Ch02 C++ Programming Basics

8/6/2019 Ch02 C++ Programming Basics

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Introduction to Programming

Engr. Rashid Farid [email protected]

Chapter 02: C++ Programming Basics

International Islamic University H-10, Islamabad, Pakistan

http://www.iiu.edu.pk


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Basic Program Construction

//first.cpp#include

using namespace std;

int main()

{

cout


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Basic Program Construction Because of the parentheses() the compiler

comes to know that this a function not avariable.

The parentheses arent always empty. Theyre

used to hold function arguments (values passed

from the calling program to the function).

Line number 2 and 3 are not part of the

function.

The word int preceding the function name

indicates that this particular function has a

return value of type int. The bodyof a function is surrounded by braces

(sometimes called curly brackets).


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Basic Program Construction Every function must use this pair of braces

around the function body.

A function body can consist of many statements

but this function has only two statements

(line nunber 6 and 7)

You can put several statements on one line and

one statement in over two or more lines.

cout


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Basic Program Construction We dont recommend these syntax. its

nonstandard and hard to read. but it doescompile correctly.

#include is a preprocessor directive, which

must be written on one line.

A string constant Welcome to this course\n

can also be broken into separate lines if uinsert a backslash (\) at the line break or

divide the string into two separate strings,

each surrounded by quotes

cout


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Basic Program Construction We dont recommend these syntax. its

nonstandard and hard to read. but it doescompile correctly.

#include is a preprocessor directive, which

must be written on one line.

A string constant Welcome to this course\n

can also be broken into separate lines.e.g.

A programs may consists of many functions but

themain() function will be executed first.

If there is no function calledmain() in your

program, an error will be reported when yourun the program.

main() function may also call other functions.


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Program Statements There are two statements this program

cout


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Output usingcoutcout


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Output usingcout

(If you know C, youll recognize


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String Constants The phrase in quotation marks, Welcome to

this course\n, is an example of a stringconstant.

A constant, unlike a variable, cannot be given

a new value as the program runs. Its value is

set when the program is written, and it

retains this value throughout the programsexistence.

The \n character at the end of the string

constant is an example of an escape sequence.

The \n causes the next text output to be

displayed on a new line.

Line no. 2 and 3 in our program are called

directives. The first is apreprocessor

directive,and the second is a using directive.


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Directives Theyre not part of the basic C++ language,

but theyre necessary anyway.Preprocessor Directives

#include

This is not a program statement or a part of a

function body. It starts with a number sign

(#). Its called apreprocessor directive.

Recall thatprogram statements are instruct-

ions to the computer to do something, such as

adding two numbers or printing a sentence.

A preprocessor directive, on the other hand,is an instruction to the compiler. A part of

the compiler called thepreprocessordeals

with these directives before it begins the

real compilation process.


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#include Directive Thepreprocessor directive #include tells the

compiler to insert another file into yoursource file. In effect, the #include directive

is replaced by the contents of the file

indicated.

Using an #include directive to insert another

file into your source file is similar topasting a block of text into a document with

your word processor.

#include is only one of many preprocessor

directives, all of which can be identified by

the initial # sign.

The type file usually included by #include is

called a header file.


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Header Files In our program the preprocessor directive

#include tells the compiler to add the sourcefile IOSTREAM to the FIRST.CPP source file

before compiling.

IOSTREAM is an example of a header file

(sometimes called an include file). Its

concerned with basic input/output operations,and contains declarations that are needed by

the cout identifier and the


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usingDirective A C++ program can be divided into different

namespaces. A namespace is a part of theprogram in which certain names are recognized;

outside of the namespace theyre unknown.

The directive using namespace std; says that

all the program statements that follow are

within the std namespace. Various program components such as cout are

declared within this namespace. If we didnt

use the using directive, we would need to add

the std name to many program elements.e.g.

std::cout


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Comments Comments help the person writing a program,

and anyone else who must read the source file,understand whats going on.

The compiler ignores comments, so they do not

add to the file size or execution time of the

executable program.

