Computers in Society Day 4: History of Computing

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

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.

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

Storage Media

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)

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

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

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”).