Memory

• Define the way memory is measured in a computer.
• Describe the typical size of various files.
• Describe your options for storing data for this class.

• Why do we measure things?
  • What are some things we measure?
  • Why?
• How do we measure things?
  • There is generally a "unit", sometimes more.
  • There is generally a conversion between units.
  • How do we measure liquids in the US?
    • Look at wikipedia
    • How many cups in a gallon?
      • Let's build a simple spread sheet.
      • 
• Many measurements are somewhat arbitrary.
  • For example inches, feet, ells and others were based on human body proportions.
• For computing we use a system based on binary digits.
  • Binary is the base 2 number system.
  • The only digits in this system are 0 and 1.
• A bit is a BInary digiT, and represents one very small piece of information.
  • Think state of a light switch.
  • Network bandwidth is measured in bits.
  • Processor "word" sizes are measured in bits.
• The next unit is a byte and 8 bits = 1 byte.
  • Files are measured in bytes.
• At some time most of the world got tired of difficult conversions.
  • How many feet in an mile?
  • So measurements were standardized.
  • And new units were "derived" using the SI Prefix System
• In memory we sort of do the same thing.
  • A kilo is 10³ or 1000
    • So a kilobit (kb) is 1000 bits.
    • And a kilobyte (kB) is 1000 bits.
  • Very little is measured in kB any longer
    • Really just file sizes.
• Something a bit confusing
  • For technical reasons, hardware memory is usually based on a power of 2.
  • For the longest time a kb was 2¹⁰ or 1024 bits.
    • But this is confusing to many people.
    • 2¹⁰ bits is not called a kibibit.
  • It doesn't really matter much, and referring to 1024 bits as a kilobit is not a major problem.
  • But it is not right either.
  • For example, here is news about someone suing Seagate over the definition!
    • Read the first few comments under the article!
  • Use kibibyte correctly and impress your techno-nerd friends.
• For this class you will need a place to store your data.
  • The first thing we should figure out is how much space will you need.
  • I expect that you will generate:
    • 20 or so word documents.
    • 20 or so excel worksheets.
    • 5 or fewer PowerPoint documents.
    • And a number of other files, (pictures, text files ...)
    • So how how big are these files?
      • I found a report from Microsoft discussing this issue.
      • What is wrong with his graph?
      • We could use excel to average his findings.
      • And estimate the total space we need for this class : about 50 MB.
      • 
  • So what are your storage options?
    • Use A USB drive
      • These are low cost storage devices that work almost everywhere
      • This article discusses some of the advantages and disadvantages of this type of drive.
        • I have found people tend to lose/forget them.
        • They have the possibility of being corrupted.
        • They break if you are not careful.
        • But they are convenient, easy and low cost.
    • Use the campus S drive
      • This is available on all campus labs.
      • Somewhat more restricted outside of campus, but one of the questions lets you explore this more.
    • Use cloud storage (Microsoft one drive)
      • I use dropbox but this is less convenient.
  • So do you have enough storage in all places?
    • Convert everything to bytes and divide.
    • Do this on a spreadsheet.
    •