The greater threat to computer is a computer virus,a program that causes a computer system to behave in unexpected and undesirable ways.Some signs of a virus include inexplicable loss of free memory,unusually long times for program loading or execution,changes in file or program size,print routines that stop working ,computers”freezing up”‘strange beeps or messages,computer reboot in the middle of a process,and corrupted files.When a virus is executed,it makes copies of itself and spreads from one system to another through network and diskettes.
CAD has the following advantage over traditional method of design-
(i) Computer aided design (CAD) is faster and more accurate results than conventional methods.
(ii) Developing the design of component and associated drafting is a very easy task with CAD.
(iii) Manipulation of various dimensions,attributes and distance of drawing elements,is very easy.This make CAD the most useful designing tool.
(iv) By using CAD it is not necessary to redraw any design or part of it,for further usage.A component once designed,can be copied anywhere for further references.
(v) Various geometric properties including dimensions of various components,their tolerance and interference with each other can be checked accurately,without making their models and prototypes.
(vi) By specifying the material used and the atmospheric working conditions for the component which has to be designed its behavior can be analysed by using CAD.
(vii) Kinematic feature of CAD packages enables the designer to visualize the operational performance of the component.
(viii) Several professional CAD packages also have 3D visualization capabilities,this helps the designer to see their product from different orientations.
(ix) Two or more design can be compared analytically.
(x) Drawing are stored in a systematic manner,which allow their easy and fast retrieval.
Thus use of CAD system provide better engineering drawings,more standardization of drawings,better documentation,fewer design error and greater legibility.