Transcript Chapter 1 – Introduction to Computers and C++ Programming

CISC181 Introduction to
Computer Science
Dr. McCoy
Lecture 1
February 8, 2005
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What is this course about?
• Basic principles of computer science
• Programming Course using C++
• What does good programming involve?
– Software engineering, structured
programming, object oriented design
– Planning
– Writing clear, well documented, and well
formatted code
– Clear modularity – clear sections of code
doing their job
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What is this course about (cont.)?
• Understanding various tools (data
structures, and computer programs) for
doing the job
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Course Syllabus
• This course has a web page
http://www.cis.udel.edu/~mccoy/courses/ci
sc181.05s
• First, let’s take a look at the syllabus
http://www.cis.udel.edu/~mccoy/courses/ci
sc181.05s/syllabus.html
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1.2
What is a Computer?
• Computer
– Device capable of performing computations and making
logical decisions
• Computer programs
– Sets of instructions that control computer’s processing of
data
• Hardware
– Various devices comprising computer
• Keyboard, screen, mouse, disks, memory, CD-ROM,
processing units, …
• Software
– Programs that run on computer
 2003 Prentice Hall, Inc. All rights reserved.
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1.3 Computer Organization
•
Six logical units of computer
1. Input unit
•
•
“Receiving” section
Obtains information from input devices
– Keyboard, mouse, microphone, scanner, networks, …
2. Output unit
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“Shipping” section
Takes information processed by computer
Places information on output devices
– Screen, printer, networks, …
– Information used to control other devices
 2003 Prentice Hall, Inc. All rights reserved.
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1.3 Computer Organization
•
Six logical units of computer
3. Memory unit
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•
•
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Rapid access, relatively low capacity “warehouse” section
Retains information from input unit
– Immediately available for processing
Retains processed information
– Until placed on output devices
Memory, primary memory
4. Arithmetic and logic unit (ALU)
•
•
“Manufacturing” section
Performs arithmetic calculations and logic decisions
 2003 Prentice Hall, Inc. All rights reserved.
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1.3 Computer Organization
•
Six logical units of computer
5. Central processing unit (CPU)
•
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“Administrative” section
Supervises and coordinates other sections of computer
6. Secondary storage unit
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Long-term, high-capacity “warehouse” section
Storage
– Inactive programs or data
Secondary storage devices
– Disks
Longer to access than primary memory
Less expensive per unit than primary memory
 2003 Prentice Hall, Inc. All rights reserved.
Computer Programming
Languages
• Programmers write programs/instructions
in various programming languages – some
easier for the computer to understand and
some easier for the programmer to
understand.
– Machine languages
– Assembly languages
– High-level languages
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1.6 Machine Languages, Assembly
Languages, and High-level Languages
•
Three types of computer languages
1. Machine language
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•
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Only language computer directly understands
“Natural language” of computer
Defined by hardware design
– Machine-dependent
Generally consist of strings of numbers
– Ultimately 0s and 1s
Instruct computers to perform elementary operations
– One at a time
Cumbersome for humans
Example:
+1300042774
+1400593419
+1200274027
 2003 Prentice Hall, Inc. All rights reserved.
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1.6 Machine Languages, Assembly
Languages, and High-level Languages
•
Three types of computer languages
2. Assembly language
•
•
•
•
English-like abbreviations representing elementary computer
operations
Clearer to humans
Incomprehensible to computers
– Translator programs (assemblers)
• Convert to machine language
Example:
LOAD BASEPAY
ADD
OVERPAY
STORE GROSSPAY
 2003 Prentice Hall, Inc. All rights reserved.
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1.6 Machine Languages, Assembly
Languages, and High-level Languages
•
Three types of computer languages
3. High-level languages
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•
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Similar to everyday English, use common mathematical
notations
Single statements accomplish substantial tasks
– Assembly language requires many instructions to
accomplish simple tasks
Translator programs (compilers)
– Convert to machine language
Interpreter programs
– Directly execute high-level language programs
Example:
grossPay = basePay + overTimePay
 2003 Prentice Hall, Inc. All rights reserved.
Background on C++
• One of the most popular software
development languages
• Superset of the C language (with object
oriented features)
• Be Careful!
