virsioncontrol

Need of  VCS

Version control assist you to evaluate documents, become aware of differences, and merge

the adjustments if wished previous to committing any code. Versioning is also a tremendous manner to keep track of utility builds

being able to discover which model is presently in development, QA , and manufacturing. Also, while new developers be a part of the crew,

they are able to easily download the modern version of the utility to their nearby surrounding the use of the model control device and

able to keep track of the version there are presently running. During improvement

you could additionally have completely unbiased code variations in case you chose to keep special improvement ,

effort separate. When equipped, you could merge the document to create a very last running version

Models of VCSs

Centralized Version control

Benefits:-

1.It is easy to understand.

2.you have more control over users and access(since it served from one place)

3.More GUI and IDE clients

4.Simple to get start commenced

Drawbacks:-

1.Dependent on access to the server

2.Hard to mange a server and backups

3.It can be slower because every command connects to the server

4.Branching and merging tools are difficult to use

Distributed version control

Benefits:-

1.It's speedy

2.No server essential

3.More powerful and exact exchange tracking, which means that less conflicts

4.Branching and merging is more dependable, and therefore

Drawbacks:-

1.The distributed model is harder to understand.

2.It’s new, so not as many GUI clients.

3.The revisions are not incremental numbers, which make them harder to reference.

4.It can be easier to make mistakes until you are familiar with the model.

GIT and GIT HUB

Git is a free and open source distributed version control system designed to handle

everything from small to very large projects with speed and efficiency

GitHub is a web-based Git repository hosting service, which offers all of the distributed

revision control and source code management functionality of Git as well as adding

its own features

GIT commands , commit, push

commit: adding changes to the local repository

push: to transfer the last commit to a remote server

Git commit: "records changes to the repository" while Git push "updates remote

refs along with associated objects”. So that first one is used in connection with

your local repository, while the latter one is used to interact with a remote

repository

Staging area and GIT directory

when you work on your project making changes you are dealing with your project's working

directory. This is the project directory on your computer's file system. All the changes

you make will remain in the working directory until you add them to staging area( via git add

command) .the staging area is best described as preview of your next commits. Meaning,

when you do a git commit, git will take the changes that are in the staging area and make a new commit

out of those changes. One practical use of the staging area is that it allows you to fine-tune your commits. You can add and remove changes from staging area until you are satisfied with how your

Next commit will look like , at which point you can do git commit.  And after your commit your changes they go in to .git/Objects directory where they are saved as commit, blob and three objects.

GIT workflow

Git workflow defines a strict branching model designed around the project release. This work flow doesn’t add any new concepts or commands beyond what’s required  for the Feature Branch flow . Collaboration is often about branching workflow. Thinking ahead on how you will interview commit trees will help you minimize integration bugs and support your release management strategy.

·        Nimal works on his feature

In his local repository, Nimal can develop features using the standard Git commit process:

Edit, stage and commit . Remember that since three commands create local commits, Nimal

Can repeat this process as many times as he wants without worrying about what’s going on

The central repository.

·        Anne works on her feature

Meanwhile, Anne is working on her own feature in her own local repository using the same

Edit/stage/commit process. Like Nimal ,she doesn’t care what’s going on in the central repository, and she really doesn’t care what Nimal is doing in his local repository, Since all local repositories  are private.

Benefits of CDN

Companies that witness a huge traffic on their website on daily basis can use cdn to their advantage. When large number of users at the same time access a web page on same specific content such as video, a cdn enables that content to be each of them without delay. There are some few of benefits using a cdn for your website

·        Your server load will decrease

·        Content delivery become faster

·        Segmenting your audience become easy

·        Lower network Latency and packet loss

·        Higher Availability and better usage analytics

·        Offer secure storage capacity foe content

Differences between CDNs and Web Hosting

Web hosting is used to host your website on a server and let users access it over the internet. A content delivery network is about speeding up the access/delivery of your website’s assets to those users.

Web Hosting normally refers to one server. A content delivery network refers to a global network of edge servers which distributes your content from a multi-host environment.

Traditional web hosting would deliver 100% of your content to the user. If they are located across the world, the user still must wait for the data to be retrieved from where  your web server is located. A CDN takes a majority of your static dynamic content  and servers it from across the globe, decreasing download times. Most times, the closer the CDN server is to the web visitor , the faster assets will load for them.

Identify free And Commercial CDNs

               CDN is a geographically distributed network for proxy servers and their data centers. The goal is to provide high availability and high performance by distributing the service spatially relative to end users

               CDN server a large portion of the internet content today, including web objects ,  downloadable objects , applications , live streaming media, and social media sites.

