How can System Architecture be categoriesed in Software Architecture?

System requirements can be categorized as:

1. Functional requirements:State what the system must do, how it must behave or react to run-time stimuli.  
2. Quality attribute requirements:Annotate (qualify) functional requirement, e.g. how fast the function must be performed, how resilient it must be to erroneous input, how easy the function is to learn, etc. 
3. Constraints:A design decision with zero degrees of freedom. A design decision that has already been made for you.