1 Lecture 14 Chapter 6 Looping Dale/Weems/Headington.
27
1 Lecture 14 Chapter 6 Looping Dale/Weems/Headington
-
date post
21-Dec-2015 -
Category
Documents
-
view
218 -
download
0
Transcript of 1 Lecture 14 Chapter 6 Looping Dale/Weems/Headington.
1
Lecture 14
Chapter 6
Looping
Dale/Weems/Headington
2
Chapter 6 Topics
While Statement Syntax Count-Controlled Loops Event-Controlled Loops Using the End-of-File Condition to Control
Input Data Using a While Statement for Summing and
Counting Nested While Loops Loop Testing and Debugging
3
Revision of Selection
What construct is used in C++ to narrow down our range of values?
What is the rule for matching else constructs to if constructs?
What is the danger in using an if followed by another if?
For testing selection control structures, should we use white box testing or black box testing?
4
A loop is a repetition control structure.
it causes a single statement or block to be executed repeatedly
What is a loop?
5
Two Types of Loops
count controlled loops
repeat a specified number of times
event-controlled loopssome condition within the loop body changes and this causes the repeating to stop
6
While Statement
SYNTAX
while ( Expression )
{ .
. // loop body
.
}
NOTE: Loop body can be a single statement, a null statement, or a block.
7
When the expression is tested and found to be false, the loop is exited and control passes to the statement which follows the loop body.
WHILE LOOP
FALSE
TRUE
bodystatement
Expression
8
an initialization of the loop control variable
an expression to test for continuing the loop
an update of the loop control variable to be executed with each iteration of the body
Count-controlled loop contains
9
int count ;
count = 4; // initialize loop variable
while (count > 0) // test expression
{
cout << count << endl ; // repeated action
count -- ; // update loop variable
}
cout << “Done” << endl ;
Count-controlled Loop
10
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
count
11
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
count
4
12
Count-controlled Loop
int count ;
count = 4;
while (count > 0) TRUE
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
count
4
13
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4
count
4
14
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4
count
3
15
Count-controlled Loop
int count ;
count = 4;
while (count > 0) TRUE
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4
count
3
16
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3
count
3
17
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3
count
2
18
Count-controlled Loop
int count ;
count = 4;
while (count > 0) TRUE
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3
count
2
19
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3 2
count
2
20
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3 2
count
1
21
Count-controlled Loop
int count ;
count = 4;
while (count > 0) TRUE
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3 2
count
1
22
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3 2 1
count
1
23
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3 2 1
count
0
24
Count-controlled Loop
int count ;
count = 4;
while (count > 0) FALSE
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3 2 1
count
0
25
Count-controlled Loop
int count ;
count = 4;
while (count > 0)
{
cout << count << endl ;
count -- ;}
cout << “Done” << endl ;
OUTPUT
4 3 2 1 Done
count
0
26
User has to give 100 blood pressure values observed for a patient
Use a while loop to read the 100 blood pressure values and find their average
Count-Controlled Loop Example
27
int thisBP ;int total ;int count ;
count = 0 ; // initialize
while ( count < 100 ) // test expression{ cin >> thisBP ;
total = total + thisBP ; count++ ; // update
}
cout << “The average = “ << ((float) total)/100.0 << endl ;
