---
title: blockStart
framework: kernel
role: symbol
role_heading: Instance Property
path: kernel/ioblockstoragedeviceextent/1568446-blockstart
---

# blockStart

The starting block number of the operation.

## Declaration

```occ
UInt64 blockStart;
```

## See Also

### Fields

- [blockCount](kernel/ioblockstoragedeviceextent/1568453-blockcount.md)