Fei Xu, Ph.D University of Florida Gainesville, FL 32611-6120 email: feixu@cise.ufl.edu

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Fei Xu

TA job :Spring 2005: CDA 3101: Introduction to Computer Organization

FAQ

1. How to understand the operations to keep some bits while removes other bits (into 0/1)?

Think about the operations “and” and “or” in another way. Below gives the and operation’s result.

Please figure out the or operation’s result yourself.

Original mask result

0 0 0

1 0 0

0 1 0

1 1 1

If the mask is 0, the result is always 0 regardless what the original input is. If the mask bit is 1, the original input will be kept.

For example: 1101. If you want to keep the 2^nd and 3^rd bits and let the first and last bits to be 0

Built mask 0110, and 1101,0110. The final result is 0100. That is what you need.