Which of the following is a typical example of a system requirement for input?

System requirements for input specifically detail how data is to be entered into a system. In this context, the statement about student grades needing to be entered on machine-readable forms clearly defines a requirement related to input methods. It specifies not only what data (student grades) is being collected but also how it should be formatted (machine-readable forms), thus ensuring that the system can effectively process and utilize the input.

The other options reflect requirements that pertain to different aspects of the system. Storing data in a database relates more to data storage requirements rather than input procedures. Generating reports weekly involves output requirements, focusing on how data is displayed or utilized once it has been processed. Adjusting user permissions pertains to access control and security aspects of the system, not the method of data input. Therefore, the focus on how grades are to be inputted makes the chosen option the most fitting example of a system requirement for input.