COMPUTER FUNDAMENTALS
LAB REPORT #09
Introduction to Loops
Objectives:
Familiarization with Loops in C++ Programming
1.
for Loop
2.
while Loop
3.
do while loop
4.
nested Loops
Loop:
Loops
in any programming language are simply the repetition of execution of sets of
statements. There are number of loop types that we can use to introduce
repetition
A
loop is a control structure that executes a block of code repeatedly until the
logical expression of the loop evaluates to false (or zero in C++).
A loop statement
allows us to execute a statement or group of statements multiple times and
following is the general from of a loop statement in most of the programming
languages:
Types of loops:
There
are three types of loops:
- while
- do
while
- for
- nested
for loop
A for
loop is a repetition control structure that allows you to efficiently write a
loop that needs to execute a specific number of times.
Syntax:
for
( init; condition; increment )
{
statement(s);
}
Example:
#include <iostream>
using namespace std;
int main ()
{
// for loop execution
for( int a = 10; a <
20; a = a + 1 )
{
cout << "value
of a: " << a << endl;
}
return 0;
}
While Loop:
A while loop statement repeatedly executes
a target statement as long as a given condition is true.
Syntax of while loop
while(condition)
{
statement(s);
}
Example:
#include <iostream>
using namespace std;
int main ()
{
// Local variable declaration:
int a = 10;
// while loop execution
while( a < 20 )
{
cout << "value of a: "
<< a << endl;
a++;
}
return 0;
}
Do while loop
Unlike
for and while loops, which test the loop condition at the top of
the loop, the do...while loop checks its condition at the bottom of the
loop.
A do...while loop is similar to a while
loop, except that a do...while loop is guaranteed to execute at least one time
Syntax:
The
syntax of a do...while loop in C++ is:
do
{
statement(s);
}while( condition );
Nested
Loops
A nested loop is a loop within a loop, an
inner loop within the body of an outer one. How this works is that the first
pass of the outer loop triggers the inner loop, which executes to completion.
Then the second pass of the outer loop triggers the inner loop again. This
repeats until the outer loop finishes. Of course, a break within either
the inner or outer loop would interrupt this process.
Example:
#include <iostream>
using namespace std;
int main ()
{
int i, j;
for(i=2; i<100; i++) {
for(j=2; j <= (i/j); j++)
if(!(i%j)) break; // if factor found, not prime
if(j > (i/j)) cout << i << " is prime\n";
}
return 0;
}
OUTPUT:
2 is prime
3 is prime
5 is prime
7 is prime
11 is prime
13 is prime
17 is prime
19 is prime
23 is prime
29 is prime
31 is prime
37 is prime
41 is prime
43 is prime
47 is prime
53 is prime
59 is prime
61 is prime
67 is prime
71 is prime
73 is prime
79 is prime
83 is prime
89 is prime
97 is prime
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