iPad display Resolutions

iPad 3 - retina display with a resolution of 2048 x 1536 
iPad 2 - 1024-by-768-pixel resolution at 132 pixels per inch (ppi)
iPad 1 - 1024 x 768

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Display 9.7-inch
LED-backlit IPS LCD 9.7-inch
LED-backlit IPS LCD
Resolution 1024 x 768 1024 x 768
Processor 1GHz Apple A4 1GHz dual-core Apple A5
Graphics PowerVR SGX 535 ?
Memory 256MB RAM ?
Storage 16GB / 32GB / 64GB 16GB / 32GB / 64GB
Front camera none VGA
Rear camera none 720p
Cellular radio EDGE plus triband HSPA EDGE plus quadband HSPA or
CDMA / EV-DO Rev. A
WiFi 802.11a/b/g/n 802.11a/b/g/n
Bluetooth 2.1 + EDR 2.1 + EDR
Accelerometer 3-axis 3-axis
Gyroscope No 3-axis
Thickness 13.4mm 8.8mm
Weight 680g (WiFi),
730g (WiFi + 3G) 601g (WiFi),
607g (Verizon),
613g (AT&T)

Introspection and id

Useful to programmatically make use and discover something about an 'id'.

- (BOOL)isKindOfClass:(Class)aClass
- (BOOL)isMemberOfClass:(Class)aClass
- (BOOL)respondsToSelector:(SEL)aSelector
- (BOOL)conformsToProtocol:(Protocol *)aProtocol

id is pointer to any kind of object

id is pointer to any kind of object