Transcript program - Nipissing University Word

COSC1557: Introduction to
Computing
•Haibin Zhu, PhD.
•AssistProfessor
•Department of Computer Science
•Nipissing University
•(C) 2002
Instructor
• Haibin Zhu, Ph. D.
• Assistant Professor, Department of CS and Math,
Nipissing University
• Room: A124A Ext.: 4434
• Email: [email protected]
• URL: http://www.nipissingu.ca/faculty/haibinz
• Office Hour: Mon.–Fri. 2:30pm-4:30pm, and by
appointment
Course Description
• Nature and uses of the computer-,
algorithms-, number systems, information
representation; and organization, with an
overview of computer hardware and
software, computing systems and major
applications. Ethical and societal issues arc
discussed. An introduction to high-level
languages with an emphasis on writing
programs in C++.
Textbook and references
• Textbook: Joel Adams and Larry Nyhoff, C++: An
Introduction to Computing, 3/e. Prentice Hall, ©
2003 ISBN: 0-13-091426-6
• Lecture Notes on
http://cs.calvin.edu/books/c++/intro/3e/PPSlides/
• Student Supplements: CD-Lab Manual (ISBN:
013080648X)
• Some Lab:
http://cs.calvin.edu/books/c++/intro/3e/HandsOnC++/
Beginning Snapshots
Chapter 0
•[email protected]
Objectives
• Give an overview of computer science
– Show its breadth
• Provide context for computer science
concepts
– Events from the past
• Describe basic components, organization
of a computer
Areas of Computer Science
• Algorithms and Data
Structures
• Numerical and Symbolic
Computation
• Architecture
• Operating Systems
• Artificial Intelligence and • Programming
Robotics
Languages
• Database and Information • Software Methodology
Retrieval
and Engineering
• Human-Computer
Communication
• Social and Professional
Context
Important Concepts in Computer
History
• The mechanism of arithmetic
• The stored program
• The graphical user interface
• The computer network
First-Generation Computers
• Vacuum tube computers 1945-1956
– ENIAC
1943-1946
– John Von Neumann's
"First Draft of a Report on
the EDVAC"
1945
– First bug in a computer
1945
– UNIVAC
1951
Second Generation Computers
• Used transistors
1956-1963
• FORTRAN
1957
• IBM 7090
1958
LISP
• COBOL
ALGOL 60
1960
Third-Generation Computers
• Chips and Integrated
Circuits
• The IBM System/360
1964-1971
1964
• The PDP-8
• Douglas Englebart:
the mouse, Two-D display,
editing, hypermedia,
1965
1968
Pascal
• Ken Thompson: UNIX
1969
ARPANET – The beginning of the Internet
Fourth-Generation Computers
• Intel 4004 Chip
1971
• Dennis Richie: C
1973
• Ethernet
• Court rules Atanasoff was legal inventor of first
electronic digital computer
• Altair, BASIC, Apple 1
1974
• Apple II, Cray 1, Apple Corp.
Microsoft Corp.
1976
• IBM PC
1981
Fourth-Generation Computers
• Bjarne Stroustrup: C++
1983
Novell announces Netware
TCP/IP
• Macintosh
1984
• Windows
1985
• Intel 386 Chip
1986
• Tim Berners—Lee: WWW
1991
• Linux
1992
Fourth-Generation Computers
• Pentium chips, Power PC chip
1993
MOSAIC, Apple Newton
• Netscape Navigator 1.0, Yahoo!
Palm computing
1994
• James Gosling: JAVA
Windows 95, Internet Explorer,
Internet goes commercial
1995
• Windows 98, Apple's IMAC
Microsoft's court case
1998
Fourth-Generation Computers
• Y2K Problem, Powermac G4
1999
• Windows 2000
1 GHZ processors
2000
• Mac OS X
Windows XP
2001
• Quantum Computer
2002
Graphical User Interface
• Command line interface required precise
and cryptic commands
• Xerox PARK had developed GUI
prototype in 1972
– Steve Jobs saw it several years later and
used new hardware capabilities to implement
• GUI makes computer easy to use
Network
• Defn: Two or more computers connect to
exchange resources
– Processing power
– Storage
– Access to a printer
– Software resources
– Messages
Network
• Time sharing in early 1960s
– Users communicate with host computer
• ARPANET connected research center computers
in 1969
– Eventually developed into Internet
• Local Area Network hardware and operating
systems developed late 1970s
• ISPs now affordable, widely available for even
home computers
Computer Organization
Hardware and Software
Calvin College
•[email protected]
Computing Systems
Computers have two kinds of components:
• Hardware, consisting of its physical devices
(CPU, memory, bus, storage devices, ...)
• Software, consisting of the programs it has
(Operating system, applications, utilities, ...)
Hardware: CPU
Central Processing Unit (CPU):
– the “brain” of the machine(?)
– location of circuitry that performs arithmetic and
logical ML statements
– measurement: speed (roughly) in megahertz
(millions of clock-ticks per second)
– examples: Intel Pentium(PI, PII, PIII, P4), AMD
K6, Motorola PowerPC, Sun SPARC,
Hardware: RAM
Random Access Memory (RAM)
– “main” memory, which is fast, but volatile...
– analogous to a person’s short-term memory.
– many tiny “on-off” switches: for convenience
• “on” is represented by 1, “off” by 0.
– each switch is called a binary digit, or bit.
• 8 bits is called a byte.
• 210 bytes =1024 bytes is called a kilobyte (1K)
• 220 bytes is called a megabyte (1M).
