OC Basic Data type

Boolean data type bool (YES (1)/no (0))

NSLog () is equivalent to printf ()
NS: Use prefixes to avoid name collisions when derived from toolkits also known as NeXTSTEP.
NSLog (@ "hello,objective-c!");

Basically all variables start with @.
The string begins with @.
The @ symbol means that the string within the quotation marks should be treated as a nsstring element of the cocoa
The @ symbol in OC is considered an extension of the C language.

for (int i=0;i<5;i++) {
NSLog (@ "%d\n", I);
}

The NSLog () command outputs a word through the%s format, and%s outputs an array of C strings instead of an array of @ "NSString" objects.
The%lu format specifier takes the integer value of the strlen () function that evaluates the length of the string

OC Basic Data type