C 프로그래밍 Introduction to this class C

C++ 프로그래밍 Introduction to this class & C++ Howon Kim 2008. 3. 4

About this course… n n Course name : C++ Programming (CP 24106) Objective of this class: § § § Obtaining the basic ideas of object‑oriented programming Understanding C++ as a tool for problem solving Exercising computer programming to a practical level Understanding the basic concepts of software engineering Understanding the basic concepts of data structures 2

About this course… n About me… - n Howon Kim, Ph. D. from POSTECH, Feb. 1999 Joined to PNU from this semester Email: howonkim@gmail. com Phone: 051 -510 -1010, 010 -8540 -6336 Current Major Interests - - Public Key Cryptography (especially, ECC and Pairing) Low power consumed cryptographic techniques (RFID security, sensor network security) Sensor network security issues (Tiny. OS security, secure routing etc. ) Cryptanalysis (with side channel attack) Teaching the CP 24106 class ! 3

About this course… n Prerequisite class - n Textbook - n Walter Savitch, Absolute C++, 3 rd Ed. , Addison Wesley, 2008 References - - n C Programming (미수강 전문과정 학생 선수과목 test 필요) Bjarne Stroustrup, The C++ Programming Languages, 3 rd Ed. , Addison Wesley Liang, Introduction to C++, Prentice Hall, 2007 Class time - Tuesday, Thursday, 13: 00 ~ 14: 00 4

About this course… n Detailed schedule on this class 주 학습내용 범위 1 C++ Basics CH 1 2 Flow of Control CH 2 3 Function Basics CH 3 4 Parameters and Overloading CH 4 5 Arrays CH 5 6 Structures and Classes CH 6 7 Constructors and Other Tools CH 7 8 Midterm Exam 9 Operator Overloading , Friends, and Refrences CH 8 10 Stream Input and Output CH 12 11 Inheritance and OOP CH 14 10 Templates CH 16 11 Exception Handling CH 18 14 STL(Standard Template Library) CH 19 15 Final Exam Term project 수행 5

About this course… n Assessment 항목 점수 출석 5 중간고사 40 기말고사 40 과제물 15 합계 100 6

What Is C and What Is C++? n The C language was developed originally by Bell Laboratories and standardized by the American National Standards Institute (ANSI) in 1989. n In 1990 the International Standards Organization (ISO) adopted the ANSI standard. n C was expanded to include the ability to build object-oriented software, and hence named C++ in the mid 1990 s. n In short, C++ contains all of the C language features and more!

A Brief History of C and C++ n In the early 1970 s at the Bell Laboratories, C was used originally as a programming language for operating systems, including Bell Labs’ UNIX. n For many years the C software supplied with the UNIX operating system was the standard. n As C grew in popularity and computer hardware became more affordable, many versions of the C language were created. n In 1982 an American National Standards Institute committee was formed to create the ANSI standard for the C language.

A Brief History of C and C++ n This standard was adopted in 1989 and ensured that developers of C software used the same rules and procedures. n In 1994 extensions and corrections to the ISO C standard were adopted. n n Extensions to the C language, providing an improved version of C as well as supporting object-oriented programming methodologies, were designed originally by Bjarne Stroustrup of AT&T Bell Labs. These extensions to the C language became known as the C++ language.

A Brief History of C and C++ n In November 1997, after several drafts of the ISO C++ standards, the ANSI committee published the final draft of the language making it an international standard.

How C Was Named n n n To appreciate how C was named, one needs to examine the historical aspects of the language. C is the result of a development process that began in the early 1960 s with ALGOL 60, then Cambridge’s CPL in 1963, Martin Richard’s BCPL in 1967, and Ken Thompson’s B language in 1970 at Bell Labs. Many of C’s principal concepts are based in BCPL, and these concepts influenced the B and C languages.

