channel is dry. 1970W. C. Walton Groundwater Resource Evaluation vi. 375 Water leaving basins includes streamflow, evapo-transpiration, and subsurface underflow.
3. Computing. [After overflow n. 2 d.] The generation of a number that is too small to be represented in the device meant to store it.
1959E. M. McCormick Digital Computer Primer xi. 155 A number which is too small (yet is not 0) will cause an ‘underflow’. 1970O. Dopping Computers & Data Processing vi. 102 In machines with automatic floating-point arithmetic..there may also be indicators for overflow and underflow in the characteristic. 1985Personal Computer World Feb. 182/2 Computer users pay far less attention to underflow than they do to overflow or rounding.
▪ II. underˈflow, v.
[under-1 4 a, b. Cf. OE. underflówan.]
1. intr. To flow beneath.
1610Holland Camden's Brit. ii. 45 It looketh downe to the underflowing sea. 1647Hexham i.
2. trans. To flow in under (something).
1872Dixon Switzers v. 45 The waters..underflowed the beams, and lifted the strong habitations.
3. intr. Computing. Usu. ˈunderflow. [Cf. prec., sense 3.] Of the result of an arithmetical operation: to become too small for the device meant to store it.
1965IBM Systems Jrnl. IV. 32 If the exponent underflows or the result fraction is zero, the result should be treated as ‘zero’. 1973C. W. Gear Introd. Computer Sci. ii. 73 Give examples of pairs of numbers A and B in internal form such that..A × B underflows in floating⁓point arithmetic. |