good programming skills

7/28/2019 Good Programming Skills

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January 20, 2011 TCS SASTRA PUBLIC

Good Programming Skills


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January 20, 2011TCS SASTRA Public2

To develop Skills to write programs that are more understandable,

following good programming practices

Code Refactoring to improve quality of code

Introduction to Defensive Programming

Objective


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The gap between the best software engineering practice and the average practice is very wide -

perhaps wider than in any other engineering discipline. A tool that disseminates good practice would be

important. - Fred Brooks in " The Mythical Man-Month"

The Importance of Good Programming Skills

In a survey in TCS, 89 Project Leaders & Group Leaders

ranked important skills for entrants to ILP as follows:

1. Good Programming Practices

2. Process Mindset3. Communication Skills

4. Adaptability & Teamwork

5. Concern for Quality

6. Knowledge of Core Computer Science Topics


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A true project experience

A TCS project well appreciated by client for

Correctness

On Time Delivery

Good project Managements

Customer requested enhancements for the well delivered product but later complained

that enhancement requests were pending with TCS for months.

Root Cause : Poor Understandability of code

Improve Understandability of the code you write !


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Self-review is easier leading to less defects

Debugging takes less time

Another developer will find it easier to maintain your program

Improving Understandability - Advantages


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1.Follow Standards

All team members following the same standards, makes more understandable your code

Follow the ILP coding guidelines and build this habit.

Each project will have its own coding guidelines based on TCS coding guidelines


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A Problem

An employee less than 1 year of experience is a fresher.1-2 years of experience is a

Junior Engineer.2-5 is a lead engineer.5-8 is a manager.8-15 a senior manager and 15

and above General manager. A fresher is eligible only for basic salary. A Junior Engineer

is eligible for HRA as well. A lead engineer is eligible for HRA and LTA. All the managersare eligible for Medical allowances also. General managers are eligible for special

allowance along with all the other allowances. Calculate the salary of an employee.

HRA is 10% of basic salary, LTA is 2%,Medical allowance 15% and special allowance is

20% of basic salary.


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Can you understand this ?


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A routine should perform one and only one operation.

Descr ibe everyth ing the rout ine do esIn the routine's name

The routine has too many parameters (9) , parameters >7 is not recommended

Some of routines parameters unused (age)

The routines parameters are poorly ordered

Avoid unnecessary parameters (allow1,allow2,allow3,allow4)

2. Refactor to Improve Understandability

Write Programs for People First, Computers Second


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The routines name doesnt convey anything(getitwork21( ))

The routine doesn't have a single purpose (It finds the employee type and computes salary)

The routine has a bad layout. (The physical organization of the code on the page givesfew hints about its logical organization)

The variable/parameter names not meaningful. (allow1,e,Type)

The routine isn't documented.

The routine doesn't defend itself against bad data. (If basic salary is given as negative,it doesn't throw any error )


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Simplify design and code - Start with interface

With people first in mind, refactor the interface to meet the standards

discussed

void getItwork21(String Type,int allow2,int bSAL,int allow1,int e,int allow3,

int allow4,int age,String name)

Better interfaces Better routine names Less / only essential

parameters


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Refactoring the function body

Better routine name

Single Task

Better layout


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Better variable names


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We did code refactoring to improve understandability,

We can also refactor code to

- remove duplicate code- enhance robustness

- adaptability,

- re-use or to apply some creative insight.

Refactoring -

Saves maintenance costs

Makes it more comfortable for the maintainer.

These factors must be balanced with the effort and time required for

the refactoring.


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Specific Refactorings

Data-Level

Statement-Level

Routine-Level

Source: Code Comp lete, Second Edit ion b y Steve McConn el l


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Data-Level

Replace a magic number with a named constant

Rename a variable with a clearer or more informative name

Move an expression inline

Replace an expression with a routine

Introduce an intermediate variable

Convert a multiuse variable to multiple single-use variables

Use a local variable for local purposes rather than a parameter


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Statement-Level

Decompose a boolean expression

Move a complex boolean expression into a well-named boolean function

Consolidate fragments that are duplicated within different parts of a conditional

Use break or return instead of a loop control variable Return as soon as you know the answer instead of assigning a return value withinnested if-then-else statements


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Routine-Level

Extract routine/method

Move a routine s code inline

Substitute a simple algorithm for a complex algorithm

Add/Remove a parameter

Separate query operations from modification operations

Combine similar routines by parameterizating them Separate routines whose behavior depends on parameters passed in


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Refactor safely

Refactor one at a time

Save the code before refactoring

Retest after each refactoring

Add test cases

Review the changes

Keep refactoring small

Make frequent checkpoints

Adjust your approach depending on the risk of the refactoring

Source: Code Com plete, Second Edit ion by Steve McConnel l


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Every function must provide its purpose

For java, Javadoc is a good choice for documentation as

- it is generally adequate

- easy to understand and use

- it is popular

3. Comment Judiciously


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Comment jud ic ious ly Sample method comment

/**

Calculates the Salary based on years of experienc e and b asic salary

@param experienc eYears - the years of experience of an emplo yee

@param basicSalary - the basic salary of an emp loyee

@return the tota l salary o f an emp loyee

*/

publ ic stat ic do ub le calcSalary(int experienceYears, int basicSalary){

Improving Understandability


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Construction accounts for about 75 percent of the errors on small projects

and 50 to 75 percent on medium and large projects. Any activity that

accounts for 50 to 75 percent of the errors presents a clear opportunity for

improvement

-Steve McConnell in Code Complete

Improving code correctness Why?


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Defensive programming

Similar to defensive driving style!

Check the values of all data from external sources

Check the values of all routine input parameters

Check all return values from all methods to be in the acceptable range

Always have an otherwise or default clause in conditional statements

to catch those cases that are not expected and so not processed

Ensure that your code is not used inappropriately Sourc e: Code Comp lete, Second Edit ion by Steve McConnell

Improving Code Correctness - Defending Against Bad data


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Why defensive programming helps ?

Programming is complex and a major challenge.

With the best of intentions, we may still expect problems

Defensive programming techniques help us disc over a defect asclos e as feasible.

Defensive Programming


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Code Comp lete, Second Edit ion by Steve McConnel l

Good Programm ing Pract ices & Ski l ls by Abbas K. Sutarwala

References


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January 20, 2011 TCS SASTRA PUBLIC

Happy Learning!

good programming skills

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