01:198:170 Chapter Notes - Chapter 1: United States Census Bureau, Walter Houser Brattain, Herman Hollerith
16 May 2018
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Chapter 1: Defining Information Technology
Digitizing Information
●"Digital Information" is data represented using numbers
○Ex: ISBN for a book
○Representing info as numbers not break through, getting a machine to read digital info
was the breakthrough
●Herman Hollerith credited with the first "production" application of digital info
○Worked for US Census Bureau and processing census data by hand was slow, so he
invented a machine to tabulate data based on holes punched in cards
○Punch cards were the primary digital technology for 75 yrs
Stored-Program Computers
All Hardware All the Time HARDWARE
●Tabulating machines were electro-mechanical devices. They are all hardware built out of:
○Wires
○Rollers
○Motors
●So, to change the operations that the machine performed required it to be rewired
Put the Program in Memory SOFTWARE
●Electronic computer solved "rewiring" problem: Central Processing Unit (CPU)!!, which performs
instructions stored in the computer's memory
●Changed instructions from "hard" (wires) to "soft" (memory bits)
●Advantages of soft instructions:
○Programs can be changed rapidly by loading new instructions into the memory
■Feature we use every time we double click or tap on an app
○Programs can be much more complex. Only being limited by size of the memory
●CPU defining property of a "digital computer"
Big and Expensive
●Main problems with early computers is BIG and EXPENSIVE
Burned Out
●Another problem: lack of reliability
●Electronic circuits were built from vacuum tubes which were reasonably reliable for most
applications but the complexity of an instruction-executing CPU required a lot of them to work
at once. Chances were one or more of the tubes would fail at power-up or after sustained
computation, causing computer to crash
●But despite challenges, electronic computer became a powerful game changing tool bc of
transistors
The Switch to Transistors
●John Bardeen, Walter Brattain, Willian Shockley invented semiconductor transistor
●Transistors solved many of the toughest problems facing computer engineers when they used
vacuum tubes
○Transistors are:
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