The ipad

Introduction to the ipad

At this present moment the ipad come in three different basic configurations, extra choices can be the size of internal storage 18gb 32gb 64gb and their connectivity, WiFi cellular or 3G. The original ipad is no longer available, however apple sold 15 million prior to the introduction of the ipad2

Three types of ipad

Screen & resolution

ipad1    9.7-inch 1024x768 resolution at 132 pixels per inch (ppi)
Mini     7.9-inch 1024x768 resolution at 163 pixels per inch (ppi)
ipad2    9.7-inch 1024x768 resolution at 132 pixels per inch (ppi)
ipad      9.7-inch  2048x1536 resolution at 264 pixels per inch (ppi)

Therefore all screen have the same aspect ratio 4 by 3.
All have multi-touch display

Processor

ipad1    Apple A4

Mini     Dual core A5

ipad2    Dual core A5

ipad      Dual core A6x with quad core graphics.

OS

ipad1    iso 5.1
Mini     iso 6/7
ipad2    iso 6/7
ipad      iso 6/7

Environmental sensors

ipad1    Accelerometer, ambient light sensor, magnetometer,

Mini     Accelerometer, ambient light sensor, magnetometer, gyroscope

ipad2    Accelerometer, ambient light sensor, magnetometer, gyroscope

ipad      Accelerometer, ambient light sensor, magnetometer, gyroscope

Cameras

ipad1   None

Mini    Back 1080p HD still and video camera 5 MP, 30fps and 5× digital zoom
            Front 1.2 MP still, 720p video

ipad2   Back 720 p HD still and video camera 0.7 MP, 30fps and 5× digital zoom
            Front VGA-quality still and video camera, 0.3 MP

ipad     Back 1080p HD still and video camera 5 MP, 30fps and 5× digital zoom
            Front 1.2 MP still, 720p video

Wireless

ipad1    Wi-Fi (802.11a/b/g/n), Bluetooth 2.1+EDR
             3G cellular HSDPA, 2G cellular EDGE on 3G models

Mini     Wi-Fi (802.11a/b/g/n), Bluetooth 4.0
             3G cellular HSDPA, 2G cellular EDGE on 3G models
             3G transitional LTE on 4G model

ipad2    Wi-Fi (802.11a/b/g/n), Bluetooth 2.1+EDR
             3G cellular HSDPA, 2G cellular EDGE on 3G models

ipad      Wi-Fi (802.11a/b/g/n), Bluetooth 4.0         
             3G cellular HSDPA, 2G cellular EDGE on 3G models
             3G transitional LTE on 4G model

Geolocation

ipad1    Apple location databases
Mini     Apple location databases GPS GLONASS
ipad2    Apple location databases GPS
ipad      Apple location databases GPS GLONASS

Sim card

ipad1    Apple location databases
Mini     Nano sim
ipad2    Micro sim
ipad      Micro sim

Connectors

ipad1    30-pin
Mini     Lighting
ipad2    30-pin
ipad      Lighting

Reference 

http://en.wikipedia.org/wiki/IPad
http://store.apple.com/uk/ipad/compare