Looping Control Structure.

1. PRESANTATION ON
“Looping control structure”
GUPTA HARSH
13ME030

2. Introduction of loop
• A loop is a programming structure that allows
an action to repeat until the program meets a
given condition.
• After each iteration of a loop, the loop checks
against a loop control expression to see if the
program met a the given condition. If it did,
the loop stops. If not, the loop moves on to
the next iteration.

3. CONTINUE…
• Loop: a control structure that repeats a group
of steps in a program
• C loop control statements
• Two types of control statement….. They are:-
Exit control loop and
Entry control loop

4. Exit Control loop
• In exit control loop, the
body is executed first and
then the condition is
checked.
• In exit control loop the
body is executed
at least once.

5. Entry Control loop
• In entry control loop,
the condition is checked
first and then body is
executed.
• In Entry control loop
the body is not
executed at all if the
condition is false.

6. Looping…
• ‘C’ language provides following looping
structures:-
1. WHILE
2. DO-WHILE
3. FOR

7. WHILE LOOP
– Of the three different loop structures offered in C, while-
loops are conceptually the simplest.
– Resembles if-statement, but does not have an else.
– Conceptually, keep executing the loop body again and
again till the condition is true.
– Loop terminates when the loop condition becomes false.
– Note that the truth of the loop condition is not checked
constantly between every statement in the loop body, but
only at the beginning of the loop, and then again between
the repetitions of the loop body
– Condition may be temporarily false during the loop, but
become true again before it is checked

9. DO-WHILE LOOP
– The second type of loop offered in C is the do-while.
– Clearly the least commonly used of the three: one famous
study of real world programs revealed that out of all loops
in them, only 1% are do-while.
– Do-while behaves exactly the same way as the while-loop,
but is guaranteed to execute its body at least once before
it starts looking at the loop condition.
– The possibility of executing the loop body zero times
does not exist, even if the condition is initially false
– do-while is most useful in situations where testing
the condition simply does not make any sense until
the loop body has been executed once

11. FOR LOOP
– The third type of loop structure in C is suitable for
the common task of iterating through the values of
a range of integers, one value at the time.
– For example, go through the numbers from 1 to 100.
– The for-loop header defines this range, and the loop
body contains the statements you execute for each
value.
– To define an integer range, you need to define three
things: where it begins (1), where it ends (100), and
the step size between the consecutive values of the
range (1)

12. CONTINUE…
– It is not a coincidence that the header of a for-loop
consists of three parts, for the three things that
define a range.
– We can still use while like in countdown, but using a
for-loop makes it clear that we are going through a
range.
– It is not a coincidence that the header of a for-loop
consists of three parts, for the three things that
define a range.
– We can still use while like in countdown, but using a
for-loop makes it clear that we are going through a
range.

13. Flowchart of FOR LOOP
for( initializing list;condition; updation)

14. BREAK STATEMENT
• Remember the break keyword that we used
to stop a switch statement from executing
more than one statement?
• break can also be used to exit an infinite
loop
• But it is almost always best to use a well-
written while loop.

15. CONTINUE STATEMENT
– Continue is a statement similar to break, but
instead of jumping out of the loop altogether, it
jumps to the next round of the loop, skipping the
rest of the body
– Most commonly used to skip some of the values
inside the range for which the loop doesn't need
to do anything