# Base Counter Types

Some formulas require both a counter property and base property. The base value is the denominator in the formula for the counter type. In raw data Performance Counter Classes derived from **Win32_PerfRawData**, the base property must immediately follow the counter property. The base property must have the same name as the preceding counter, with **_Base** appended.

For example, the **AvgDiskBytesPerRead** property in **Win32_PerfRawData_PerfDisk_LogicalDisk** contains the raw value, in bytes, transferred from the disk during read operations. It has a base property, **AvgDiskBytesPerRead_Base**, which represents the accumulated number of operations. When WMI applies the formula for the specified counter type, **PERF_AVERAGE_BASE**, **AvgDiskBytesPerRead** is divided by **AvgDiskBytesPerRead_Base** to produce the average value. This value appears in System Monitor and is stored in the corresponding **Win32_PerfFormattedData_PerfDisk_LogicalDisk** property. Base properties are only used in raw data classes.

In classes derived from **Win32_PerfFormattedData**, the **Counter** qualifier specifies the numerator property in the raw class and the **Base** qualifier specifies the base denominator property.

The following table lists the **CounterType** constant values.

CounterType Constant | Description |
---|---|

PERF_AVERAGE_BASEDecimal 1073939458 |
Base value used to calculate the PERF_AVERAGE_TIMER and PERF_AVERAGE_BULK counter types. |

PERF_COUNTER_MULTI_BASEDecimal 1107494144 |
Base value used to calculate the PERF_COUNTER_MULTI_TIMER, PERF_COUNTER_MULTI_TIMER_INV, PERF_100NSEC_MULTI_TIMER, and PERF_100NSEC_MULTI_TIMER_INV counter types. |

PERF_LARGE_RAW_BASEDecimal 1073939712 |
Base value found in the calculation of PERF_RAW_FRACTION, 64 bits. |

PERF_RAW_BASEDecimal 1073939459 |
Base value used to calculate the PERF_RAW_FRACTION counter type. |

PERF_SAMPLE_BASEDecimal 1073939457 |
Base value used to calculate the PERF_SAMPLE_COUNTER and PERF_SAMPLE_FRACTION counter types. |