Comments start with a double slash symbol (//)and terminate at the end of the line

//first.cpp

#include //preprocessor directive

using namespace std; //using directive

int main() //function name main

{ //start function body

cout


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Other Styles of Comments/* this is an old-style comment */

/* this

is a

potentially

very long

multilinecomment

*/

intmain(/* a comment within parentheses*/)

{ /* this is comment into the function body */ }

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Integer Variable Variables are the most fundamental part of any

language. A variable has a symbolic name andcan be given a variety of values.

Variables are located in particular places in

the computers memory. When a variable is

given a value, that value is actually placed

in the memory space assigned to the variable. Integer variables represent integer numbers

like 1, 30,000, and 27. Such numbers are used

for counting discrete numbers of objects, like

11 pencils or 99 bottles of beer.

integers have no fractional part; you can

express the idea of four using integers, but

not four and one-half.


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Defining an Integer Variable Integer variables exist in several sizes, but

the most commonly used is type int. The amount of memory occupied by the integer

types is system dependent.

On a 32-bit system such as Windows, an int

occupies 4 bytes (which is 32 bits) of memory.

This allows an int to hold numbers in therange from 2,147,483,648 to 2,147,483,647.

The type int occupies 4 bytes on current

Windows computers, it occupied only 2 bytes in

MS-DOS and earlier versions of Windows.


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Figure: A variable of type int in memory


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Defining an Integer Variable// intvars.cpp

// demonstrates integer variables

#include


int main(){

int var1; //define var1

int var2; //define var2

var1 = 20; //assign value to var1

var2 = var1 + 10; //assign value tovar2

cout


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Code Explanation The statements int var1; int var2; define two

variables, var1 and var2 of type integer.

These statements, which are called

declarations, must terminate with a semicolon

You must declare a variable before using it.

However, you can place variable declarationsanywhere in a program. Its not necessary to

declare variables before the first executable

statement (as was necessary in C).

A declaration introduces a variables name

(such as var1) into a program and specifiesits type (such as int).

if a declaration also sets aside memory for

the variable, it is also called a definition.


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Variable Names The statements int var1; int var2; in the

program are definitions, as well as declara-tions, because they set aside memory for var1

and var2.

The program uses variables named var1 and var2

The names given to variables are called

identifiers. You can use upper and lowercaseletters, and the digits from 1 to 9. You can

also use the underscore (_).

The first character must be a letter or

underscore. Identifiers can be as long as you

like, but most compilers will only recognize

the first few hundred characters. The compiler

distinguishes between upper- and lowercase

letters, so Var is not the same as var or VAR.


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keyword You cant use a C++ keyword as a variable

name. A keywordis a predefined word with aspecial meaning. int, class, if, andwhile are

examples of keywords. A complete list of

keywords can be found in Appendix B.

A variables name should make clear to anyone

reading the listing variables purpose and howit is used. Thus a variable int age is better

than something simple like int a or int aa.

The statements var1 = 20; var2 = var1 + 10;assign values to the two variables.

The equal sign (=), causes the value on the

right to be assigned to the variable on the

left. in the statement var1 = 20; var1, which

had no value, is given the value 20.


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Integer constant The number 20 is an integer constant.Constants

dont change during the course of the program. An integer constant consists of numerical

digits. There must be no decimal point in an

integer constant, and it must lie within the

range of integers.

In the second program line, the plus sign (+)adds the value of var1 and 10, in which 10 is

another constant. The result of this addition

is then assigned to var2.

The statement cout


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cout


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The endl Manipulator The last cout statement in the INTVARS program

ends with an unfamiliar word: endl. Thiscauses a linefeed to be inserted into the

stream, so that subsequent text is displayed

on the next line.

It has the same effect as sending the \n

character, but is somewhat clearer.

Its an example of amanipulator. Manipulators

are instructions to the output stream that

modify the output in various ways; well see

more of them as we go along. Strictly

speaking, endl (unlike \n) also causes the

output buffer to be flushed, but this happens

invisibly so for most purposes the two are

equivalent.


