Readers of technical and scientific writing, whatever their level of expertise, read a document for three general purposes:
Readers at all levels of expertise read technical documents to acquire information. Experts read current documents in their own fields to maintain their level of expertise and read documents in related fields to increase the breadth of their knowledge. Furthermore, experts or technicians in one field are often novices in another field and read documents to acquire a basic understanding. Sometimes technicians read documents to acquire a basic understanding of general concepts and processes that will help them perform their tasks and diagnose and solve problems they may encounter. Managers read to acquire both the general and the specific information necessary for them to supervise their staffs effectively and to function well in their organizations. Laypersons read scientific and technical documents to acquire general knowledge about a subject or as novices attempting to become experts.
Readers at all levels of expertise read documents to make decisions. An expert may read a technical study to decide whether or not to conduct a specific experiment or to use a new design element. A manager may need to make or approve a decision. Technicians use documents to decide on the selection of specific hardware and software and to determine the best procedure for performing a task. Laypersons may read documents to help select a particular product or investment.
All readers, whatever their level of expertise, sometimes read instructions to help them perform various tasks. A manager may read a document to learn how to use new budgeting software. An expert may read a document to learn how to use a new device. Instructions are an essential part of a technician's role in performing tasks and making things work. Finally, as laypersons, all of us use instructions to perform everyday tasks, from using an Automated Teller Machine to filling out our income tax forms.