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Understanding the Virus Threat
Published in Steven F. Blanding, Enterprise Operations Management, 2020
A logic bomb is a program that remains dormant until triggered by some extended event, such as the execution of a valid program. A worm is a program that replicates itself in a nondestructive manner, simply eating away at disk space or memory, or both, until the user’s ability to perform productive operations is adversely affected. In fact, the Internet Morris virus was actually a worm. The last category of attack software is the trojan, named after the large, hollow wooden horse that housed Greek soldiers and entered the walls of Troy. The trojan is a program that functions as a delivery vehicle for typically destructive codes. One common method for creating a trojan uses the name of a Disk Operating System executable program file, but uses the extension .COM instead of the extension .EXE. When DOS encounters two files with the same names, but with the extensions .COM and .EXE, DOS attempts to load and execute the file with the extension .COM. A .COM file contains an exact image of how a file appears in memory and is faster to load and more compact than an .EXE file. However, a .COM file is restricted to 64K bytes and can freeze the computer.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
The first commercial operating system, IBM VM/370, was developed in 1968. The first operating system to operate in a wide variety of hardware platforms was Unix, introduced by AT&T Bell Laboratories in the mid-1970s as a computing platform for research and development of engineering applications [Earhart, 1986]. Unix adopted the multitasking operating system technology, by which users may have several different kinds of concurrent activities to make better use of time and resources while getting work done. The size of Unix was small, and thus it could operate in inexpensive computers used for small groups of people. The first operating system to be used massively was MS-DOS, introduced by Microsoft in the early 1980s as a computing platform for personal or individual use [Microsoft, 1986].
MS-DOS for IBM PCs
Published in Paul W. Ross, The Handbook of Software for Engineers and Scientists, 2018
Conceptually similar in some ways to the now obsolete CP/M operating system, MS-DOS borrows concepts from the UNIX operating system. Although MS-DOS was originally designed to have the same general feel as CP/M, it was equipped with some important improvements. MS-DOS is a single-user, single-tasking operating system. Because MS-DOS runs on many different brands of computers, it is not classified as a proprietary operating system. It is, however, limited to the Intel 80x86 family of microprocessors. For this reason, MS-DOS is not a fully generic operating system either. Nevertheless, because of the continuing popularity and large installed base of IBM-compatible microcomputers, MS-DOS will remain a widely used operating system for some time.
Enhancing the accuracy of retrieving quantities of turbidity and total suspended solids using Landsat-8-based-principal component analysis technique
Published in Journal of Spatial Science, 2021
6S,ATCOR, and FLAASH algorithms prerequisite a prior knowledge about several atmospheric parameters, such as visibility, aerosol optical depth, water vapour, ozone, solar zenith and azimuth angles, etc., coinciding with the satellite overpass. The main drawback of using DOS, which is considered as an image-based algorithm, is the disregard of atmospheric conditions, which were there during image acquisition. MAIAC and Sen2Cor are both considered as local algorithms because they have been designed/developed to correct Moderate Resolution Imaging Spectroradiometer (MODIS) and Sentinel-2 imagery, respectively. Therefore, the use of an effective atmospheric correction algorithm is highly demanded to determine/measure the actual reflectance values for different surfaces. In this context, the Landsat-8 surface reflectance data (i.e. Level 2 product), which are generated from the USGS Landsat-8 surface reflectance algorithm, were used in this research.