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C++ Data TypesData Type Size Range

bool 1 byte true(1) or false(0)

(signed)char 1 byte (-27)~(+27-1) = -128 ~ +127

unsigned char 1 byte 0 ~ 28-1 = 0 to 255 or

256 Different ASCII Characters

short(short int)

2 bytes (-215)~(+215-1) =-32,768 ~ +32,767

unsigned short 2 bytes 0 ~ 216-1 = 0 to 65,536

int

(signed int)

4 bytes (-231)~(+231-1) =

-2147483648 ~ +2147483647unsigned int 4 bytes 0 ~ (232-1) =

0 ~ 4,29,49,67,296

long

(long int)

4 bytes (-231)~(+231-1) =

-2147483648 ~ +2147483647


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C++ Data TypesData Type Size Range

unsigned

long

4 bytes 0 ~ 4,29,49,67,296

float 4 bytes (1.2 10-38 ~ 3.4 1038)

double 8 byte +(2.2 10-308 ~ 1.7 10308)

-(2.3 10-308 ~ 1.7 10308)

specifying type long will guarantee a four-bit

integer type on a 16-bit system such as MS-DOS

In 16-bit systems, type int has the same range

as type short.

On all systems type short occupies two bytes.


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C++ Data Typeslong v1 = 7678L; // assigns long constant

// 7678 to v1 of type long

Many compilers offer integer types that

explicitly specify the number of bits used.

They are __int8, __int16, __int32, and __int64

char data type is used to store numbers thatconfine themselves to a limited range, but it

is commonly used to storeASCII characters.

ASCII character set is a way of representing

English alphabet in a 8-bit space.

Character constants use single quotation marksaround a character, like a and b. (Note

that this differs from string constants, which

use double quotation marks)


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C++ Data Types When the C++

compilerencounters such a

character

constant, it

translates it into

the correspondingASCII code.

The constant a

appearing in a

program, for

example, will betranslated into

97, as shown in

Figure.


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Programming Example// charvars.cpp

// demonstrates character variables

#include //for cout, etc.


intmain()

{

char charvar1 = 'A'; //define character variable

char charvar2 = '\t'; //define character variable

cout


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Escape sequence '\t' and '\n', are special character with have

different behavior. These are called escapesequence. The name reflects the fact that the

backslash causes an escape from the normal

way characters are interpreted.

In this case the t is interpreted not as the

character 't' but as the tab character. A tabcauses printing to continue at the next tab

stop.

cout


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Escape sequenceThis translates to

"Run, Forrest, run," she said.

Sometimes you need to represent a character

constant that doesnt appear on the keyboard,

such as the graphics characters above ASCII

code 127.

To do this, you can use the '\xdd' representa-

tion, where each dstands for a hexadecimal

digit. If you want to print a solid rectangle,

for example, youll find such a character

listed as decimal number 178, which ishexadecimal number B2 in the ASCII table.

cout


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ASCII TABLE

#include

#include


intmain(){

unsigned char ch;

for(ch=0 ; ch


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Input with cin#include //for cout, etc.

#include


intmain(){

int A,B,AVG; // run again for float data type

cout >A;

cout B;

cout


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Input with cin// fahren.cpp

// demonstrates cin, newline

#include


intmain()

{

int ftemp; //for temperature in fahrenheit

cout ftemp;

int ctemp = (ftemp-32) * 5 / 9;

cout


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Input with cin The statement cin >> ftemp; causes the program to wait

for the user to type in a number. The resulting number is placed in the variable ftemp. The

keyword cin (pronounced C in) is an object, predefinedin C++ to correspond to the standard input stream.

This stream represents data coming from the keyboard(unless it has been redirected).

echo 100 | first.exe (type in DOS)

The >>is the extraction or get from operator. It takes

the value from the stream object on its left and places

it in the variable on its right.


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Input with cin insertion operator >can be used repeatedly with

cin, allowing user to enter a series of values.

Any arrangement of variables, constants, andoperators that specifies a computation is called an

expression, Thus, alpha+12 and (alpha-37)*beta/2are expressions.

Statements tell the compiler to do something and

terminate with a semicolon, while expressionsspecify a computation.

T

here can be several expressions in a statement. If both *(multiply) and -(subtract) are present in

an expression then the multiplication would be

carried out first, since * has higher priority Than

* and / have the same precedence. the one on theleft is executed first


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Floating Point Types They have both an integer part, to the left

of the decimal point, and a fractionalpart, to the right.

Floating-point variables represent what

mathematicians call real numbers, which are

used for measurable quantities such asdistance, area, and temperature. They

typically have a fractional part.

