WhatsApp Messenger is a cross platform messaging application available for Android, Blackberry, iPhone and Nokia phones. The app works using the internet connection (3G, WiFi or mobile data plan) of your phone. Android, Blackberry and iPhone users can send and receive pictures, audio notes, and video messages too.

WhatsApp's main screen

Installation & Download

*Installing the app is a really simple procedure.

1. Download the app either from the Android Market or directly from the WhatsApp website.
2. Accept the terms of license agreement terms.
3. Select your country and enter your own number.
4. Enter a display name of your choice. This is used only when contacting iPhone users.

Thats all. Now the app will look for contacts in your address book and will add them to your WhatsApp contacts list if any of those numbers have WhatsApp installed on their phones.

WhatsApp is now ready to be used.

Adding a New Contact

1. Add the contact to your phone address book.
2. Open WhatsApp.
3. Click on the pen icon on the top right of the screen.
4. Press menu button and then click on refresh.
5. WhatsApp will look for contacts in your address book using WhatsApp and will add them to your WhatsApp contacts list.

Features

1. Unlimited use. There is no restrictions on sending and receiving data or messages. Also there are no charges even when the other person is in some another country. You can chat with your friends all over the world.
2. Group chat feature is also available. Open WhatsApp, then press Menu and tap Group Chat. You can choose a group subject and group participants; one group can contain up to five people.
3. WhatsApp does away with the need for PINs and usernames; you only need the phone number of the person you need to add to your WhatsApp contact list.
4. Always on. There is no need to log in. You will immediately receive a notification for any message sent to you even if the app is not open. (If you are using a task killer, unselect WhatsApp app from the list of apps you choose to kill.)  In case you turn off your phone, your message will be stored by WhatsApp and you will receive the message whenever you turn on the phone.
5. You can e-mail chosen chat history.
6. You can choose a wallpaper to set as the background in the app. WhatsApp has a background wallpapers collection available for download too.
7. You can set custom notification tones.
8. Status updates are supported.
9. Facebook pictures of contacts are imported.

User Interface

When you open the app, the screen will display the summary of the most recent chats sorted by time. Chats from a contact are grouped together.

The Facebook picture of the contact is displayed on the left and the time stamp on the right. All conversations are displayed in bubbles, like the stock display of the iPhone.

whatsapp chat interface

You will notice that there are two ticks before every message sent; the first tick indicates the message has been successfully sent, while the second one indicates the message has been successfully received.

To enhance the chatting experience, WhatsApp comes with a lot of smileys. Also, when you are chatting with any contact, you can see the status of the person on the top left below the contact name, which also shows when the contact is typing something. You can update your current status to Available, Busy, At School, or whatever you like.

Pricing

The app is available as free for use for a period of one full year, and then $1.99 per year after that. All the features of the app are available even during the free use, and there are no advertisements of any sort.

Support and Storage

The app works on all Android versions. It will open quickly and run smoothly on most of the phones. I did not come across any force close errors. However, older and low end Android phones may find this app to take up a lot of their memory: the app takes up about 7 MB of your internal storage space, and cannot be moved to the SD card. While running in the background the app uses up around 16 MB of your memory.