– Does not enforce structured style (e.g., array
out of bounds not checked)
– Gives a lot of control to the programmer
(enough rope to…)
– Programmer must be responsible for
enforcing discipline
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1.14 Basics of a Typical C++ Environment
• C++ systems
– Program-development environment
– Language
– C++ Standard Library
 2003 Prentice Hall, Inc. All rights reserved.
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1.14 Basics of a Typical C++ Environment
Phases of C++ Programs:
1. Edit
2. Preprocess
Editor
Preprocessor
Compiler
Linker
3. Compile
Disk
Program is created in
the editor and stored
on disk.
Disk
Preprocessor program
processes the code.
Disk
Compiler creates
object code and stores
it on disk.
Disk
Primary
Memory
4. Link
Loader
5. Load
Disk
6. Execute
Loader puts program
in memory.
..
..
..
Primary
Memory
CPU
..
..
..
 2003 Prentice Hall, Inc. All rights reserved.
Linker links the object
code with the libraries,
creates a.out and
stores it on disk
CPU takes each
instruction and
executes it, possibly
storing new data
values as the program
executes.
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1.20 Introduction to C++ Programming
• C++ language
– Facilitates structured and disciplined approach to computer
program design
• Following several examples
– Illustrate many important features of C++
– Each analyzed one statement at a time
• Structured programming
• Object-oriented programming
 2003 Prentice Hall, Inc. All rights reserved.
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1.21 A Simple Program:
Printing a Line of Text
• Comments
–
–
–
–
Document programs
Improve program readability
Ignored by compiler
Single-line comment
• Begin with //
• Preprocessor directives
– Processed by preprocessor before compiling
– Begin with #
 2003 Prentice Hall, Inc. All rights reserved.
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// Fig. 1.2: fig01_02.cpp
// A first program in C++.
Function main
#include <iostream>
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Single-line comments.
Outline
returns an
directive to
integer
value.
Left brace
{ begins Preprocessor
function
fig01_02.cpp
include
input/output Statements
stream
begins
execution
Function
main appears
body. program
end with a(1 of 1)
header
file <iostream>.
exactly once
in every
C++ semicolon ;.
program..
fig01_02.cpp
// function main
int main()
{
std::cout << "Welcome to C++!\n";
return 0;
//
} // end function
Welcome to C++!
Corresponding right brace }
indicate
thatbody.
program ended successfully
ends
function
Stream
insertion
Name cout
belongs
to operator.
main namespace std.
Keyword return is one of
several means to exit
function; value 0 indicates
program terminated
successfully.
output (1 of 1)
 2003 Prentice Hall, Inc.
All rights reserved.
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1.21 A Simple Program:
Printing a Line of Text
• Standard output stream object
– std::cout
– “Connected” to screen
– <<
• Stream insertion operator
• Value to right (right operand) inserted into output stream
• Namespace
– std:: specifies using name that belongs to “namespace”
std
– std:: removed through use of using statements
• Escape characters
– \
– Indicates “special” character output
 2003 Prentice Hall, Inc. All rights reserved.
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1.21 A Simple Program:
Printing a Line of Text
Escape Sequence
Description
\n
Newline. Position the screen cursor to the
beginning of the next line.
\t
Horizontal tab. Move the screen cursor to the next
tab stop.
\r
Carriage return. Position the screen cursor to the
beginning of the current line; do not advance to the
next line.
\a
Alert. Sound the system bell.
\\
Backslash. Used to print a backslash character.
\"
Double quote. Used to print a double quote
character.
 2003 Prentice Hall, Inc. All rights reserved.
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// Fig. 1.4: fig01_04.cpp
// Printing a line with multiple statements.
#include <iostream>
// function main begins program execution
int main()
{
std::cout << "Welcome ";
std::cout << "to C++!\n";
return 0;
Outline
Multiple stream insertion
statements produce one line
of output.
fig01_04.cpp
(1 of 1)
fig01_04.cpp
output (1 of 1)
// indicate that program ended successfully
} // end function main
Welcome to C++!
 2003 Prentice Hall, Inc.
All rights reserved.
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// Fig. 1.5: fig01_05.cpp
// Printing multiple lines with a single statement
#include <iostream>
// function main begins program execution Using newline characters
print on multiple lines.
int main()
{
std::cout << "Welcome\nto\n\nC++!\n";
return 0;
Outline
to
fig01_05.cpp
(1 of 1)
fig01_05.cpp
output (1 of 1)
// indicate that program ended successfully
} // end function main
Welcome
to
C++!
 2003 Prentice Hall, Inc.
All rights reserved.