C/C++ Is a Compiled Language n Create source code. Source code contains the actual lines of C or C++ statements that give the program direction. n Compile the program. A compiler is a computer program that reads n n the source code, and if the code is “grammatically correct, ” the compiler produces machine code The next build step uses a linker, which literally links, or hooks, the machine code and library code together and binds it into an executable file. A C++ program must be compiled and linked on its target machine because the C++ executable file “talks” to the processor directly. Note the changes that must be made. 12

Creating, Compiling, and Running Programs 13

Rules for Programmers n n n Keep you cool (don’t get mad). Work when you are rested (don’t program when you are tired). KISS your software (keep it simple, sweetie). Give help/get help. Study and know the rules for the language (syntax). 14

Rules for Programmers n n Learn the development environment and tools (we’ll concentrate on Visual C++). Understand the problem you are trying to solve. Build and test your software in steps. Save early/save often (back up your computer programming files often). 15

Why Programmers Love C++ n Extended set of data “containers” q q q n Numeric: both whole numbers and numbers with decimal precision Character: text values True/false data type bool in C++ Pointers and References q Variables that “point” or “refer” to other variables 16

Why Programmers Love C++ n Large number of operators q n Operators are symbols that perform certain actions in C++. n The + symbol adds numbers, - subtracts. n The * multiplies numbers. n Basic decision and control structures enable a program to branch to different code statements or loop over statements. C++ uses functions. q A function is a block of code that performs a task for the program. 17

Why Programmers Love C++ n Functions allow the programmer to: q q q organize code and separate tasks logically separate each piece of the program in its own function and place all the functions in a separate library keep the program size from becoming too large and unwieldy 18

Why Programmers Love C++ n Integrated libraries provide useful functions and n Standard Template Library which contains software n classes for mathematics, file input/output, text operations, and other tools. utilities that are built and ready for use by the C++ programmer. The C++ language provides us many classes, and we can write our own classes as well. 19

Object-Oriented Programming - OOP n n n In the old days, programs followed data flow, written line -by-line, and “flowed” from the top to the bottom step by step. This is called structured (or top-down) programming. In OOP, the program is based on real-world things (objects) - designed and built to model how these “real” things interact. A C++ program is not automatically object-oriented. For a program to be object-oriented, it must contain objects. 20

Introduction to C++ n C++ Origins q Low-level languages n q High-level languages n q n Machine, assembly C, C++, ADA, COBOL, FORTRAN Object-Oriented-Programming in C++ Terminology q Programs and functions q Basic Input/Output (I/O) with cin and cout From these slides, I will use the materials form Pearson. 21 Copyright © 2008 Pearson Addison-Wesley. All rights reserved.

Display 1. 1 A Sample C++ Program (1 of 2) 22

Display 1. 1 A Sample C++ Program (2 of 2) 23

C++ Variables n C++ Identifiers q q q n Keywords/reserved words vs. Identifiers Case-sensitivity and validity of identifiers Meaningful names! Variables q q A memory location to store data for a program Must declare all data before use in program 24

Data Types: Display 1. 2 Simple Types (1 of 2) 25

Data Types: Display 1. 2 Simple Types (2 of 2) 26

Assigning Data n Initializing data in declaration statement q Results "undefined" if you don’t! n n int my. Value = 0; Assigning data during execution q Lvalues (left-side) & Rvalues (right-side) n n n Lvalues must be variables Rvalues can be any expression Example: distance = rate * time; Lvalue: "distance" Rvalue: "rate * time" 27

Assigning Data: Shorthand Notations n Display, page 14 28

Data Assignment Rules n Compatibility of Data Assignments q Type mismatches n q int. Var = 2. 99; // 2 is assigned to int. Var! n n q General Rule: Cannot place value of one type into variable of another type Only integer part "fits", so that’s all that goes Called "implicit" or "automatic type conversion" Literals n n 2, 5. 75, "Z", "Hello World" Considered "constants": can’t change in program 29

Literal Data n Literals q Examples: n n n 2 5. 75 "Z" "Hello World" // // Literal constant int double char string Cannot change values during execution Called "literals" because you "literally typed" them in your program! 30

