C++ Programming

A file mode describes how a file is to be used, to read, to write to append etc. When you associate a stream with a file, either by initializing a file stream object with a file name or by using open() method, you can provide a second argument specifying the file mode.

e.g. stream_object.open("filename",filemode);

Following is the list of filemodes available in C++

ios::in

ios::out

ios::binary

ios::ate

ios::app

ios::trunc

ios::nocreate

ios::noreplace

I've written a Blog about the same topic in relation to some events in my country: http://srijanfoundation.wordpress.com/2007/11/02/chak-de-india-the-non-message/.

Love,

Rahul Dewan

--

http://srijanfoundation.wordpress.com/

http://srijantech.wordpress.com/

http://www.srijan.in

void foo (char& c)

{

cin >> c;

}

int main()

{

char ch[10] {};

for (size_t c=0; c!=10; ++c)

foo (c[0]);

}

Destructors are used to free memory and release resources.

The getchar() function is used to read a single character from standard input (stdin) and increment the associated file pointer to point to the next character. The return value is an integer which must be cast to a character.

An example demonstrating its usage is shown below.

#include <stdio.h>

int main()

{

char buffer[81];

int i, ch;

for(i=0; (i<80) && ((ch = getchar()) != EOF) && (ch!='\n'); ++i)

{

buffer[i] = (char) ch; // cast input to a character

}

buffer[i] = '\0'; // add null-terminator.

printf( "You entered: %s\n", buffer);

}

Global Varible:

The variable which is declared as "Global" one : having the preveleges to use and access that variable in any class and object( means any where in the program) just like PUBLIC keyword in OOPS concepts.

Static Variable :

If we declare a variable as Static , then it wont have the permission to access that variable through out the program and u have to use it inside the class or object which u declared itself.

All the Best

Annapurna

Hmm...
Visual C++ isn't really a language, it's more like an environment in which you can create programs using different tools.
Anyway, C++ is the best language you can learn if you want to get started as a game programmer. It's the most efficient and it's probably gonna stay that way. Hope that helped.


Rocamora

Modularisation. It could also be called refactoring, where large and complex functions are split into several simpler functions, making code easier to read. Refactoring can also help to reduce code duplication.

A default constructor is one that has no parameters (C++ also calls constructors with all default parameters a default constructor), while a parameterized constructor is one that has at least one parameter without a default value. Default constructors can be provided by the compiler if no other constructors are defined for that class or any class the class inherits from, while parameterized constructors must always be defined by the developer.

There is no such thing as a constructor function in C++ (constructors have no return value, not even void, and cannot be called like regular functions). Constructors are invoked rather than called directly, either by declaring a static variable of the class type, or via the C++ new operator.

Subscripts are used to identify the elements in an array, where the first element has subscript 0. Thus an array of n elements has subscripts in the range 0 to n-1. Each element may itself be an array, thus allowing multi-dimensional arrays.

The subscript may be a constant or a variable. However, when declaring a static array, the subscript must be a constant. Constants include literal constants as well as named constants.

A subscripted variable is simply an array or a datatype that can be divided into an array. For instance, a 32-bit int can be treated just as if it were an array of two 16-bit shorts or four 1-byte chars.

Thus in the 32-bit int array, int i[10], i is a subscripted variable where i[0] is the first integer and i[9] is the last. If we then say char*c=&i, c would allow us to treat i as if it were a subscripted variable with 40 char elements (c[0] to c[39]).

Integers are always guaranteed to be precise, provided you have sufficient bits to represent the number (plus the sign, if required). All logical and mathematical operations are extremely efficient when working with integers, even with division which simply truncates any fraction. If that's all the precision you need then you don't need to use a float. But if you need real numbers, then you must use a float.

Floating point numbers are never guaranteed to be accurate. Irrational numbers (such as pi and 1/3) are impossible to represent fully within a finite number of bits, thus there has to be a degree of precision. All floating point numbers are actually represented in computer memory using the binary equivalent of scientific notation, so even when dealing with small integer values, logic errors can creep in (such as 0.9 + 0.1 == 1.000000...01). Thus when working with floats you have to accommodate for the degree of precision.

