To test basic computer skills in a job interview, you must provide a few simple tasks in the programs the job requires and ask some basic questions pertaining to them, explains CVTips.com. Most jobs require basic knowledge of Microsoft Office products and email.
If the job requires a specialized program that requires training to understand, you typically do not test a job candidate on that program.
Having the interviewee create a basic Excel spreadsheet including some basic formulas typically used in the job gives you an idea of how comfortable he is with the program. Another option is giving him specific tasks, such as data entry and alphabetizing, or having the numbers ascending or descending. Asking questions, such as what formula to use to create a specific end result on the basic functions of the program, helps as well.
If the job requires creating documents of any sort, have the candidate write a short letter to give an idea of how comfortable he is with writing and formatting. This can also give insight into how comfortable he is with working on his own and his professionalism in a written format.
With any programs the job requires, asking basic questions or creating a basic test lets you know how comfortable the applicant is.