Hardware (Disk)
Secondary Memory (Disk):
– Stable storage using magnetic or optical media.
– Analogous to a person’s long-term memory.
– Slower to access than RAM.
– Examples:
• floppy disk (measured in kilobytes)
• hard disk (measured in gigabytes (230 bytes))
• CD-ROM (measured in megabytes), ...
Hardware: the Bus
The Bus:
– Connects CPU to other hardware devices.
– Analogous to a person’s spinal cord.
– Speed measured in megahertz (like the CPU),
but typically much slower than the CPU...
– The bottleneck in most of today’s PCs.
Hardware: Cache
While accessing RAM is faster than accessing
secondary memory, it is still quite slow,
relative to the rate at which the CPU runs.
To circumvent this problem, most systems add
a fast cache memory to the CPU, to store
recently used instructions and data.
(Assumption: Since such instructions/data
were needed recently, they will be needed
again in the near future.)
Hardware: Summary
Putting the pieces together:
cache
CPU
Main
Memory
Secondary
Memory
Bus
Programs are stored (long-term) in secondary memory,
and loaded into main memory to run, from which
the CPU retrieves and executes their statements.
Software: OS
The operating system (OS) is loaded from
secondary memory into main memory when
the computer is turned on, and remains in
memory until the computer is turned off.
Cache
Bus
CPU
RAM
OS
Disk
Software: OS
The OS acts as the “manager” of the system,
making sure that each hardware device
interacts smoothly with the others.
It also provides the interface by which the
user interacts with the computer, and awaits
user input if no application is running.
Examples: Windows 2000, Windows XP,
Windows-NT, UNIX, Linux, Solaris, MacOS,
...
Software: Applications
Applications are non-OS programs that
perform some useful task, including
word processors, spreadsheets, databases,
web browsers, C++ compilers, ...
Example C++ compilers/environments:
– CodeWarrior (MacOS, Win95, WinNT, Solaris)
– GNU C++ (UNIX, Linux)
– Turbo/Borland C++ (Win95, WinNT)
– Visual C++ (Win95, WinNT)
Software: User Programs
Programs that are neither OS programs nor
applications are called user programs.
User programs are what you’ll be writing in
this course.
Putting it all together
Programs and applications that are not running are
stored on disk.
Cache
Bus
CPU
RAM
OS
Disk
App
Putting it all together
When you launch a program, the OS controls the CPU
and loads the program from disk to RAM.
OS
Bus
Disk
RAM
OS
App
Cache
CPU
App
Putting it all together
The OS then relinquishes the CPU to the program,
which begins to run.
App
Bus
Disk
RAM
OS
App
Cache
CPU
App
The Fetch-Execute Cycle
As the program runs, it repeatedly fetches the next
instruction (from memory/cache), executes it,
and stores any results back to memory.
App
Disk
RAM
OS
App
Cache
CPU
App
Bus
That’s all a computer does: fetch-execute-store,
millions of times each second!
Programming
What is Programming?
A sequence of statements that instruct a
computer in how to solve a problem is
called a program.
The act of designing, writing and maintaining
a program is called programming.
People who write programs are called
programmers.
What kinds of statements
do computers understand?
A computer only understands
machine language statements.
A machine language statement is a
sequence of ones and zeros that cause
the computer to perform a particular
action, such as add, subtract, multiply, ...
Machine Language (ML)
ML statements are stored in a computer’s
memory, which is a sequence of switches.
For convenience of representation,
an “on” switch is represented by 1,
and an “off” switch is represented by 0.
ML thus appears to be binary (base-2):
0010111010110101
Early Computers
... required a programmer to write in ML...
– Easy to make mistakes!
– Such mistakes are hard to find!
– Not portable -- only runs on one kind of
machine!
Programming was very difficult!
A Bright Idea
Devise a set of abbreviations (mnemonics)
corresponding to the ML statements, plus a
program to translate them into ML.
ADD
Assembler
0010111010110101
The abbreviations are an assembly language,
and the program is called an assembler.
Assembly Languages
Allowed a programmer to use mnemonics,
which were more natural than binary.
+ Much easier to read programs
+ Much easier to find and fix mistakes
– Still not portable to different machines
High Level Languages
Devise a set of statements that are close to
human language (if, while, do, ...),
plus a program to translate them into ML.
The set of statements is called a high level
language (HLL) and the program is called
a compiler.
HLL Compilers
Where an assembler translates one mnemonic
into one ML statement,
a HLL compiler translates one HLL statement
into multiple ML statements.
z = x + y;
Compiler
1010110011110101
0000000000010000
0010111010110101
0000000000010010
0010111011111101
0000000000010100
HLLs
High level languages (like C++) are
+ Much easier to read programs
+ Much easier to find and fix mistakes
+ Portable from one machine to another
(so
long as they keep to the language standard).
Objectives in Programming
A program should solve a problem:
+ correctly (it actually solves the problem)
+ efficiently (without wasting time or space)
+ readably (understandable by another person)
+ in a user-friendly fashion
(in a way that is easy for its user to use).
Summary
A computer has two kinds of components:
– Hardware: its CPU, RAM, Disk(s), ...
– Software, its OS, Applications, and User Programs.
There are “levels” to computer languages:
– ML consists of “low” level binary statements, that is hard to
read, write, and not portable.
– Assembly uses “medium” level mnemonics: easier to
read/write, but not portable.
– C++ is a “high” level language that is even easier to
read/write, and portable.