**Professor Simonson**

**How Computers Work**

**CSC 195**

## Quiz 3 - 10 points

This is due by Tuesday, midnight April 25. You should
hand in your drawings directly to the TA, or submit a scanned or
digital version to the dropbox.

1. (2 points) You are designing a machine language that has 50
commands (op codes), 6 address modes, and where each instruction
is stored in 32 bits. How many bits can be used for memory
(parameter) references? How far away can a memory value be
from an instruction that references it? (Recall that the data
might be located forward or backward from the current line)

2. (8 points) Draw a formula and a circuit to implement the full
adder we discussed in class. Recall that this circuit has three
inputs and two outputs. How many gates are in your
circuit? If each gate takes 0.1 nanosecond (1 ten billionth
of a second) for electricity to get through, how long does it take
for a full-32-bit ripple-carry-adder to send out its answer and
carry? Calculate carefully. (Recall that a 32-bit ripple
carry adder is built out of 32 full adders.)

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shai@stonehill.edu