•Apps is an abbreviation for application. An app is a piece of software. It can run on the Internet, on your computer, or on your phone or other electronic device.

• Google refers to their online services as apps, but they also sell a specific suite of services known as Google Apps and have an application hosting service called Google App engine.

Google App Engine is a platform for writing your own Web applications and have them hosted on Google servers.

Currently the supported programming languages are Python, and Java.

Google Apps can be found on the Web at www.google.com/a

And Google App Engine can be found on the Web at code.google.com/appengine.

You can serve your app using a free name on the appspot.com domain. You can share your application with the world, or limit access to members of your organization.

App Engine shares resources among multiple applications, but isolates the data and security between each tenant as well.

Your application is able to use some of the Google services, like URL Fetch, to execute processes on its behalf.

Because you can't open ports directly within your application, you have to rely on this service, for example, to request Google to open a port and execute the fetch on a URL for the application.

Easy to get started

Simple app configuration

Automatic Scalability

Reliability

Security

. With App Engine you write your application code, test it on your local machine and upload it to Google with a simple click of a button or command line script.

Once your application is uploaded to Google , then google host and scale your application.

The app engine takes care of all the maintenance so you can focus on features for your users.

You can create an account and publish an application that people can use right away at no charge from Google. When you need to use more resources, you can enable billing and allocate your budget according to your needs.

Each App Engine application can consume a certain level of computing resources for free, controlled by a set of limits(eg, Google App Engine requires a Google account to get started, and an account may allow the developer to register up to 10 applications.)

Developers who need resources above these free limits can switch to a paid app using Google Checkout to set a daily resource budget.

When you convert to a paid app you will spend a minimum of $2.10/week. This allows you to purchase additional resources when needed.

App Engine will always be free to get started, and after you've created a paid app, all usage up to the free limits will remain free.

Automatic scaling is built-in with App Engine.

Your applications can take advantage of the same scalable technologies that Google applications are built on.

All you have to do is write your application code and the app engine does the rest. No matter how many users you have or how much data your application stores, App Engine can automatically scale to meet your needs.

The same security, privacy and data protection policies we have for Google's applications applies to all App Engine applications.

There are measures to protect your code and application data.

The Secure Data Connector (SDC) ensures that private data is securely accessible to your Google App Engine application.

Limit resource usage

Limit 1000 files per app, each at most 1MB Hard time limit of 10 seconds per request Most requests must use less than 300 msec CPU time Hard limit of 1MB on request/response size, API call size, etc. Quota system for number of requests, API calls, emails sent, etc

Developers have read-only access to the filesystem on App Engine.

App Engine can only execute code called from an HTTP request

Does not support 'naked' domains (without www) like http://example.com.

A process started on the server to answer a request can't last more than 60 seconds.