The Study of Computer Science Chapter 0

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The Study of Computer ScienceChapter 0

• Intro to Computer Science
• CS1510

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Questions

• Syllabus?
• The website?
• The readings?

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Syllabus Review

• What is the minimum percentage that you need to
  earn in order to move on to the next class?
• How many exams will you have this semester?
• When are programming assignments typically due?

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REVIEW What is Computer Science?

• Computer science is a discipline that involves
  the understanding and design of computers and
  computational processes.

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REVIEW A Well-Educated Computer Scientist
Should be Able to...

• Apply the fundamental concepts and techniques of
• computation,
• algorithms, and
• computer design
• to a specific problem

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REVIEW Our Goals

• While a primary goal of this course is to learn
  to program (in Python), our goals include
• increase our problem solving skills
• design good solutions to problems
• test (somehow) how well they are indeed solutions
  to the problem
• provide the solution as a readable document

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But this is HARD!

• I cannot precisely explain why it is hard, only
  that it is indeed hard.
• Your textbook uses an interesting analogy

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An Analogy

• Let us say that you have signed up to study
  French poetry in the original language.
• You have two problems
• You dont speak French
• You dont know much about poetry

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How Does this Apply?

• You have two related problems
• the syntax of French is something you have to
  learn
• the semantics of poetry is something you have
  to learn
• You have two problems you have to solve at the
  same time.

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Programming, Syntax and Semantics

• You have to learn the syntax of a particular
  programming language
• many details about the language, how to debug and
  use it
• You have to learn about problem solving and how
  to put it down on computer.
• There probably is no better way. Its hard!

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But we are getting a bit ahead of ourselves

• We have been talking about programming quite a
  bit
• What is programming?
• The act of translating a sequence of general
  actions to a sequence of specific actions, in a
  specific language, and often for a specific
  computer.
• BUT, before we can get too far with programming
  we have to talk briefly about the computer

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What is a Computer?

• Kind of obvious, but a computer is
  something that does computation.
• A device that performs (high-speed) mathematical
  and/or logical operations or that assembles,
  stores, correlates, or otherwise processes
  information.

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What is a Computer?

• What were the first computers?

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What is a Computer?

• The first computers were people who performed
  difficult calculations by hand, for things like
  ballistic tables.

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What is a Computer?

• Where was the first digital computer built?

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What is a Computer?

• The first modern digital computer was invented
  where?

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Modern Computer Systems

• Consist of two components
• Hardware physical devices required to execute
  algorithms
• Software
• The instructions that tells the computer what to
  do
• Represented as programs in particular programming
  languages

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Modern Computer Systems

• Those parts of the system that you can hit with a
  hammer are called hardware those program
  instructions that you can only curse at are
  called software. - Anonymous

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Hardware

• Most computers consist of
• central processing unit (CPU)
• storage/memory
• input/output (I/O) devices

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CPU Brain of the Computer

• Coordinates all computer operations
• Control Unit
• Reads instructions from memory and decodes and
  executes them using the ALU
• Arithmetic/Logic Unit (ALU)
• Does math and logic calculations on numbers in
  registers

345
Add register A to register B
263
Store the value in register C into memory
location 320843202
608
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Storage/Memory

• Comes with 3 GB of RAM

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Visualizing Memory

• Memory is an ordered sequence of storage
  locations (memory cells)
• Each memory cell has a unique address
• Millions of these cells
• Every memory cell has some contents although the
  contents may not be meaningful.

• X
• 75.62
• STO 005
• ADD 003
• RTV 001
• H
• -26
• 0.005
• 354
• -27.2

999 998 7 6 5 4 3 2 1 0
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Storage/Memory

• The smallest unit of memory is a bit (Binary
  digIT)
• A bit can be off (no voltage) or on (has voltage)
  which we interpret to be 0 or 1
• Memory is organized into 8 bit contiguous groups
  called bytes. A megabyte is 1 million bytes. A
  gigabyte is 1 billion bytes.

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Its All About the Switch

• The basic component of most digital circuitry is
  nothing more complicated than a simple switch.
• A switchs function is pretty obvious, said in a
  number of different ways
• On or Off
• True or False
• 1 or 0

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Electronic Switch

• Early computers used vacuum tubes as switches
• Later, transistors were used as substitutes

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Visualizing Memory

• X
• 75.62
• STO 005
• ADD 003
• RTV 001
• H
• -26
• 0.005
• 354
• -27.2

• Thus, while we might visualize the computer with
  all sorts of data in the memory slots

999 998 7 6 5 4 3 2 1 0
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Visualizing Memory

• It really consists of an arrangement of 1s and
  0s

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Why are there so many types of memory?

• The faster memory is the more it costs
• So we reduce the cost by using small amounts of
  expensive memory (registers, cache, and RAM) and
  large amounts of cheaper memory (disks)
• Why do we need cache?
• Processors are very fast and need quick access to
  lots of data
• Cache provides quick access to data from RAM

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Types of Memory

• Registers
• Very high speed temporary storage areas for use
  in the CPU
• Used for calculations and comparisons
• Cache
• High speed temporary storage for use with the CPU
• Main Memory Random-access Memory (RAM)
• High speed temporary storage
• Contains programs and data currently being used
• Often described in low numbers of Gigabytes (GB)
• Secondary Memory - Disks
• Contains programs and data not currently being
  used
• Often described in Gigabytes (GB) or even
  Terabytes (TB)

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Input/Output Devices

• Allow for human/computer interaction
• Input devices include keyboard and mouse
• Output devices include monitor and printer

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Important Announcements

• For Tomorrow
• Meets in Wright 112 or 339 (know your section and
  time!) Make sure you know your CatID credentials
• If you think you have used them but cant
  remember them, get them reset downstairs in room
  36 (you will need a photo ID)
• Bring a USB drive if you have one
• Get the book!