Hello,
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Without going for high usage of grammar, let's understand in simple terms. CSE ( computer and electronics engineering) are the one who programmes the thing's and ECE (electronic communication engineering) are the one who make use of the thing.
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If CSE department is manufacturer then ECE department is user. Only after established of a thing by CSE branch, it can be used by ECE branch.
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In means, to make a thing for electronic gadgets, a thing should be firstly programmed which a CSE department will do and the perfect use of the thing will be done by ECE department