-377(7) to what extent and in what circumstances a party calling a witness shall be permitted, and a party not calling him shall be forbidden, to put to the witness questions suggesting the desired answers; (8) to what extent and in what circumstances a party crossexamining a witness may be forbidden to examine him concerning material matter not inquired about on a previous examination by the judge or by an adverse party; (9) whether or upon what condition a party may put questions or use any writing, object or other means for the purpose of reviving the memory of a witness; (10) whether a witness in communicating admissible evidence may use as a substitute for oral testimony or in addition to it a writing, model, device or any other understandable means of communication, and whether a means so used may be admitted in evidence; (11) whether counsel may use a writing, model or other device as a means of conveying a reasonably accurate understanding of his interpretation of admitted evidence; (12) whether or upon what condition an adverse party shall upon demand made at the trial submit for inspection to the demanding party a writing or object found by the judge to be in the control of the adverse party and readily accessible and to constitute or contain evidence admissible against the adverse party; and (13) whether or not an exhibit which has been received in evidence shall be available to the jury after its retirement to deliberate upon the verdict. § 2682. Presence of parties Upon a trial, a witness may be heard only in the presence and subject to the examination of all the parties, if they choose to attend and examine. § 2683. Exclusion of witnesses (a) In his discretion, on his own motion or on the request of a party, the judge may exclude from the courtroom any witness not at the time under examination, so that he may not hear the testimony of other witnesses. A party to the action or proceeding may not be so excluded; and if a corporation is a party, it is entitled to the presence of one of its officers, to be designated by its attorney. (b) In a criminal action, the judge may also cause the witnesses to be kept separate and to be prevented from conversing with each other until they are examined. § 2684. Postponement for absence of evidence A motion to postpone a trial on the ground of the absence of evidence may be made only upon affidavit snowing the materiality of the evidence expected to be obtained, and that due diligence has been used toM-ocureit. The court may require the moving party, where application is made on account of the absence of a material witness, to state upon affidavit the evidence which he expects to obtain. If the adverse party thereupon admits that the evidence would be given, and that it be considered as actually given on the trial, or offered and overruled as improper, the trial may not be postponed.