[CSE10200] Programming Basis

(프로그래밍 기초)

Chapter 2

Seungkyu Lee

Assistant Professor, Dept. of Computer Engineering

Kyung Hee University

Chapter 2

Introduction to the C++ Language

Figure 2-1 Taxonomy of the C++ language

Structure of a C++ program

Pre-compiler directive

Opening brace

Closing brace

Opening brace

Closing brace

Structure of a C++ Program

Preprocessor Directives

#include “I want to use a predefined library

called iostream”

Always start with a ‘#’

iostream: a library for inputs (from

e.g., a user) and outputs (to e.g.,

the monitor)

Without namespace

Hello World!

Namespace std contains

all the classes, objects

and functions of the

standard C++ library.

#include

int main ()

{

std::cout

main function

int main() • The main body of my program.

• Compiler first tries to locate “main()” to find where to begin the program

• This is a function

Comment

• Internal program document

• Not considered as a program code

Start of comment

End of comment

Start of comment

End of comment

Nested Block Comments are Invalid

Identifiers

Memory

Address of memory:

Hard to remember

Identifier: name of

address

Identifiers

Memory

studentID

studentGrade1

studentGrade2

Identifiers

Identifiers

Memory

studentID

studentGrade

studentName

Compiler keeps track

of [identifier-address]

table

Naming Identifiers

• Allowed characters: A-Z, a-z, 0-9, _ (underscore)

• Not allowed to start with a digit. E.g., 3class (x), class3(o)

• The identifier cannot duplicate a reserved word. e.g., if, case, while…

• Good names descriptive but short

• C++ is case sensitive; PI, Pi and pi are different.

Standard Data Types

Integer and Floating Types

2 or 4 Bytes

4 Bytes

2 Bytes

8 Bytes

10 Bytes

4 Bytes

Size of value type depends on computer architecture

Max/Min of Integer Value Type

Type Sign Byte Minimum value Maximum value

short int/short signed

2 -32,768 32,767

unsigned 0 65,535

int (PC) signed

2 -32,768 32,767

unsigned 0 65,535

int (Mainframe) signed

4 -2,147,483,648 2,147,483,647

unsigned 0 4,294,967,295

long int/long signed

4 -2,147,483,648 2,147,483,647

unsigned 0 4,294,967,295

Maximum/Minimum of C++ data types

In C++ the Boolean constants are true

and false. Additionally, following

traditional standards, any nonzero

number is considered true, and zero is

considered false.

Note:

Variables

• Variable = Identifier + Type

Variables Declaration

= Identifier & Type assignment

Variable Initialization

• Variable declaration

≠ Variable initialization

• Should be initialized by a programmer before it is used

int count; declaration (o), initialization(x)

char grade = ‘d’; declaration (o), initialization(o)

Constants

• Data values that cannot be changed during program execution

• E.g.,

Integer constant 4

Float constant 3.141592

Character constant ‘d’

Character constant ‘\0’

String constant “Hello word”

The only bool types constants are true,

printed as 1, and false, printed as 0.

Note:

So far ~~ so good ?

Standard streams

• A mapping between data and input/output device

More about cout

• width(int) function sets the width for

printing a value

• Only works until the next insertion command comes

int x = 42;

cout.width(5);

cout

More about cout

• fill(char) function sets the fill

character.

• The character remains as the fill character until set again.

int x = 42;

cout.width(5);

cout.fill(‘*’);

cout

More about cout • precision (int) sets the number of significant

digits of float type numbers

float y = 23.1415;

cout.precision(1);

cout

More about cout • Output Manipulators (not a function)

endl - outputs a new line character, flushes output

dec - sets int output to decimal

hex - sets int output to hexadecimal

oct - sets int output to octal

#include

int x = 42;

cout

Example codes reading (Program 2-2)

• #include

• using namespace std;

• int main (void)

• {

• int a;

• int b;

• int c;

• int sum;

• cout a >> b >> c;

• // Numbers are now stored in a, b, and c. Add them.

• sum = a + b + c;

• cout