Due to the increased complexity of floating point numbers, they are much less efficient than when working solely with integers. Thus if you can guarantee that a floating point number can be accurately represented as an integer (no fractions), then it makes more sense to use an integer. However, if you cannot make that guarantee then you must use a float.

Integer division can be problematic due to truncation, so it's often necessary to cast integers to floats to obtain a higher degree of precision, rounding the result as appropriate before casting back to an integer. Repeatedly converting back and forth can be costly, so it's sometimes better to just work with a float from the outset.

#include <iostream>

bool isPrime(int p)

{ if( p<=1 ( p>2 && p%2==0 ))return( false );int max = (int)sqrt(( double ) p ) + 1;for( int i=3; i<=max; i+=2 )if( p%i==0 )return( false );return( true );

}

int main()

{ int primes[10];

int count=0, num=0;

while( count!= 10 )

{num+=num>2?2:1;if( isPrime(num) )primes[count++]=num;}for( int i=0; i<10; ++i )std::cout << primes[i] << std::endl;return( 0 );

}

You don't need any "subjects" (whatever that means). Simply read the documentation that came with the update.

When a function gets called, the processor first stores the address of the calling function in a structure called activisation structure and jumps to the called function. Then it allocates the memory for the local variables and initializes them. Then it does the processing in that function. After that it deallocates the memory allocated for the local variables and returns to the calling function. When a function gets called, the processor first stores the address of the calling function in a structure called activisation structure and jumps to the called function. Then it allocates the memory for the local variables and initializes them. Then it does the processing in that function. After that it deallocates the memory allocated for the local variables and returns to the calling function.

The following code will convert any number in any base to any other base, from binary to hexadecimal, and everything inbetween.

#include<iostream>

#include<string>

#include<sstream>

typedef unsigned long long ull;

typedef unsigned long ul;

const std::string symbols="0123456789abcdef";

std::string inputvalue(ul base)

{

using namespace std;

string value;

while(1)

{

cout<<"Enter a positive value : ";

string s;

getline(cin,s);

if(s.size())

{

for(string::iterator i=s.begin();i!=s.end();++i)

if(*i>='A' && *i<='Z')

*i+=32;

string actual = symbols.substr(0,base);

if(s.find_first_not_of(actual)!=string::npos)

{

cout<<"The value you entered is invalid for the base.\n"

<<"Please enter another value.\n"<<endl;

continue;

}

value=s;

break;

}

}

return(value);

}

ul inputbase(std::string prompt)

{

using namespace std;

ul result=0, min=2, max=16;

while(1)

{

cout<<prompt.c_str()<<" ["<<min<<".."<<max<<"] : ";

string s;

getline(cin,s);

if(s.size())

result=stoul(s,0,10);

if(result<min result>max)

cout<<"The base must be in the range "

<<min<<".."<<max<<"\n"

<<"Please enter another base.\n"<<endl;

else

break;

}

return(result);

}

ull base2dec(std::string value,ul base)

{

ull col=1, num=0;

for(std::string::reverse_iterator i=value.rbegin(); i!=value.rend(); ++i)

{

num+=symbols.find(*i,0)*col;

col*=base;

}

return(num);

}

std::string dec2base(ull dec,ul base)

{

using namespace std;

int len=1;

ull tmp=dec;

while(tmp/=base)

++len;

string value("0",len);

while(dec)

{

value[--len]=symbols[dec%base];

dec/=base;

}

return(value);

}

int main()

{

using namespace std;

ul base=inputbase("Enter the base of the value");

string value=inputvalue(base);

ul newbase=inputbase("Enter the base to convert to");

value=dec2base(base2dec(value,base),newbase);

cout<<"New value:\t"<<value.c_str()<<endl;

return(0);

}

By "other forms" I presume you mean forms outside of your application. The only way to modify their properties is via the interface provided by those forms. You also need to be aware that those forms can fall from scope at any time.

biome climate zone

Am not sure it is a good idea to embed the integer as a string. Aside from the inefficiency of storing a 5-digit number as a string, what would be the expected result of adding two IntStr objects together? E.g., "40" + "2" could either be "42" (add), or "402" (append) depending on your intentions. And if you wished to add an IntStr and an integer, such as "40" + 2, then you'd have to convert the embedded string back to an int, perform the addition, and if the sum is less than 100000, then convert the sum back to a string. This is highly inefficient. Personally, I'd embed the integer itself and provide accessors and casts to explicitly convert it to a string on an as-required basis only, since the numeric form is likely to be far more useful to you than the string form.

