---
title: kIOPropertyCylinderCountKey
framework: driverkit
role: symbol
role_heading: Macro
path: driverkit/kiopropertycylindercountkey
---

# kIOPropertyCylinderCountKey

## Declaration

```occ
#define kIOPropertyCylinderCountKey
```

## Discussion

Discussion This key is used to define the number of heads for a particular medium. Requirement: Mandatory element of the Rigid Disk Geometry dictionary. Example:     <dict>    <key>Device Characteristics</key>    <dict>    	<key>Vendor Name</key>    	<string>Apple</string>    	<key>Product Name</key>    	<string>iPod</string>    	<key>Product Revision Level</key>    	<string>1.0</string>    	<key>Rigid Disk Geometry</key>    	<dict>    		<key>Sector Count per Track</key>    		<integer>12345</integer>    		<key>Head Count</key>    		<integer>12</integer>    		<key>Cylinder Count</key>    		<integer>12345</integer>    		<key>Bytes per Physical Sector</key>    		<integer>512</integer>    	</dict>    </dict> </dict>

## See Also

### Macros

- [ALWAYS](driverkit/always.md)
- [APPLE_KEXT_OVERRIDE](driverkit/apple_kext_override.md)
- [DEFN](driverkit/defn.md)
- [DRIVERKIT_CONSUMED](driverkit/driverkit_consumed.md)
- [DRIVERKIT_CONSUMES_THIS](driverkit/driverkit_consumes_this.md)
- [DRIVERKIT_FRAMEWORK_INCLUDE](driverkit/driverkit_framework_include.md)
- [DRIVERKIT_IOLIB_H](driverkit/driverkit_iolib_h.md)
- [DRIVERKIT_OSCOLLECTIONS_H](driverkit/driverkit_oscollections_h.md)
- [DRIVERKIT_RETURNS_NOT_RETAINED](driverkit/driverkit_returns_not_retained.md)
- [DRIVERKIT_RETURNS_RETAINED](driverkit/driverkit_returns_retained.md)
- [DRIVERKIT_RETURNS_RETAINED_ON_NONZERO](driverkit/driverkit_returns_retained_on_nonzero.md)
- [DRIVERKIT_RETURNS_RETAINED_ON_ZERO](driverkit/driverkit_returns_retained_on_zero.md)
- [ERR_SUCCESS](driverkit/err_success.md)
- [EXTENDS](driverkit/extends.md)
- [HIDDEN](driverkit/hidden.md)