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# Base Utilities

## Overview

Core Foundation defines a number of miscellaneous symbols that are either used by many different opaque types, such as [`CFIndex`](/documentation/CoreFoundation/CFIndex), or apply to Core Foundation as a whole, such as [`kCFCoreFoundationVersionNumber`](/documentation/CoreFoundation/kCFCoreFoundationVersionNumber). These symbols are collected together and documented here.

## Topics

### Core Foundation Base Utilities Miscellaneous Functions

[`CFRangeMake`](/documentation/CoreFoundation/CFRangeMake(_:_:))

Declares and initializes a `CFRange` structure.

### Callbacks

[`CFComparatorFunction`](/documentation/CoreFoundation/CFComparatorFunction)

Callback function that compares two values. You provide a pointer to this callback in certain Core Foundation sorting functions.

### Data Types

[`CFIndex`](/documentation/CoreFoundation/CFIndex)

Priority values used for kAXPriorityKey

[`CFOptionFlags`](/documentation/CoreFoundation/CFOptionFlags)

A bitfield used for passing special allocation and other requests into Core Foundation functions.

[`CFRange`](/documentation/CoreFoundation/CFRange)

A structure representing a range of sequential items in a container, such as characters in a buffer or elements in a collection.

### Constants

[`CFComparisonResult`](/documentation/CoreFoundation/CFComparisonResult)

Constants returned by comparison functions, indicating whether a value is equal to, less than, or greater than another value.

[Value Not Found](/documentation/CoreFoundation/value-not-found)

Special value returned when a Core Foundation function cannot locate a requested value.

[Current Framework Version Number](/documentation/CoreFoundation/current-framework-version-number)

Current version number of the Core Foundation framework.

[Framework Version Numbers](/documentation/CoreFoundation/framework-version-numbers)

Version numbers of the Core Foundation framework.

## See Also

  [Core Foundation Design Concepts](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFDesignConcepts/CFDesignConcepts.html#//apple_ref/doc/uid/10000122i)


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