However, to answer the question as it stands, the following is one possible solution.

#include<iostream>

#include<string>

#include<sstream>

class IntStr

{

private:

std::string m_string;

public:

IntStr():m_string("0") {}

IntStr(const unsigned int decimal):m_string("0")

{

set_int(decimal);

}

IntStr& operator=( const unsigned int decimal )

{

return( set_int( decimal ));

}

std::string get_int()const{ return(m_string); }

IntStr& set_int(const unsigned int decimal)

{

if( decimal<100000 )

{

std::stringstream ss;

ss<<decimal;

m_string = ss.str();

}

return( *this );

}

};

int main()

{

IntStr a; // default constructor.

a = 42; // assignment operator.

IntStr b = a; // copy constructor.

IntStr c(1000); // user-defined constructor.

IntStr d(100000); // overflow check.

std::cout<<"a = "<<a.get_int().c_str()<<std::endl;

std::cout<<"b = "<<b.get_int().c_str()<<std::endl;

std::cout<<"c = "<<c.get_int().c_str()<<std::endl;

std::cout<<"d = "<<d.get_int().c_str()<<std::endl;

}

Example output:

a = 42

b = 42

c = 1000

d = 0

To include mysql.h you must first locate the mysql header file and its associated libmysql library file and DLL. If you don't have them, you must download them from the MySQL website, on the Downlads (GA) page (GA = generally available). Download and save the Windows version which includes everything (around 208MB). Once downloaded, proceed with the installation of MySQL. Choose the Developer Default, Full installation, or customise what you need.

To include mysql.h, you must specify the path to the file in Project Properties (ALT+F7) in the VC++ Directories > Include Directories. By default, this file resides in "<program files>\MySQL\Connector C 6.0.2\include". Do this for all configuration types (debug, release, etc) and for all projects that require MySQL.

Thereafter you can include mysql.h in any file that requires it:

#include <mysql.h>

You must also link with the appropriate library files. They can be found in "<program files>\MySQL\Connector C 6.0.2\lib", with separate folders for the debug and optimised (release) versions of each. Specify the appropriate folder in your Project Properties > VC++ Directories > Library Directories for each build type.

Finally, specify the required libraries in the Project Properties > Linker > Input > Additional Dependencies.

Note that prior to VS2010, include and library directories are assigned globally rather than per project, per build type. For earlier versions, look in Tools > Options > Projects and Solutions > VC++ Directories instead. For the library, you must include the lib folder only (not the debug or opt folders). And in the Project Properties, you must include the appropriate debug or opt path in your linker's Additional Dependencies (e.g., debug\libmysql.lib for debug builds and opt\libmysql.lib for release builds).

The following program shows one way to convert to BCD using a variation of packed BCD 8421 encoding. Each digit is represented by 4 bits in the range 0x0 to 0x9. 0xa denotes a minus symbol (for negative values) while 0xb denotes a decimal point for floating point values. The unused value 0xf is used to pad a BCD to a full byte when the number of symbols is odd. Values 0xc, 0xd and 0xe are ignored, but could be used for other purposes such as when representing exponents or fractions/ratios.

Values may be any length, the BCD being represented by a vector of type unsigned char. Since the value of a BCD could easily exceed the range of a long double or a 64-bit integer, conversion to these types is disabled. BCD values are constructed from an input string and converted back to a string for output.

Arithmetic operations can be overloaded to handle a BCD (using decimal notation arithmetic), however this has been left as an exercise for the reader.

