**Repetition**can be

**implemented**

**using**constructs like the

**repeat loop,while loop and if...then...goto... loop.**The

**repeat loop**is

**used**to

**iterate**or

**repeat a process**or

**sequence of processes until some conditional becomes true.**

**It has the general form:**

**Repeat**

Process 1

Process 2

..............

...............

Process N

*until*proposition

Here is an example:

Repeat

Fill water in kettle

*until*

**Kettle**is full

The process is 'Fill water in

**Kettle'**,the proposition is '

**Kettle**is full'.

The repeat loop does some processing before testing the state of proposition.

**What happens though if in the above example the Kettle is already full?**If the

**Kettle**is

**already full at**the

**start**of the

**Repeat loop**,then

**filling more water will lead**to an

**overflow.**This is a

**drawback of Repeat construct.**

**In such case the while loop is more appropriate.The above example with the while lopp is shown as follows:**

*while*

**Kettle**is not full

fill water in

**Kettle**

Since,the

**decision about**the

**Kettle being full or not is made before filling water**,the

**possibility**of an

**overflow is eliminated.The while loop find out whether some condition is true before repeating a process or a sequence of processes.**

If the

**condition is false**,the

**process or the sequence of process is not executed**.The general form of while loop processes is not executed.

__The general form of while loop is :__**while proposition**

*begin*

Process 1

Process 2

...............

...............

Process N

*end*

The if...then...goto is also used to repeat a process or a sequence of process until the given proposition is false.In the Kettle example,this construct would be implemented as follows:

So long as the proposition '

**Kettle**not full' is true,the process 'fill some water in

**Kettle**' is repeated.

The general form of if...then...got.. is:

Process 1

Process 2

..............

..............

Process N

*if*proposition

*then goto*Process 1

###
__Termination:__

The definition of algorithm cannot be restricted to procedure that eventually finish.Algorithms might also include procedures that could run forever without stopping.Such a procedure has been called a computational method by Knuth or calculation procedure or algorithm by

###

**Kleene.**However,**Kleene**notes that such a method must eventually exhibit 'some object'.**Minsky (1967)**makes the observation that,if an algorithm has not terminated,then how can the following question be answered:"Will it terminate with correct answer?".Thus the answer is :undecideable.It can never be known,nor can the deisgner do an analysis beforehand to find it out.The analysis of algorithms for their likelihood of termination is called termination analysis.###
__Correctness:__

__Correctness:__

The prepared algorithm need to be verified for its correctness.Correctness means how easily its logic can be argued to meet the algorithm's primary goal.This requires the algorithm to be made in such a way that all the elements in it are traceable to the requirements.

Correctness requires that all the components like the data structure,modules,external interfaces and module interconnections are completely specified.

In other words,correctness is the degree to which an algorithm performs its specified function.The most common measure of correctness is defects per Kilo Lines of codes(KLOC) that implements the algorithm,where defect is defined as the verified lack of conformance to requirements.

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