By Muhammad Zidny Nafan 30 January 2012 Looping Structure Initialization the first action before looping started Condition boolean expression for looping Loopings body part of program that will be looped ID: 616978
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Slide1
Looping
By: Muhammad Zidny Nafan
30 January 2012Slide2
Looping Structure
Initialization
, the first action before looping started.
Condition
, boolean expression for looping.
Looping’s body
, part of program that will be looped
Terminator
, the action to terminated loopingSlide3
For
for(exp1; exp2; exp3) statement;
atau:
for(exp1; exp2; exp3)
{
statement1; statement2; …….}
exp1
is
initialization
exp2
is
condition
exp3
is
increment
or
decrement expression
Looping will run if the increment or decrement equal with conditionSlide4
Example 1
Write “Hello World” ten timesSlide5
Struktur While
while (exp) statements;
atau :
while(exp)
{
statement1; statement2; …..;}
exp
adalah boolean expression
Checking for
exp
before statement executed exp will be checked first. If TRUE looping will be processed, if FALSE program will do nothingSlide6
Example 2
Write number 1 to 10Slide7
Struktur do-while
do
{
< statements >;
} while(exp);
Selama nilai exp true maka statement dieksekusi berulang-ulang.Pengetesan exp dilakukan SETELAH meng-eksekusi statement.
Pada konstruksi do-while statement atau blok statement pasti dikerjakan paling sedikit satu kali, karena ekspresi boolean baru diuji pada akhir blok pengulangan
.Slide8
Example 3
penggunaan do-while pada pemilihan menu:
<see in modul>Slide9
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Slide
9
Sums and Products
A common task is reading a list of numbers
and computing the sumPseudocode for this task might be: sum = 0; repeat the following this_many times cin >> next; sum = sum + next;
end of loop
This pseudocode can be implemented with a for-loop
as shown on the next slideSlide10
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Slide
10
for-loop for a sum
The pseudocode from the previous slide is
implemented as int sum = 0;for(int count=1; count <= this_many; count++) { cin >> next; sum = sum + next; }sum must be initialized prior to the loop body!Slide11
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11
for-loop For a Product
Forming a product is very similar to the sum
example seen earlier int product = 1; for(int count=1; count <= this_many; count++) {
cin >> next;
product = product * next
;
}
product must be initialized prior to the loop body
Notice that product is initialized to 1, not 0!Slide12
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Slide
12
Which Loop To Use?
Choose the type of loop late in the design process
First design the loop using pseudocodeTranslate the pseudocode into C++The translation generally makes the choice of anappropriate loop clear
While-loops are used for all other loops when there
might be
occassions
when the loop should not run
Do-while loops are used for all other loops when
the loop must always run at least onceSlide13
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13
Choosing a for-loop
for-loops
are typically selected when doing numeric calculations, especially when using a variable changed by equal amounts each time the loop iteratesSlide14
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Slide
14
Choosing a while-loop
A while-loop is typically used
When a for-loop is not appropriateWhen there are circumstances for which the loop body should not be executed at allSlide15
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Slide
15
Choosing a do-while Loop
A do-while-loop is typically used
When a for-loop is not appropriateWhen the loop body must be executed at least onceSlide16
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16
Debugging Loops
Common errors involving loops include
Off-by-one errors in which the loop executes one too many or one too few timesInfinite loops usually result from a mistake
in the Boolean expression that controls
the loop