Example apparatus and methods concern controlling a computer to prevent read while writing occurrences in direct output. One example method includes identifying a non-conformance between a block of data intended to be output using direct output and a desired direct output block. Conventionally, the non-conformance would cause the computer to perform a read operation to provide additional data suitable for conforming the block of data to the desired direct output block. Once the method has identified the non-conformance, the method may prevent the computer from performing the read operation. The method may also control the computer to perform an additional output operation to make the block of data appear to conform to the desired direct output block. The additional output operation will be performed without performing a read operation. In one embodiment, the method is performed in the kernel of an operating system running on the computer.