Periodically adding, changing and deleting file records is called file updating. The correct answer is A.
<span>One system of lens - ocular microscope
Two systems of lens - compound microscope
Some of the parts of a compound microscope are the </span>eyepiece lens.<span> There are two knobs on under the other to one side of the microscope which are used for </span>Coarse focus and Fine focus. There is an illuminator<span> at the bottom of the microscopic stand, which sheds a powerful light on the subject under the lens. Other parts include </span>objective lenses<span>, </span>stage with stage clips<span> (where the subject is placed) and r</span>evolving nosepiece. The tube<span> connects the eyepiece lens to the </span>turret<span>.</span>
According to its structure I'd say that this is SEAL (<span>Software-Optimized Encryption Algorithm). It's difficult to describe how it works, because this kind of ciphers is very tricky. This algorithm uses 160 bit key and it uses 3 tables (R, S, T) to encode and decode.
I'll attach the image where you can see a process of creating a pseudo-random function:
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