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(1.1) INTRODUCTION
Generally a program executes its statements from beginning to
the end, but all programs don't follow this. This presentation will
tell us in detail about the program control statements.

(1.2) STATEMENTS
Statements are the instructions given to the computer to perform
any kind of data movements, be it making decisions or repeating
actions. They form the smallest executable unit of the program.
They are terminated by a semicolon(;). The different types of
statements are:-

(1.2.1) Compound statements(Block)
A block is a group of statements that are enclosed in a pair of
curly brackets:-
{
statement:-1
statement:-2
}
It may appear anywhere in a program as a single statement of the
program. A block is many times known as compound statements.

(1.3)STATEMENT FLOW CONTROL
In a program, statements may be executed sequentially , selectively
or iteratively:-

Sequence:- This is the default flow of the statements and also
known as sequence construct and it also means that
the statements are being executed sequentially.
Selection:- The selection construct means that the execution of
the statements depends on a condition-test, if the
condition is true then the statements would be
executed else they would be skipped. An else-if
statement is a good example of selection statement.

Iteration:- The iteration means repetition of a certain set of
statements based on a certain condition-test.
Looping statements can be used to perform the
repetition of a certain set of statements.
They are of three types:- for loop, Do-while loop
(1.4) SELECTION STATEMENTS
and while loop.
They allow to choose a certain set of statements for execution only if
a condition is true. There are two types of selection statements
provided by c++ namely if statement and switch statement.

(1.4.1) THE IF STATEMENT OF C++
An if statement tests for a particular condition, if the statement is
true then the particular set of statements is executed else they are
skipped.

The syntax for the if statement is :-
If(condition)
statement;
The statement can either be a single statement or a block. We can
also use nested if statements or a ladder of if statements if required
in our program.

(1.4.2)THE SWITCH STATEMENT
C++ provides another type of selection statement i.e. switch statement.
The selection statement successively tests the value of an expression
against a list of integer or character constants. When a match is found,
the statements associated with that constant are executed.

The syntax for a switch statement is :-
Switch(expression)
{
case constant 1: statement sequence 1
break;
break;
break;
case constant n-1: statement sequence n-1;
break;
default : statement sequence n;
}

(1.5) ITERATION STATEMENTS
Iteration statements in c++ allows a certain number instructions to
be performed repeatedly until a certain condition becomes false.
Iteration statements are also called loops or looping statements.
C++ allows the use of three loops namely:-for loop, while loop, do-
while loop.

(1.5.1) ELEMNTS THAT CONTROL A LOOP
Every loop has its elements that control and govern the execution.
Generally, a loop has 4 elements that have different purposes. These
elements are as given below:-

1. Initialization Expression(s):
Before entering the loop the initialization expression(s) initializes
the loop control variables with their first values.
2. Test Expression:
The test expression is that expression whose truth value decides
whether the loop-body will be executed or not. If the value is true
then the body gets executed else it gets terminated.

3. Update expression(s): The update expression(s) change the
value(s) of loop variable(s). The update expression execute at the
end of the loop.
4. The Body-of-the-loop: The statements that are to be
executed form the body-of-the-loop.
(1.5.2) THE FOR LOOP
The for loop is the easiest to understand of all because all its loop-
control elements are gathered in one place i.e. at the top. Its syntax
is:-
For(initialization expression(s);test—expression; update expression)
body-of-the-loop;
The following slide explains the working of the for loop with an e.g:

#include<iostream.h>
int main()
{
int i;
for(i=1;i<=10;i++)
cout<<“n”<<i;
return 0;
}
 Firstly, initialization expression is executed i.e., i=1 which
gives the first value 1 to variable i.
 Then, the test-expression is executed i.e., i<=10 which results
into true i.e., 1.
 Since, the test expression is true, the body-of-the-loop i.e.,
cout<<“n”<<i is executed which prints the current value of i
on the next line.

 After executing the loop-body, the update expression i.e., i++
is executed which increments the value of i.
 After the update expression is executed, the test-expression is
again evaluated. If it is true the sequence is repeated from
step no. 3, otherwise the loop terminates.

(1.5.3) THE WHILE LOOP
The second loop provided by c++ is the while loop. It is an entry
controlled loop. The syntax for a while loop is:-
while (expression)
loop-body
Where the loop may contain a single statement, a compound
statement or an empty statement. The loop iterates while the
expression is true. When the expression becomes false, the program
control terminates the loop.

In a while loop, a variable should be initialized before the loop as
uninitialized variables cannot be used in the loop. The loop variable
should be updated inside the body-of-the-loop. Following example
explains the working of a while loop:-
int i,fact=1,n;
cout<<“Enter a number.”;
cin>>n;
i=1;
while(i<=n)
{
fact=fact×I;
i=i++;
}
cout<<“The factorial of the num.=“<<fact;

The program segment in the previous slide would input a number
from the user and print the factorial of the number.

(1.5.4) THE DO-WHILE LOOP
Unlike the for and while loop do-while loop is an exit controlled loop
i.e., it evaluates the test-expression at the bottom of the loop after
the body-of-the-loop. This means that the do-while loop always
executes at least once. The syntax for do-while loop is:-
do
{
statement;
}
while(test-expression)
The brackets { } are not necessary when there is only one statement in
the loop-body.

An example for do-while loop is:-
int i=1,n=10002;
do
{
cout<<n;
n++;
i++;
}
while(i==1);
In the above example the test expression is never true but still
every time the loop is executed the loop would execute only once
and print “10002”.

(1.5.5) NESTED LOOPS

C++ allows its users to use a number of loops inside a single loop,
hence it means that c++ allows the use of nested loops. A user can
use nested loops according to his own requirement. The following
example explains the use of nested loops:-
for(i=1;i<=4;i++)
{
cout<<“n”;
for(j=1;j<=i;j++)
cout<<“*”;
}
In the above program the inner loop will execute for i number of
times and i has values 1,2,3,4.

The output of the above program segment would be:-
*
**
***
****

(1.6) JUMP STATEMENTS
Jump statements unconditionally transfer program control within
a function. C++ has four jump statements that perform an
unconditional branch: return, goto, break, and continue. Of these
return and goto maybe used anywhere in the program but break
and continue can be used only inside brackets { } .

(1.6.1) THE GOTO STATEMENT
A goto statement can statement can transfer the program control
anywhere in the program. The target destination of a goto
statement is marked by a label. The target label and goto must
appear in the same function.

(1.6.2) THE BREAK STATEMENT
The break statement enables the user to skip over a part of the
program. The break statement is used inside brackets { }. It brings
the program control directly outside the brackets { }.
(1.6.3) THE CONTINUE STATEMENT
The continue statement skips a certain part of the code but does
not terminate the loop but skips a certain part of the code.

(1.6.4) THE EXIT() FUNCTION
The library function exit() takes u directly outside the program. It
does not even stop for the getch() function. It terminates the
program as soon as it is encountered no matter where it appears.

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