The iPhone features a capacitive touchscreen that supports multi-touch sensing.
The iPhone is currently on its 5th generation. The first three generations – iPhone Original, iPhone 3G, and iPhone 3GS – have slightly lower resolution compared to the latest iPhone versions (iPhone 4 and iPhone 4S).
Although different generations might have slightly different overall dimensions, all the five versions of iPhone have 3.5 inches display – measured diagonally.
iPhone Screen Size Dimensions
Here is a comparison of their screen properties:
IPhone 4S
iPhone 4
iPhone 3GS
iPhone 3G
iPhone (Original)
Screen Size in inches3.5-inch diagonal3.5-inch diagonal3.5-inch diagonal3.5-inch diagonal3.5-inch diagonal
Screen Resolution(640) × (960) pixels at 330 ppi(640) × (960) pixels at 326 ppi(320) × (480) pixels at 163 ppi(320) × (480) pixels at 163 ppi(320) × (480) pixels at 163 ppi
Colors16.7 million colors24-bit16.7 million colors24-bit16.7 million colors24-bit262,144 colors18-bit262,144 colors18-bit
iPhone Dimensions(4.5) × (2.31) × (0.37) inches(4.5) × (2.31) × (0.37) inches(4.5) × (2.4) × (0.48) inches(4.5) × (2.4) × (0.48) inches(4.5) × (2.4) × (0.46) inches
 
One of the highlights of the first two generations when it comes to the property of their display is their scratch resistant screen. This was later improved in the next versions by making it fingerprint-resistant and adding oleophobic coating.