#include <iostream>
using namespace std;
int main()
{
for (int -21; i <31; i++)
cout << "value of i:"<<<i<<< endl;
return 0;
}
Output
Value of i: 21
Value of i: 22
Value of i: 23
Value of i: 24
Value of i: 25
Value of i: 26
Value of i: 27
Value of i: 28
Value of i: 29
Value of i: 30

Output:
2 4 6 8 10.

Null statement
The "null or empty statement" is a statement containing only a semi colon. It takes the following
form:
;// it is a null statement.
Null statement are commonly used as place holders in iteration statements or as statements on which to place labels at the end of compound statements or functions.
Compound statement
C++ allows a group of statements enclosed by pair of braces (). This group of statements is called as a compound statement or a block.
The general format of compound statement is:
{
statement 1;
statement 2;
statement 3;
}
for example:
{
int a,b;
a-8;
b=a+8;
}

A	B
(a) Modulus	(2) Remainder of a division
(b) Separators	(3) Punctuators
(c) Stream extraction	(4) get from
(d) Lexical Units	(1) Tokens

(i) 39 - Decimal
(ii) 032 - Octal
(iii) 0XCAFE - Hexadecimal
(iv) 04.14 - Decimal

Keywords are the reserved words which convey specific meaning to the C++ compiler. They are the essential elements to construct C++ programs. Most of the keywords are common to C, C++ and Java. Keywords are reserved and cannot be used as identifiers.

C++ program statements are constructed by many different small elelments such as commands, variables, constants and many more symbols called as operators and punctuators. Individual elements are collectively called as Lexical units or Lexical elements or Tokens. C++ has the following tokens:
(i) Keywords
(ii) Identifiers
(iii) Literals
(iv) Operators
(v) Punctuators

#include <iostream>
using namespace std;
int main()
{
cout<<"\n PRINT SERIES";
for (int i=1;i< 40; i=i+3)
cout << i << "1+";
cin.get():
return ();
}

The switch statement is a multi-way branch statement. It provides an easy way to dispatch execution to different parts of code based on the value of the expression. The switch statement replaces multiple if-else sequence.
The syntax of the switch statement is;
switch(expression)
{
case constant 1:
statement(s);
break;
case constant 2:
statement(s);
break;
.
.
.
.
default:
statement(s);
}

The syntax of if-else ladder:
#include <iostream>
using namespace std;
int main()
(
int num:
cout<<"Enter Number to find its multiplication table";
cin >> num;
for (int a = 1; a<= 10; a++)
{
cout << num << "*" << a << "=" << num*a << endl;
}
return 0;
}

C++ program is a collection of functions. Every C++ program must have a main function. The main() function is the starting point where all C++ programs begin their execution. Therefore, the executable statements should be inside the main() function.

=	==
" = "is an assignment operator	" == " is an equal to operator and it is a relational operator.
It is used to assign the value of variable or expression	It is used for comparison of both left and right side operands.
Eg: a = b (b value is assigned to a)	Eg: a==b (a value will be compared with b value).

C++ is a case sensitive programming language so, all the keywords must be in lowercase. Case sensitive means that the uppercase and lowercase letters are considered differently.

Keywords	Identifiers
Keywords are the reserved words which convey specific meaning to the C++ compiler.	Identifiers are the user-defined names given to different parts of the the C++ program.
They are the essential elements to construct C++ programs.	They are the fundamental building blocks of a program.
Most of the keywords are common to C, C++ and Java.	Every language has specific rules for naming the identifiers.

An entry control loop checks the condition at the time of entry and if condition or expression becomes true then control transfers into the body of the loop. for loop and while loop are the examples of Entry Controlled Loop.
A while loop is a control flow statement that allows the loop statements to be executed as long as the condition is true.
Type: Entry control loop
Syntax:
while ( Text expression)
{
Body of the loop;
}
Statement-x;
The control flow and flow chart of the while loop is shown below:

Control flow:
Step 1: Test-expression is evaluated to either True or False;
Step 2: If test-expression is true;
(a) The body of the loop is executed.
(b) Control is transferred to step 1.
Step 3: If test-expression is false, the control exits the while loop.
Example:
int a = 1;
while (a<-10)
{
cout< a+=2;
}
Output
1 3 5 7 9

Type of Error	Description
Syntax Error	Syntax errors occur when grammatical rules of C++ are violated.
Semantic Error	Semantic Error occur when there is wrong use of variable/ operator/order of execution etc. It is also called as Logical Error.
Run-time error	A run time error occurs during the execution of a program. It is occurs because of some illegal operation that takes place.