Escape Sequences n "Extend" character set n Backslash, preceding a character Instructs compiler: a special "escape character" is coming q Following character treated as "escape sequence char" q Display 1. 3 next slide q 31

Display 1. 3 Some Escape Sequences (1 of 2) 32

Display 1. 3 Some Escape Sequences (2 of 2) 33

Constants n Naming your constants q Literal constants are "OK", but provide little meaning n n e. g. , seeing 24 in a pgm, tells nothing about what it represents Use named constants instead q Meaningful name to represent data const int NUMBER_OF_STUDENTS = 24; n n n Called a "declared constant" or "named constant" Now use it’s name wherever needed in program Added benefit: changes to value result in one fix 34

Arithmetic Operators: Display 1. 4 Named Constant (1 of 2) n Standard Arithmetic Operators q Precedence rules – standard rules 35

Arithmetic Operators: Display 1. 4 Named Constant (2 of 2) 36

Arithmetic Precision n Precision of Calculations q VERY important consideration! n Expressions in C++ might not evaluate as you’d "expect"! "Highest-order operand" determines type of arithmetic "precision" performed q Common pitfall! q 37

Arithmetic Precision Examples: q 17 / 5 evaluates to 3 in C++! n n q 17. 0 / 5 equals 3. 4 in C++! n n q Both operands are integers Integer division is performed! Highest-order operand is "double type" Double "precision" division is performed! int. Var 1 =1, int. Var 2=2; int. Var 1 / int. Var 2; n n Performs integer division! Result: 0! 38

Individual Arithmetic Precision n Calculations done "one-by-one" q 1 / 2 / 3. 0 / 4 performs 3 separate divisions. n n First 1 / 2 equals 0 Then 0 / 3. 0 equals 0. 0 Then 0. 0 / 4 equals 0. 0! So not necessarily sufficient to change just "one operand" in a large expression q Must keep in mind all individual calculations that will be performed during evaluation! 39

Type Casting n Casting for Variables q Can add ". 0" to literals to force precision arithmetic, but what about variables? n q q We can’t use "my. Int. 0"! static_cast<double>int. Var Explicitly "casts" or "converts" int. Var to double type n n Result of conversion is then used Example expression: double. Var = static_cast<double>int. Var 1 / int. Var 2; n Casting forces double-precision division to take place among two integer variables! 40

Type Casting n Two types q Implicit—also called "Automatic" n q Done FOR you, automatically 17 / 5. 5 This expression causes an "implicit type cast" to take place, casting the 17 17. 0 Explicit type conversion n Programmer specifies conversion with cast operator (double)17 / 5. 5 Same expression as above, using explicit cast (double)my. Int / my. Double More typical use; cast operator on variable 41

Shorthand Operators n Increment & Decrement Operators Just short-hand notation q Increment operator, ++ int. Var++; is equivalent to int. Var = int. Var + 1; q Decrement operator, -int. Var--; is equivalent to int. Var = int. Var – 1; q 42

Shorthand Operators: Two Options n Post-Increment int. Var++ q n Pre-Increment ++int. Var q n n Uses current value of variable, THEN increments it Increments variable first, THEN uses new value "Use" is defined as whatever "context" variable is currently in No difference if "alone" in statement: int. Var++; and ++int. Var; identical result 43

Post-Increment in Action n Post-Increment in Expressions: int n = 2, value. Produced; value. Produced = 2 * (n++); cout << value. Produced << endl; cout << n << endl; q q This code segment produces the output: 4 3 Since post-increment was used 44

Pre-Increment in Action n Now using Pre-increment: int n = 2, value. Produced; value. Produced = 2 * (++n); cout << value. Produced << endl; cout << n << endl; q q This code segment produces the output: 6 3 Because pre-increment was used 45

