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CISC181 Introduction to Computer Science

Dr. McCoy

Lecture 1February 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/cisc181.05s

• First, let’s take a look at the syllabus http://www.cis.udel.edu/~mccoy/courses/cisc181.05s/syllabus.html

2003 Prentice Hall, Inc. All rights reserved.

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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

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1.3 Computer Organization

• Six logical units of computer1. Input unit

• “Receiving” section

• Obtains information from input devices

– Keyboard, mouse, microphone, scanner, networks, …

2. Output unit • “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 computer3. Memory unit

• 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 computer5. Central processing unit (CPU)

• “Administrative” section

• Supervises and coordinates other sections of computer

6. Secondary storage unit • 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

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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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101.6 Machine Languages, Assembly Languages, and High-level

Languages• Three types of computer languages

1. Machine language• 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

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111.6 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 BASEPAYADD OVERPAYSTORE GROSSPAY

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121.6 Machine Languages, Assembly Languages, and High-level

Languages• Three types of computer languages

3. High-level languages • 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

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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

2003 Prentice Hall, Inc. All rights reserved.

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1.14 Basics of a Typical C++ Environment

• C++ systems– Program-development environment

– Language

– C++ Standard Library

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1.14 Basics of a Typical C++ Environment

Phases of C++ Programs:

1. Edit

2. Preprocess

3. Compile

4. Link

5. Load

6. Execute

Loader

PrimaryMemory

Program is created inthe editor and storedon disk.

Preprocessor programprocesses the code.

Loader puts programin memory.

CPU takes eachinstruction andexecutes it, possiblystoring new datavalues as the programexecutes.

CompilerCompiler createsobject code and storesit on disk.

Linker links the objectcode with the libraries,creates a.out andstores it on disk

Editor

Preprocessor

Linker

 CPU

PrimaryMemory

.

.

.

.

.

.

.

.

.

.

.

.

Disk

Disk

Disk

Disk

Disk

2003 Prentice Hall, Inc. All rights reserved.

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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.

Outline18

fig01_02.cpp(1 of 1)

fig01_02.cppoutput (1 of 1)

1 // Fig. 1.2: fig01_02.cpp2 // A first program in C++.3 #include <iostream>4 5 // function main begins program execution6 int main()7 {8 std::cout << "Welcome to C++!\n";9 10 return 0; // indicate that program ended successfully11 12 } // end function main

Welcome to C++!

Single-line comments.

Preprocessor directive to include input/output stream header file <iostream>.

Function main appears exactly once in every C++ program..

Function main returns an integer value.Left brace { begins function body.

Corresponding right brace } ends function body.

Statements end with a semicolon ;.

Name cout belongs to namespace std.

Stream insertion operator.

Keyword return is one of several means to exit function; value 0 indicates program terminated successfully.

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.

Outline21

fig01_04.cpp(1 of 1)

fig01_04.cppoutput (1 of 1)

1 // Fig. 1.4: fig01_04.cpp2 // Printing a line with multiple statements.3 #include <iostream>4 5 // function main begins program execution6 int main()7 {8 std::cout << "Welcome "; 9 std::cout << "to C++!\n";10 11 return 0; // indicate that program ended successfully12 13 } // end function main

Welcome to C++!

Multiple stream insertion statements produce one line of output.

2003 Prentice Hall, Inc.All rights reserved.

Outline22

fig01_05.cpp(1 of 1)

fig01_05.cppoutput (1 of 1)

1 // Fig. 1.5: fig01_05.cpp2 // Printing multiple lines with a single statement3 #include <iostream>4 5 // function main begins program execution6 int main()7 {8 std::cout << "Welcome\nto\n\nC++!\n";9 10 return 0; // indicate that program ended successfully11 12 } // end function main

Welcome

to

 

C++!

Using newline characters to print on multiple lines.