INST 346
Spring 2018
Homework 1

This assignment is due by ELMS before the start of the class session indicated on the syllabus. Show your work, as it may provide an opportunity to receive partial credit.

Consider the specifications of a laptop that you might consider buying:

Processor type: Intel i7-8550U
Processor speed: 4.0 GHz
Word size: 64 bits
Cache: 8 MB
RAM: 16 GB, 2400 MHz access time
Hard drive: 2 TB, 17 ms access time, 35 MB/s transfer rate
Peripherals: External DVD-RW

To simplify calculations, you may assume that 1 megabyte is 1,000,000 (one million) bytes, 1 gigabyte is 1,000,000,000 (one billion) bytes, etc. (or you may use the exact values if you prefer).

Answer the following questions:

1. If you buy some 4.7 GB DVDs, how many would you need to back up a full hard drive to DVDs (assuming no compression)? At 10 cents per DVD, how much would a full backup cost? At 10 minutes per DVD, how long would a full backup take?
   

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   Now let's see how much stuff that hard drive can hold. Assume you have access to the following information for all 315 million people in the United States:

   Name: 40 characters
   Phone Number: 10 characters
   SSN: 9 characters
   taxes owed: one numeric value
   

   Assume that each character is stored in one byte, and that each numeric value is stored in four bytes. Note that all of the values are stored as characters except the taxes owed. As this example illustrates, it is common to store numeric values when planning to perform numeric calculations, and to store characters in other cases (even when those characters are digits rather than letters).

2. Would all of these data fit on the hard drive of the computer described above? If your answer is yes, what fraction of the disk would this fill? If your answer is no, how big a hard drive would you need?
   

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   Now let's see how long it would take to read that much data off the disk. Assume you have a hard drive large enough to store all the data.

3. Suppose you wanted to add up the taxes owed by all 315 million people. Assume that you start a new disk access for each person (the specifications above tell you how long each disk access takes) and that the actual calculations are very very fast compared to the time required to access the disk (i.e., assume that adding up the numbers takes no time at all). How long would it take to access all the data? Could this be done in a second? In a minute? In an hour? In a day? In a month? In a year?
   

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   Now assume instead (just for the sake of comparison) that it was possible to fit all of this data in RAM (regardless of whether or not that is really possible!).

4. How long would it take to access all the data from RAM? The specifications above included the time required for each RAM access. Could this be done in a second? In a minute? In an hour? In a day? In a month? In a year?

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Comparing those results, ...

5. Which is faster, the RAM or the hard disk? How much faster is it? Twice as fast? 10 times as fast? 100 times as fast? ...