(a) It shall be the duty of each officer to investigate all cases referred to him or her by the court and to make findings and report thereon in writing to the court with a recommendation. The superior court may require, before imposition of sentence, a presentence investigation and written report in each felony case in which the defendant has entered a plea of guilty or nolo contendere or has been convicted.
(b) An officer shall cause to be delivered to each person placed on probation under his or her supervision a copy of the terms of probation and any change or modification thereof and shall cause the person to be instructed regarding the same. An officer shall keep informed concerning the conduct, habits, associates, employment, recreation, and whereabouts of the probationer or parolee by visits, by requiring reports, or in other ways. An officer shall use all practicable and proper methods to aid and encourage persons on probation or parole and to bring about improvements in their conduct and condition.