1. Computers in Society Day 4: History of Computing

2. Information Storage Storing information is as important as processing it. This all started with written language: Important ideas: Precise relationship between spoken and written languages Ability to make a “perfect copy” of a document A medium (clay, paper, …) is used to preserve information over time

3. Organizing Information Given a large collection of information, how do we find what we need? Alphabetical ordering Dewey Decimal System Indices Long before google, people needed to find things in information collections.

4. Mechanical Access A large information repository is much more useful if it can be accessed quickly via mechanical means. Punch cards predate computers (by a long shot!) and were used to store and process large volumes of information. A key insight was that alphabetic information can be processed as if it is numeric Herman Hollerith patented a system in which needles sensed the presence or absence of holes in a card. This converted information into electric impulses. His machine was used for the 1890 census

5. Storage Media

6. Assessing Storage Technology Read/write or read-only Latency (time it takes to find what you want) (time) Transfer rate (how fast you get the information) (bits / second) Capacity (bits) Cost / bit ($) Error rate (errors / bit) Durability (time)

7. An Aside Measuring the size of information: * A bit = 0/1 = a single piece of information * A byte = 8 bits = 1 alphabet character * Megabyte = 1,000,000 bytes * Gigabyte = 1,000,000,000 bytes * Terabyte = 1,000,000,000,000 bytes

8. Back in the day … When I was starting out in the computer biz, an RK05 was “seriously cool”: Data Transfer Rate: 0.1 MBsecond Latency: 70mS Capacity: 2 megabytes Cost: $8000 (1074) (about 1/5 of a house) Media: $99 / disk

9. Organizing Information The organization of information is no longer mechanical – it’s now done with software. A program that manages larges collections of data and finds things for you is a “database”. (Or maybe “google”).