Practical basics on c++

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Practical basics on writing C++
Basic operations quick guide

I/O and math operation symbols
libraries to include
heading and functions
1
#include <iostream> //proprocessor direcrive
using namespace std;
code for output
cout << "Hello word!n; //this istruction can be write as
//cout << "Hello word!" << endl;

libraries to include
heading and functions
2
#include <iostream> //proprocessor direcrive
code for input
int number; //name of variable
cin >> number; //reading by system of variable

sum of two operators
+
- subtraction of two operators
division of two operators
/
* product of two operators
calculation of the change in a division between two operators
%

retention of a number in an element
=
== comparision of two elements
increment of 1
++
-- decrease of 1

member b of object a
a.b
*x pointed to by x
adress of x
&x
x->y member y of object pointed to by x
object pointed to by x
x[n]

Mix input data with output messages
code from text editor
#include <iostream>
int main () {
cout << “Enter a number.n”;
int number;
cin >> number;
cout << “You have endered the number “ << number << endl; //”number”;
return 0; //this istruction return the command to OS and exits from the program
}
result from terminal
Enter a number.
4
You have entered the number 4.

Condition if…else
#include <iostream>
int main () {
cout << “Enter a number.n”;
int number;
cin >> number;
if (number < 10) { //condition
cout << “The number entered is less than 10.n”; reutrn 0; }
else
cout << “The number entered is higher than 10.n”; return 0;
}
Enter a number.
7
The number entered is less than 10.
Enter a number.
25
The number entered is higher than 10.
This function can be used to
manage errors by user.

Condition switch
#include <iostream>
int main () {
cout << “Enter 1 to print a message, press 2 to exitn”;
int number_selection;
cin >> number_selection;
switch (number_selection) {
case 1:
cout << “Hi!n”;
return main ();
case 2:
return 0;
default:
cout << “Error! Please, press 1 or 2 keypass.n”;
return main ();
}
}
project a menu, for example.
1

Condition switch
Enter 1 to print a message, press 2 to exit.
1
Hi!
2
project a menu, for example.
3
Error! Please, press 1 or 2 keypass.
2

Cycles: for
#include <iostream>
int main () {
for (int a = 10; a < 20; a = a+1)
{
cout << “Value: " << a << “.n”;
}
return 0;
}
Value: 10.
Value: 11.
Value: 12.
Value: 13.
Value: 14.
Value: 15.
Value: 16.
Value: 17.
Value: 18.
Value: 19.
Be careful to loops!

Cycles: while
#include <iostream>
int main () {
int n = 10; //initialisation
while (n>0) { cout << n << ", ";
--n;
}
cout << "liftoff!n";
}
10, 9, 8, 7, 6, 5, 4, 3, 2, 1, liftoff!

Cycles: do…while
//example of an echo machine
#include <iostream>
#include <string>
int main () {
string str;
do {
cout << "Enter text. ";
getline (cin,str);
cout << "You entered the following sentence.n " << str << 'n';
}
while (str != "goodbye");
}
Enter text.
Hello!
You entered the following sentences.
Hello!
do…while executes at least once
the operation, while while and
for could not execute that.

Arrays and vectors: creations and operations
//declaration of array
int name_of_array[10]; //the array’s size is 10
for(int i=0; i < 14; i++) //initialisarion of array
{
cout << name_of_array[10] << endl; //array’s printing
}
1

another example
#include <iostream>
int foo[] = {16, 2, 77, 40, 12071};
int n, result=0;
int main () {
for ( n=0; n<5; ++n) {
result += foo[n];
}
cout << result; return 0;
}
12206
2

Classes
public class
#include <iostream>
class rectangle {
int width, height;
public:
rectangle ();
rectangle (int,int);
int area (void) {
return (width * height);
}
};
rectangle::rectangle ()
{width = 5; height = 5;
}
rectangle::rectangle (int a, int b)
{width = a;
height = b;
}
int main () {r
rectangle rect(3,4);
rectangle rectb;
cout << “rect area: " << rect.area() << endl;
cout << "rectb area: " << rectb.area() << endl;
return 0;
}
By default, in C++ the programmer
insert private class type.
1

Classes
output from bash
rect area: 12
rectb area: 25
2

Compiling operation
command from bash
g++ <name_of_source_code>.cpp –o <name_of_executable>

Run command
command from bash
./<name_of_executable>

Index
I/O and math operations symbols
Mix input data with output messages
Condition if…else
Compiling operation
Classes
Cycles: for
Cycles: while
Cycles: do…while

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Practical basics on c++

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