Looping statement
It is also called a Repetitive control
structure. Sometimes we require a set of statements to be executed a number of
times by changing the value of one or more variables each time to obtain a
different result. This type of program execution is called looping. C++
provides the following construct
·
while
loop
·
do-while
loop
·
for
loop
While
loop
Syntax of while loop
while(condition)
{
statement(s);
}
{
statement(s);
}
The flow diagram indicates that a condition is
first evaluated. If the condition is true, the loop body is executed and the
condition is re-evaluated. Hence, the loop body is executed repeatedly as long
as the condition remains true. As soon as the condition becomes false, it comes
out of the loop and goes to the statement next to the ‘while’ loop.
do-while
loop
Syntax of do-while loop
do
{
statements;
} while (condition);
{
statements;
} while (condition);
Note :
That the loop body is always executed at
least once. One important difference between the while loop and the do-while
loop the relative ordering of the conditional test and loop body execution. In
the while loop, the loop repetition test is performed before each execution the
loop body; the loop body is not executed at all if the initial test fail. In
the do-while loop, the loop termination test is Performed after each execution
of the loop body. hence, the loop body is always executed least once.
for
loop
It is a count controlled loop in the sense that
the program knows in advance how many times the loop is to be executed.
syntax of for loop
for (initialization; decision; increment/decrement)
{
statement(s);
}
for (initialization; decision; increment/decrement)
{
statement(s);
}
The flow diagram indicates that in for loop three
operations take place:
·
Testing of
loop control variable
·
Update the
loop control variable either by incrementing or decrementing.
Operation (i) is used to initialize the value. On
the other hand, operation (ii) is used to test whether the condition is true or
false. If the condition is true, the program executes the body of the loop and
then the value of loop control variable is updated. Again it checks the
condition and so on. If the condition is false, it gets out of the loop.
Jump
Statements
The jump statements unconditionally transfer
program control within a function.
·
goto
statement
·
break
statement
·
continue
statement
The goto statement
goto allows to make jump to another point in the program.
goto pqr;
pqr: pqr is known as label. It is a user defined identifier. After the execution of goto statement, the control transfers to the line after label pqr.
goto allows to make jump to another point in the program.
goto pqr;
pqr: pqr is known as label. It is a user defined identifier. After the execution of goto statement, the control transfers to the line after label pqr.
The break statement
The break statement, when executed in a switch structure, provides an immediate
exit from the switch structure. Similarly, you can use the break statement in
any of the loop. When the break statement executes in a loop, it immediately exits from the loop.
The break statement, when executed in a switch structure, provides an immediate
exit from the switch structure. Similarly, you can use the break statement in
any of the loop. When the break statement executes in a loop, it immediately exits from the loop.
The continue statement
The continue statement is used in loops and causes a program to skip the rest of the body of the loop.
while (condition)
{
Statement 1;
If (condition)
continue;
statement;
}
The continue statement skips rest of the loop body and starts a new iteration.
The continue statement is used in loops and causes a program to skip the rest of the body of the loop.
while (condition)
{
Statement 1;
If (condition)
continue;
statement;
}
The continue statement skips rest of the loop body and starts a new iteration.
The exit ( ) function
The execution of a program can be stopped at any point with exit ( ) and a status code can be informed to the calling program. The general format is
exit (code) ;
where code is an integer value. The code has a value 0 for correct execution. The value of the code varies depending upon the operating system.
The execution of a program can be stopped at any point with exit ( ) and a status code can be informed to the calling program. The general format is
exit (code) ;
where code is an integer value. The code has a value 0 for correct execution. The value of the code varies depending upon the operating system.
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