#include<iostream>

#include<sstream>

#include<vector>

#include<exception>

using uchar = unsigned char;

class BCD_8421

{

private:

std::vector<uchar> v;

static const uchar lo_mask {0x0f};

static const uchar hi_mask {0xf0};

public:

BCD_8421 (void);

BCD_8421 (const BCD_8421&);

BCD_8421 (BCD_8421&&);

BCD_8421 (const std::string&);

BCD_8421& operator= (const BCD_8421&);

BCD_8421& operator= (BCD_8421&&);

BCD_8421& operator= (const std::string&);

static bool is_valid (const std::string& s);

operator std::string (void) const;

friend std::ostream& operator<< (std::ostream&, const BCD_8421&);

};

BCD_8421::BCD_8421 (void): v(1, 0) {}

BCD_8421::BCD_8421 (const BCD_8421& bcd): v (bcd.v) {}

BCD_8421::BCD_8421 (BCD_8421&& bcd): v (std::move(bcd.v)) {}

BCD_8421::BCD_8421 (const std::string& s): v{} { *this = s; }

BCD_8421& BCD_8421::operator= (const BCD_8421& bcd) { v=bcd.v; return *this; }

BCD_8421& BCD_8421::operator= (BCD_8421&& bcd) { v=std::move(bcd.v); return *this; }

BCD_8421& BCD_8421::operator= (const std::string& s)

{

v.clear();

uchar c {};

bool msb {false};

bool minus {false};

bool point {false};

bool error {false};

bool digit {false};

for (auto i=s.begin(); i!=s.end(); ++i)

{

if (!msb)

c = hi_mask;

uchar x;

switch (*i)

{

case ('0'):

if (!digit)

continue;

case ('1'):

case ('2'):

case ('3'):

case ('4'):

case ('5'):

case ('6'):

case ('7'):

case ('8'):

case ('9'):

digit = true;

x = *i - '0';

break;

case ('.'):

if (!point)

{

point = !point;

x = 10;

break;

}

else

error = !error;

case ('-'):

if (!minus && i==s.begin())

{

minus = !minus;

x = 11;

break;

}

default:

error = !error;

}

if (error)

{

v.clear();

v.push_back (hi_mask);

std::stringstream ss;

ss << "Error: invalid argument in BCD_8421.operator= ("" << s << "")";

throw std::invalid_argument (ss.str());

}

if (msb)

v.push_back ((c & lo_mask) | (x << 4));

else

c |= x;

msb = !msb;

}

if (msb && c)

v.push_back (c);

else if (!digit)

{

v.clear();

v.push_back (hi_mask);

}

return *this;

}

bool BCD_8421::is_valid (const std::string& s)

{

const std::string valid_chars {"0123456789-."};

if (s.find_first_not_of (valid_chars) != valid_chars.npos)

return false;

auto f = s.find ('-');

if (f != s.rfind('-') (f && f!=s.npos))

return false;

if (s.find ('.') != s.rfind('.'))

return false;

return true;

}

BCD_8421::operator std::string (void) const

{

std::stringstream ss;

bool digit {false};

bool point {false};

for (auto i : v)

{

bool msb {false};

do

{

uchar c {};

uchar x = msb ? i >> 4 : i & lo_mask;

switch (x)

{

case (0x0):

case (0x1):

case (0x2):

case (0x3):

case (0x4):

case (0x5):

case (0x6):

case (0x7):

case (0x8):

case (0x9): c = '0' + x; digit = true; break;

case (0xa): c = '.'; point = true; break;

case (0xb): c = '-'; break;

default: break;

}

if (point && !digit)

ss << '0';

if (c) ss << c;

msb = !msb;

} while (msb);

}

if (ss.str().back()=='.')

ss << '0';

return ss.str();

}

std::ostream& operator<< (std::ostream& os, const BCD_8421& bcd)

{

return os << static_cast<std::string> (bcd);

}

int main()

{

for (unsigned loop=0; loop<10; ++loop)

{

std::string input;

while (true)

{

std::cout << "Enter a numeric value: ";

std::cin >> input;

if (BCD_8421::is_valid (input))

break;

std::cerr << "Invalid input.\n";

}

try

{

BCD_8421 a = input;

std::cout << "You entered the value: " << a << std::endl;

}

catch (std::range_error& e)

{

std::cerr << e.what() << std::endl;

}

}

}