Console Input/Output n n n I/O objects cin, cout, cerr Defined in the C++ library called <iostream> Must have these lines (called preprocessor directives) near start of file: q q #include <iostream> using namespace std; Tells C++ to use appropriate library so we can use the I/O objects cin, cout, cerr 46

Console Output n What can be outputted? q Any data can be outputted to display screen n n q n Variables Constants Literals Expressions (which can include all of above) cout << number. Of. Games << " games played. "; 2 values are outputted: "value" of variable number. Of. Games, literal string " games played. " Cascading: multiple values in one cout 47

Separating Lines of Output n New lines in output q Recall: "n" is escape sequence for the char "newline" n A second method: object endl n Examples: cout << "Hello Worldn"; n Sends string "Hello World" to display, & escape sequence "n", skipping to next line cout << "Hello World" << endl; n Same result as above 48

Formatting Output n Formatting numeric values for output q Values may not display as you’d expect! cout << "The price is $" << price << endl; n If price (declared double) has value 78. 5, you might get: n n n The price is $78. 500000 The price is $78. 5 or: We must explicitly tell C++ how to output numbers in our programs! 49

Formatting Numbers n n "Magic Formula" to force decimal sizes: cout. setf(ios: : fixed); cout. setf(ios: : showpoint); cout. precision(2); These stmts force all future cout’ed values: q q To have exactly two digits after the decimal place Example: cout << "The price is $" << price << endl; n n Now results in the following: The price is $78. 50 Can modify precision "as you go" as well! 50

Error Output n Output with cerr works same as cout q Provides mechanism for distinguishing between regular output and error output q n Re-direct output streams q Most systems allow cout and cerr to be "redirected" to other devices n e. g. , line printer, output file, error console, etc. 51

Input Using cin n cin for input, cout for output n Differences: q ">>" (extraction operator) points opposite n q q Object name "cin" used instead of "cout" No literals allowed for cin n n Think of it as "pointing toward where the data goes" Must input "to a variable" cin >> num; q q Waits on-screen for keyboard entry Value entered at keyboard is "assigned" to num 52

Prompting for Input: cin and cout n Always "prompt" user for input cout << "Enter number of dragons: "; cin >> num. Of. Dragons; q Note no "n" in cout. Prompt "waits" on same line for keyboard input as follows: Enter number of dragons: ____ n n Underscore above denotes where keyboard entry is made Every cin should have cout prompt q Maximizes user-friendly input/output 53

Program Style n Bottom-line: Make programs easy to read and modify n Comments, two methods: q q q n // Two slashes indicate entire line is to be ignored /*Delimiters indicates everything between is ignored*/ Both methods commonly used Identifier naming q q q ALL_CAPS for constants lower. To. Upper for variables Most important: MEANINGFUL NAMES! 54

Libraries n C++ Standard Libraries n #include <Library_Name> Directive to "add" contents of library file to your program q Called "preprocessor directive" q n n Executes before compiler, and simply "copies" library file into your program file C++ has many libraries q Input/output, math, strings, etc. 55

Namespaces • Namespaces defined: – • For now: interested in namespace "std" – • Collection of name definitions Has all standard library definitions we need Examples: #include <iostream> using namespace std; • • Includes entire standard library of name definitions #include <iostream>using std: : cin; using std: : cout; • Can specify just the objects we want 56

Summary 1 n C++ is case-sensitive n Use meaningful names q n Variables must be declared before use q n Should also be initialized Use care in numeric manipulation q n For variables and constants Precision, parentheses, order of operations #include C++ libraries as needed 57

Summary 2 n Object cout q n Object cin q n Used for console input Object cerr q n Used for console output Used for error messages Use comments to aid understanding of your program q Do not overcomment 58

Q&A 59

Reference [1] Walter Savitch, Absolute C++, 3 rd Ed. , Addison Wesley, 2008 [2] Liang, Introduction to C++, Prentice Hall, 2007 [3] Barbara Johnston, C++ Programming Today, 2 nd Ed. , Prentice Hall, 2007 60