NSLog, and its corresponding C function printf(), use escape sequences to print certain characters that are “invisible.” For iOS, include:

There are others, such as \a
for Alert, but they are rarely used, and don’t make an effect.
Format specifiers, however, are the percent character, followed by a letter, such as %d
or %f
that tell NSLog or printf() to print the value or result of a variable, value, and/or expression.
Click here for a list of C format specifiers.
Just think of them as types of placeholders, each designed to represent a different value.
This post is part of the Learn Objective-C in 24 Days course.
Author: Feifan Zhou