Requirements for virtualization

               There is a gap between development and implementation environments

ü  Different platforms

ü  Missing dependencies , frameworks/ run times

ü  Wrong configurations

ü  Version mismatches

Hardware virtualization

OS level virtualization (desktop virtualization)

Application level virtualization

Containerization (also OS / application level)

Other virtualization types

Pros and Cons of different virtualization techniques in different levels

               Pro :-

Ø  Efficient resource utilization:

Virtualization enables business  to get the most out of  their investments in hardware  and

               Resources.

              

Ø  Reduced IT costs:

Virtualization helps business reduce costs in several way, according to Mike adams who is senior director of cloud platform product marketing at VMware

v  Capital expenditure savings

v  Operational expenditure savings

v  Data center and energy-efficiency savings

Con:-

Ø  Not all hardware or software can be virtualized

Ø  The upfront costs are hefty

Popular implementations and available tools for each level of virtualization

     Plotly

     Tableau

     FusionCharts

     Datawrapper

     Sisense

     Highcharts

Hypervisor and it’s role

A hypervisor is a process that separate a computer’s operating system and applications from the underlying physical hardware. Usually done as software although embedded hypervisors can be created for things like mobile devices. The hypervisor drives concept of virtualization by allowing physical host machine to operate multiple virtual machines as guests to help maximize the effective use of computing resource such as memory, network bandwidth and CPU cycles.

              

How emulation is different from VMs

               Virtual machines make use of CPU self-virtualization , to whatever extent it exists , to provide a virtualized interface to the real hardware. Emulators emulate hardware without relying on the  CPU being able to run code directly and redirect some operations to a hypervisor controlling the virtual container.

VMs vs Container

VMs	Containers
heavyweight	Lightweight
Limited performance	Native performance
Each VM runs in its own OS	All containers share the hosts OS
Hard ware level virtualization	OS virtualization
Startup time in minutes	Startup time in milliseconds
Allocates required memory	Requires less money space
Fully isolated and hence more secure	Process-level isolation , possibly less secure

Advantage of VMs:-

     All os resources available to apps

     Established management tools

     Appliance upgrade , patches and bug fixes

     Testing and support tools

     Better known security tools

     Supported platform for PIN safe deployment

Disadvantage of VMs:-

     VM type may not be part of organization standard

Advantage of containers:-

     Less code to transfer, migrate, upload workloads

     Reduced IT management resources

     Quicker spinning up apps

     Reduced size of snapshots

Disadvantage of Containers:-

     Data storage is intricate

     The container ecosystem is split

     Graphical applications don’t operate well

Introduction to the frameworks

Declarative programming is a programming paradigm that express the logic of computation without describing its control flow. Its a program

on a higher level of abstraction than imperative programming. Declarative programming is necessary would be in web development when you

are working with framework. Imperative programming is programming paradigm that uses statements that change a program's state. Imperative programming

is necessary would be in the engineering of algorithms and other low level necessities.

Both function and procedures are subroutines that are reused prebuilt block of code. The distinction between them is function return a value

,and procedures don’t. More specially, function are built for having lower side effect and always produce same output when give same input.

In addition function are usually concerned with higher level ideas and concepts. Procedures on other hand don’t have any return value, their

main goal is to complete a given task and cause a desired side impact. A great example is procedure is a loop. The loop main goal is to cause side effect

and doesn’t return a value in of itself.

Lambda calculus is a framework and was developed to study computations with functions. Lambda calculus is a formal system in mathematical

logic for expressing computation based on function abstraction and application using variable combining and substitution .

Lambda expression can be passed around as if it was an object and executed on demand. Enable to treated functionality as method argument, or

code as data. A function can be created without belonging to any class. Lambda expressions provide that functionalities.

A functional side effect is when a function changes two way parameter or a nonlocal variable. It occurs  when the function changes. Either one of

is parameters or a global variable. The lack of side effect makes it. Easier to do formal verification of a program. Functional language as Standard ML,

Scheme and Scale don’t restrict side effects, but it customary for programmers to avoid them

Referential Transparency is a property of a part of program or programming language . This mean that the program's behaviour isn’t changed weather

the input used is reference or an actual value that the reference is pointing to

Features of OOP:

               1.OBJECT :-

                              Object is a collection of wide variety of entities. Object takes space in the memory. Objects are blueprint of classes. When

                              program is executed, object communicates by sending messages to one another. Each object contain data and code to

                              manipulate the data. Object can interact without having realize information of every other data or code.

