sqe(lecture 7)

8/6/2019 SQE(Lecture 7)

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Lines Of Code (LOC) Metrics

Lines of code (LOC) is a software quality

metric used to measure the size of a software

program by counting the number of lines in the text

of the program's source code.

There are two major types of LOC measures:

Physical LOC and Logical LOC.


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Physical LOC is a count of lines in the text of the

program's source code including comment lines.

Logical LOC measure the number of "statements",

but varies according to specific computer languages.

EX: Logical LOC measure for C Programming is the

number of statement-terminating semicolons.


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Example:

for (i = 0; i < 100; i += 1) printf("hello"); /* How

many lines of code is this? */

1. Physical LOC = 1

2. Logical LOC= 23. Comment line=1


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/* Now how many lines of code is this? */

for (i = 0; i < 100; i += 1)

{

printf("hello");

Printf(thank U);

}

1. Physical LOC=6

2. Logical LOC=3

3. Comment line=1


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There are various methods and algorithms within the

same language to count LOC, describe by Jones

(1986)1 Count only executable lines.

2 Count executable lines and data definition or data

manipulation statements.

ex:{

int a;

/* ... */

EXEC SQL SELECT salary INTO :a FROM Employee

WHERE SSN=876543210;

/* ... */

printf("The salary is %d\n", a); /* ... */

}


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3. Count executable lines, data definition, andcomments.

4. Count data definition, comment, and job control

language (scripting language used on IBM

mainframe operating systems to instruct the

system on how to run a batch job or start asubsystem.


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According to Boehm (1981) the LOC counting

method counts lines as physical lines and includes

executable lines, data definitions, and comments.

In Software Engineering Metrics and Models by Conte et

al. (1986), LOC is defined as follows:

LOC is any line of program text that is not a commentor blank line, this specifically includes all lines

containing program headers, declarations, and

executable and non-executable statements.


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When a new software product is released for the firsttime and when a certain LOC count method is

specified.

For example, suppose the, product has a total of50

KLOC, the defect rate for this product during thenext two years is 2.0 defects per KLOC.

For subsequent versions of the product, one needs to

measure the quality of the entire product as well as

the portion of the product that is new.


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Line of code defect rate

At IBM Rochester(U.S) The LOC count is based on

source instruction (Logical LOC includes executable

code and data definition but exclude comments).

Two types of metrics to measure LOC ofnew andchanged source instruction.

1) Shipped source instruction(Current release).(SSI)2) Changed source instruction.(CSI)


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Relation between SSI count and CSI count

SSI (current release) = SSI (previous release) + CSI (new

and changed code instructions for current release)

deleted code (usually very small) changed code (to

avoid double count in both SSI and CSI)


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There are various defect rate metrics per thousandSSI or per thousand CSI are as follows.

(1) Total defects per KSSI (a measure of code

quality of the total product).

(2) Field defects (which are found bycustomers) per KSSI (a measure of defect rate in the

field).

(3) Release-origin defects (field and internal) per

KCSI (a measure of development quality)

(4) Release-origin field defects per KCSI (a

measure of development quality per defects

found by customers)


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Function Point Metric (FP)

Proposed byAlbrecht(1983).

It can be used to easily estimate the size of thesoftware product directly from the problem

specification.

This in contrast to the LOC metric, where the sizecan be determined after the product has fully been

developed.


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Basic idea behind (FP) is, size of the software

product is directly depend on the number of

different functions or features it supports.

The function points are derived using an empirical

relationship based on direct measure ofsoftwares

information domain.

Information domains are defined by.


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Number of external inputs.(EIs).

Number of external outputs(EOs).

Number of external inquiries(EQs).

Number of internal logical files(ILFs).

Number of external interface files(EIFs).


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Number of external Inputs(EIs):

Each data item input by the user. Data items

should be distinguished from users inquiries, such

as Print-account-balance.

Number of external outputs (EOs):

The outputs considered refers to report printed,

screen output, error message produced etc.


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Number of external inquiries(EQs):

number of distinct queries which can be made by

the users. These inquiries are users command which

requires specific action by the system.

Number of internal logical files(ILFs):

Each logical file is counted. A logical file is a groupof logically related data. It can be a data structure.


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Number of external interface files(EIFs):

Interfaces used to exchange information withother systems. Examples of such interfaces are data

files on tapes, disks, communication link with other

system etc.


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Once these data have been collected, a complexity

value should be given for each information domain

after validated by observations over many projects.

Organization that used function point method

developed criteria for determining whether a

particular entry is simple, average, orcomplex.


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Now the function point can be calculated in two steps.

1) The first step is to compute the unadjusted

function points(UFP).

Ex: In case of average information domain value UFP willbe

UFP = (External inputs(EIs))*4 + External outputs(EOs)*5

+ External inquiries(EQs)*4 + Internal logical files(ILFs)*10 + External interface files(EIFs)*7


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2. Second step is to compute the technical complexityfactor(TCF).

The TCF refines the UFP measure by considering 14

other factors based on response to the following

questions.

Does the system require reliable backup and

recovery?

Are specialized data communication required totransfer information to or from the application?

Are there distributed processing functions?

Is performance critical?


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Will the system run in an existing, heavily utilized

operational environments?

Does the system requires on-line data entry?

Does the on-line data entry require the inputtransaction to be built over multiple screens or

operations?

Are the ILFs updated online?

Are the input, output, files, or inquiries complex?


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Is the internal processing complex?

Is the code designed to be reusable?

Are conversion and installation include in the design?

Is the system designed for multiple installation in

different organizations?

Is the application designed to facilitate change and for

ease of use by the user?


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Each of these 14 factors is assign a value ranging

from 0 to 6.

The resulting values are summed yielding total degree

of influence(DI).

The TCF is calculated using the formula

TCF = (0.65 + 0.01*DI)

DI can vary from 0 to 70

TCF can vary from 0.65 to 1.35.

Finally FP= UFP*TCF


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Problem

A system has 12 external inputs, 24 external

outputs, fields 30 different external queries,

manages 4 internal logical files, and theinterfaces with 6 different legacy system(6

EIFs). All of these data are of average

complexity and degree of influence is 46.Calculate FP.

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