I am Hammad Maqbool

State Diagram is one of the UML Diagram which use to show the dynamic behavior of the system.

We use the state diagram only when any object of the system changes its states in the life. This diagram helps us in representing how an object goes through from one state to other and what are the factors which make the object to transit from one state to other, When object move from one state to other if we have options to go in different states so what state an object chose to move forward and where the chosen state take the object.

there is no Rocket science involve in the state diagram, you being an object of the person class have a unique name lets say "John" and you in your whole life make keep transiting through different states up different factors.

The factor of feeling sleepy transit you to the sleeping state, the factor of  being hungry transit you to the eating state, the factor or the environment which you hate transit you to the Angry state.

This UML Diagram only represent your transitions from one state to another in a flow.

Being a human if you start to make your life state diagram I don't think you can predict all the states through which you will pass in future. Because it depends on the environmental factors and lots of other external factors but the GOD knows your state diagram very well isn't it?

same like this when you develop a software, It could be the bundle of classes, and there would be lots of objects of different classes, Now the object of the class do not know the states from which or to which it will transit in the whole life, But the creator of the object in this case that's you being a programmer or Software Engineer knows very well the states from which an object going to pass in different situation so according to your knowledge you make this state diagram.

Now The objects in the software are not like Humans they some times change the states but most often they are assign to a task (specific task) and by remaining in a single state the keep performing those tasks and dies at the end just after completing the assigned task this is the case in most of the objects in software you don't have to draw state diagram for these kind of software just think if the software is not changing the state in the whole life what is the purpose of making state diagram.

If there are some objects who are assigned to some task but change the state on factors then you have to make a state diagram for it. 

I have given the examples of objects changing the states, may be the example of Easypaisa in the video will be beneficial to understand what I have describe in the whole article till now.

I will recommend you to watch the video now it will help you to clear the concepts.

This is the most commonly in use diagram of software engineering by UML used to represent the flow of activites in a specific manners and making of decission in the flow.

initial stat, activity, fork, merge diamond and final state are the mose common things in the activity diagram of UML.

This is the UML activity diagram tutorial in hindi and udrdu. Watch the video lecture of 20min and learn it. 

UML activity diagram symbols or say Activity diagram notations are the things which make the difference between and activity diagram in software engineering and simple workflow diagram in business.

UML make a standard set of notations for the every diagram in software dsign, same for the activity diagram.

We have symbols to represent every thing in diagrm explained in very detail the above five video tutorial of the activity diagram.

The diagram shown in the picture above is also explained in the video.

This is the most confusing thing until you don't know how to make the relationships between the classes. 

If you know the best approach to make relation in class diagram UML trust me this the most easy work to do.

The best approach to make relation in Class Diagram is use the binary approach as described in the video.

If you use this approach you focus on a single class every time instead of focusing on the whole diagram making.

One you have binary relations you have a class diagram

Click below to download the slides in PDF format which are presented in the above video

Student often found it difficult to understand and difficult to draw class diagram, but I think if you know the core concepts of class diagram it is not some thing that much difficult. Lets  have a discussion at it.

Anything from the real world which we want to map in software engineering for making a software that can be a class. I think examples are best part to understand tricky things lets have a look at example.

For Example: I am planing to make a software i.e as "Hospital Management System" now the next part is I will collect the requirements for it and think over it what will be the real world objects and things participate in this software. What first come into the mind? 

• Patient
• Patient Record
• Doctor

And lots of many other things I am not going to write each and every thing, now these can be the classes. 

a Patient can be a class same for other two.

I think concept is cleared about what is class and from where it comes now it will be easy to understand what is class diagram, that simple collection of classes linked with each other known as class diagram.

Now there can be many types of associations between the classes.

I think theoretical concepts are more than clear now lets have a look at practical representation of the class