Transcript Introduction to Computers and Terminology

Introduction to Computers
and Terminology
CS280 – 09/01/05
Why do we care?
 Communication requires specific language.
 Different fields and activities have different
languages.
 Understanding the language can help you
understand the activity and vice versa.
 Sports, hobbies, majors, businesses, etc. all
have their own languages and these
languages help us to communicate effectively
with others in that same field.
Objectives
At the conclusion of this section you will be able to:
 identify the basic components of a computer system.
 define the difference between volatile and nonvolatile memory
 order different size words used in the computing field
 identify the difference between hardware and
software
 identify the difference between OS software and
application software
 identify common elements of standard user interfaces
 begin to “look under the covers” of your computer
and its applications
Objectives – you will be able to define
the following terms
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Computer
processor
CU
ALU
main memory – RAM
auxilliary storage
volatile vs persistent
hard disk
floppy disk
input device
output device
device driver
boot
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shortcut
menu
command button
control
file type
GUI
WYSIWYG
software, hardware
treeware, wetware
algorithm
program
execute
abstraction
generalization
We will start with what a computer is
Figure 1.1. Examples of the monolithic (a) and
component (b) systems.
a.
b.
Figure 1.9. A componentapproach computer.
Figure 9.2. The principal
components of a computer.
von Neumann architecture – developed by John von Neuman
Figure 1.10. A motherboard.
Central Processing Unit or CPU
 The CPU consists of the ALU and CU.
 The ALU – Arithmetic Logic Unit – processes
operations (adding, subtracting, logical
operations, etc.)
 The CU – Control Unit – controls the flow of
activity, processing one tiny instruction at a
time.
 One action at the user end results in many
instructions in the CU
Storage
 Two storage types
 Volatile – Main memory – temporary storage. If
machine is turned off, main memory is lost.
 RAM/ROM
 Non-volatile – Auxiliary storage. If machine turned off,
the non-volatile memory remains. Hard drive, floppy
disks, tapes, etc.
 RAM
 Sequential
 All memory is composed of binary devices.
Computers are binary machines
 A binary device consists of two states.
 Refer to these states as on or off or high voltage/low voltage.
 Represented as 0 (off) and 1 (on).
 All numbers, characters, instructions, etc are represented as a
series of 1’s and 0’s.
 Bits are grouped into 8-bit segments called bytes.
 Most computers have byte addressability.
 All storage is binary
 We also refer to computers as digital as opposed to analog.
Main memory
 Main memory is volatile storage.
 It retains its values only while there is power
to the machine.
 When power is lost or the machine is shut
down, the memory is wiped clean.
 Think of it as the computer’s desktop. We
can work on the items only while they are on
the desk. When we leave, we move them
into permanent storage, since they are
vulnerable to loss if they remain.
Main memory consists of
 a series of “bits”.
 each can have one of two values – on or off.
 On is interpreted as a 1 and off is interpreted
as the value 0.
 All data is represented as some sequence of
0’s and 1’s on a modern digital computer.
Figure 1.11. Sequential versus
random storage access.
Main memory is accessed randomly
 That means that each location can be
accessed independently of all others.
 Think of the library. You don’t have to go
through all of the books to find one. You go
to an index and then can go rapidly to the
section then the book you are interested in.
 Random access is this kind of access
method.
CPU and main memory
 The processor of the computer works with
main memory.
 Anything that the processor is going to
operate on has to be in memory.
 Anything that comes in or out must go
through main memory.
 It is like your desktop. What is on top can be
worked on. What is sitting in a file cannot be.
Addressability
 Memory is a
collection of cells,
each with a unique
physical address.
Most machines are
8-bit…a cell consists
of one byte.
From Dale
Auxiliary Storage
(“Permanent” Storage)
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Hard drives
Floppy drives
Memory sticks (USB devices)
tape
These are all also input/output devices – we can read
from and write to.
Some CD/DVD are only input, others are input/output.
We describe the size of the storage in terms of bytes.
Or in other words how many 8 bit locations are on
that medium.
Sizes in Perspective
Page 119
Figure 1.12. A hard disk.
Magnetic Disks
 A read/write head travels across a spinning magnetic
disk, retrieving or recording data
Figure 5.5
The organization
of a magnetic disk
Internal drives and external storage
 Floppy disks share the same basic
mechanism as the hard drive.
 Only one platter.
Magnetic Tape
 The first truly mass
auxiliary storage
device was the
magnetic tape drive
Figure 5.4 A magnetic tape
Compact Disks
 A CD drive uses a laser to read information
stored optically on a plastic disk
 CD-ROM is Read-Only Memory
 DVD stands for Digital Versatile Disk
Other parts of the computer system
 Input devices – mouse, keyboard , camera,
scanner – converts analog (real world) to
binary representation (or digital).
 Output devices – printer, display – converts
binary back to something we can deal with.
Connections
 The parts are connected to one another by a
collection of wires called a bus
Figure 5.2 Data flow through a von Neumann architecture
Beyond the hardware
Computing Systems (Cont’d)
Hardware: The physical elements of a
computing system (printer, circuit boards,
wires, keyboard…)
Software: The programs that provide the
instructions for a computer to execute
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One other component
 Wetware – The human user. A computer
system needs the human being to get things
started, provide input, interpret output, etc.
Hardware vs Software
 Hardware is the “hard stuff”. All of the
electronics and peripherals are hardware.
 Software is the stuff that we cannot touch.
 Software is the instructions that the computer
executes and the data on which it operates.
Software vs data
 We might have an application such as Word.
 The application does the activity for us.
 The data are the words, formatting
instructions, special characters that make up
the document.
 Data can also be provided to the application
via the keyboard or the mouse.
Kinds of software
 Operating system
 Examples are Windows, Linux, Mac OS
 Each provides similar services
 Each provides the tools that allow a user to interact
with the hardware without having to deal with the
detail. (see Abstraction).
 Applications
 System tools (used by programmers)
 User tools (used by humans)
 Examples are Word, PeopleSoft, Myst, editors,
compilers
Operating systems
 Provide a layer between the user applications
and the hardware.
 Manage the processes. Keeps track of which
processes are active and in what order
requests for services are processed.
 Keeps track of the various storage
locations…main memory, auxilliary storage,
etc.
Application software
 Early applications were very specific. If I had
to write a report, I had a program to do so.
 Examples are e-campus and Blackboard.
 More recently, generic user tools came into
being. The use that the user will put to the
tool is determined by what they want to do,
not what the programmer designed into it.
 Examples are the general purpose tools of
word and excel.
Computing as a Tool
Programmer / User
Systems Programmer
(builds tools)
Applications Programmer
(uses tools)
Domain-Specific Programs
User with No
Computer Background
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User interfaces
 User interface – What the user sees and
“interacts” with.
 It is the virtual image of what the user is trying
to do.
 When I type on the keyboard, I usually see an
echo of what I am typing. But it looks like I
am directly typing onto the screen.
Good interfaces
 Intuitive
 Consistent across applications
 Aesthetic
 Useful
 Let’s look at some examples
WYSIWYG
 Acronym for What You See Is What You Get
 Word uses a WYSIWYG interface.
 See HTML document for a non-WYSIWYG
interface (and an example where a generic
editor is used to write code intended to be run
under another application)
Interface features
 Control buttons
 Sliders
 Minimize, maximize, and variable size
 Menus – expected functionality