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So I am studying this great book, and Chapter $3.1$ is about registers.

Quoting from this book / chapter:

A register is a storage device that can "store" or "remember" a value over time, implementing the classical storage behaviour $out(t) = out(t-1)$.

What is mean by:

the classical storage behaviour $out(t) = out(t-1)$ ?

If $out(2) = out(1)$ and $out(1) = out(0)$ how are we ever going to store a value?

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Registers can be thought of as collections of flip-flops. These have inputs which, when activated, change the stored value. When not activated, the stored value stays the same. Look at the truth tables in the Wikipedia article.

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    $\begingroup$ Thank you very much for your response. My question is more about "classical storage behaviour out(t) = out(t-1)" actually. Title of my question is not very accurate I believe.. $\endgroup$ Mar 3 '16 at 16:45
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    $\begingroup$ "Classical storage behavior" is what flip-flops implement. The authors of your book tried to convey this information, but clearly failed. Plainly, if it were always true that out(t)=out(t-1), then registers would be constant. The only way out is that this behavior actually doesn't always hold. If you want to see how these things actually work, I encourage you to read the Wikipedia article. $\endgroup$ Mar 3 '16 at 16:50

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