               2.CLASS :-

                              Class is collection of objects of similar type. Once class is defined, we can create any number of objects belonging

                              that class.

              

               3.ENCAPSULATION :-

                              It is the process of grouping related attributes and methods together, giving a name to the unit and providing an interface

                              for outsider to communicate with the unit.

               4.INFORMATION HIDIND :-

                              hide certain information or implementation decision that are internal to the encapsulation structure

               5.ABSTRACTION :-

                              It is the process of removing characteristics from something in order to reduce it to a set if essential characteristics that is

                              needed for the particular system.

              

               6.POLYMORPHISM :-

                              Poly refer many. So polymorphism as the name suggest is certain item appearing in different forms of way. That making

                              a function or operator to act different forms depending on the place. They are represent as polymorphism.

Event driven programming is programming paradigm in which the flow of the program is determined by events such as user action ,sensor outputs

or messages from other programs or threads. Event-driven programming is the dominant paradigm used in graphical user interfaces and other

applications that are cantered on performing certain actions in response to user inputs. This is also true of programming for device drivers.

Markup language is used to control the presentation of data like "represent the username as bullet list or data table".Markup language don’t executed or

used to perform actions but they are used to structure data, identify data or present data.

Scripting language that aren't compiled , more like interpreted at a runtime. Its like file containing instruction for a computer to follow

to carry out task

A compiled language is the proper and formal language that has been designed to allow programmers to communicate instructions to a computer.

It is used to create programs

A virtual machine (guest) is a program that acts as a virtual computer. It runs on your current

operating system (host) and provides virtual hardware to guest OS. The guest OS runs in a window

on your host OS, just like any other program on your computer. From the guest operating system's perspective, the virtual machine is real, physical computer.

1.Reproduce the bug

                              Finding a series of actions that consistently reproduces a bug  is always the first step to debugging

2.Get familiar with the source panel UI

                              DevTools provides lot of different tools for different task , such as changing css ,profiling page load performance , and

               monitoring network request. The source panel is where you debug JavaScript

3.Pause the code with breakpoints

                              A common method for debugging a problem like this is insert a lot of console.log() statements into the code, in  order to

inspect values as the script executes

4.Step through the code

               One common cause of bugs is when a script executes in the wrong order. Stepping through your code enables you to walk through your code

               extension, one line at a time, and figure out exactly where its executing in a different order than you expected

5.Set a line of code breakpoint

               Line-of-code breakpoints are the most common type of breakpoint. When you have got a specific line of code that you want to pause on,

use line-of-code breakpoint

6.Check variable value :

               The value attend1,attend 2, and sum look suspicious. They are wrapped quotes, which means that there are string. This is good hypothesis

for the explaining the cause of the bug.Now its time to gather more information. DevTool provides  a lot of tools for information. DevTools

provides a lot of tools for examining variable values.

6.Apply a fix

               You have found a fix for the bug. All that’s left is to try out fix by editing the code and re-running the demo. You don’t need to leave

DevTools to apply the fix. You can edit JavaScript code directly within the DeveTools UI

Real case Tool can be separated into 3 types, depending on where in the development process they are most involved in:

               upper-support analysis and design phases.

               Lower-support coding phase

               integrated-also known as I-CASE support analysis, design and coding phases

workbenches:

               collection of tools that together support

               process workflows

               one or two activities where an activity is a related collection of tasks

                commercial ex:

                              PowerBuilder

                              Software Through Pictures

                              Software Architecture

Environments

               Support the complete software process or, at least , large portion of the software process.

               Normally include several different workbenches which are integrated in some way.

Framework -

A framework is a real or conceptual structure intended to serve as a support or guide for the building of something that expands the structure into something useful. Frameworks enable development of a project or solution to a specific problem. Frameworks are ready-to-use packages.

Library –

Library is a collection of precompiled routines that a program can use. Sometimes called modules. You can link that a many programs do not need to explicitly. The Library code that has already been written by other developers. A library performs specific, well-defined operations.

Plug-in-

A plug-in is an element of a software program that can be added to provide support for specific features. For example if you wanted to watch a video on a website, you may need plugin to play it because your browser doesn’t have the tools it needs.

When you call a method from a library, you are in control. But with a framework. In a framework, all the control flow is already there and there are many predefined white spots that we should fill out with our code. A framework is normally more complex. A framework can contain libraries. A framework will usually include many libraries to make your work easier.

The main difference between plugin and library is that a plugin is an extension that improves the capabilities of an application while a library is a collection of classes and functions that helps to develop a software.