That looks like custom code to me. When working with instrument drivers, you'll typically see in the C APIs a prefix before any of the function calls that references the instrument that you are using, ie hp34401a_xxxx(), tdstks2xx_xxxx(), etc. If you use an auto generation tool to create your base code for an instrument driver, often times you have the option to define the prefix, then generate a group of generic functions, such as prefix_read(), prefix_write(), etc.
My recommendation would be for you to contact the developer who gave you that code. If they do not know what it is, please repost, and we'll see what we can find.
Logan S.
