The iPhone keypad has a lot of the same keys, buttons and symbols you can find on your desktop or laptop keyboard. Because of its small size, all of the keys are not visible on the iPhone's main alphabetic keypad. You can only access numbers and symbols on another keypad screen. The iPhone keypad will become more familiar once you know where to look for all of the buttons.
Bring up your keypad.
Tap the "?123" button in the lower-left corner of the keyboard. A new keypad with numbers and symbols will appear.
Tap the "#+=" button above the "ABC" button toward the lower left of the keyboard. Another keypad with more symbols and punctuation marks will load.
Tap the "\" button to enter a backslash into the type field.