There are two kinds of floating-point

variables in C++: float, double.

float data type occupies 4 bytes (32bits)

in memory while double occupies 8 bytes of

memory.


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Float Example

// circarea.cpp

// demonstrates floating point variables



intmain()

{float rad; //variable of type float

const float PI = 3.14159F; // type const float

cout > rad; // get radius

float area = PI * rad * rad; // find area

cout


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Code Explanation The number 3.14159F is an example of a

floating-point constant. The decimal point signals that it is a

floating-point constant, and not an integer.

The F specifies that its type float, rather

than double or long double.

The number is written in normal decimal

notation.

With type long double, use the letter L.

You can also write floating-point constants

using exponential notation e.g. 1234.56 wouldbe written 1.23456E3.

The keyword const (for constant) specifies

that the value of a variable will not change

throughout the program.


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Quadratic Equation: Y = X2-6X-7


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Float Example: Quadratic Equation

// A program to calculate Y = X2-6X-7



intmain(){

float X,Y; //variable of type float

cout X; // get value of x

Y = (X*X)-(6*X)-7; // find y

// display answer

cout


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Calculating Roots ofQuadratic Equation// Calculating Roots

#include #include

#include


intmain(){

double a,b,c,x1,x2; // variable of type float

cout b >> c; // get first a then b & c

cout


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Assignment #1

1. What is the correct variable type for storing the

following data: The number of pages in your text book

The cost of this book

The age of a person

The number of people in the world

2. Write a program that calculates and prints sum,difference and product of two numbers. Also, usethis program to calculate remainder and quotient indivision of these numbers. Display the output onthe screen.

3. Write a program that gets 6 integers from the userand displays the sum, average and product ofthese numbers on screen.


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The setw() Manipulator#include

#include using namespace std;

intmain(){

longpop1=2425785, pop2=47, pop3=9761;

cout


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The setw() Manipulator#include

#include // for setw#include


intmain(){

longpop1=2425785, pop2=47, pop3=9761;

cout


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The setw() Manipulator The setw manipulator causes the number (or string)

that follows it in the stream to be printed withina field n characters wide, where n is the argument

to setw(n).

The value is right justified within the field.


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The Data Types Range#include


intmain(){

signed char ch = 127;

cout


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The Data Types Range// signtest.cpp tests signed and unsigned integers


intmain(){

int signedVar = 1500000000; //signed

unsigned int unsignVar = 1500000000; //unsigned

signedVar = (signedVar * 2)/3; //calculation exceeds range

unsignVar = (unsignVar * 2)/3; //calculation within range

cout


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Type Conversion// shows mixed expressions


intmain(){

int count = 7;

float avgWeight = 155.5F;

double totalWeight = count * avgWeight;

/* the lower-type variable is converted to the type of the

higher-type variable. Thus the int value of count is

converted to type float and stored in a temporaryvariable before being multiplied by the float variableavgWeight. The result (still of type float) is thenconverted to double so that it can be assigned to the

double variable totalWeight *********/cout


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Type Conversion


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Type Cast In C++ the term applies to data conversions

specified by the programmer, as opposed to theautomatic data conversions.

Sometimes a programmer needs to convert a value

from one type to another in a situation where thecompiler will not do it automatically or without

complaining.

Heres a statement that uses a C++ cast to change a

variable of type int into a variable of type char:

aCharVar = static_cast(anIntVar);

Here the variable to be cast (anIntVar) is placed

in parentheses and the type its to be changed to(char) is placed in angle brackets.


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Type Conversion// cast.cpp

// tests signed and unsigned integers#include


intmain()

{

int intVar = 1500000000; //1,500,000,000

intVar = (intVar * 10) / 10; //result too largecout


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The Remainder Operator (%)// remaind.cpp demonstrates remainder operator


intmain(){

cout


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Arithmetic Assignment Operators, += , -= , *= , /= , %=

// demonstrates arithmetic assignment operators


intmain(){

int ans = 27;

ans += 10; //same as: ans = ans + 10;

cout


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Increment Operators, ++ , --

// increm.cpp demonstrates the increment operator

#include


intmain(){

int count = 10;

cout


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Linker and Compiler


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Assignment #2

Answer all questions from Q1 to Q25 andExercise 1 to 12 of Chapter2.

Documents

Ch02 C++ Programming Basics