Every judgment entered in the clerk's office in a case wherein there is no order for an inquiry of damages, and every nonsuit or dismission entered therein, shall, if not previously set aside, become a final judgment on the last day of the next succeeding term of the court wherein the action is pending. If the action in which such judgment is entered be one for the recovery of money arising out of contract, and the plaintiff has filed with his declaration (which in all such cases he may do) an affidavit of himself or some other credible person stating that there is, as affiant verily believes, due and unpaid from the defendant to the plaintiff upon the demand or demands stated in the declaration, including principal and interest, after deducting all payments, credits and sets-off made by the defendant, or to which he is entitled, a sum certain to be named in the affidavit, no plea shall be filed in the case either at rules or in court, unless the defendant shall file with the plea an affidavit of himself or some other credible person that there is not, as affiant verily believes, any sum due from the defendant to the plaintiff upon the demand or demands stated in plaintiff's declaration; or stating a sum certain, less than that stated in the affidavit filed by the plaintiff, which affiant verily believes is all that is due from the defendant to the plaintiff upon the demand or demands stated in the plaintiff's declaration. If such plea and affidavit be not filed, judgment shall be entered for the plaintiff by the court for the sum stated in his affidavit, with interest thereon from the date of the affidavit until paid. If such plea and affidavit be filed by the defendant and it be admitted in such affidavit that any such sum is due from the defendant to the plaintiff, judgment may be taken by the plaintiff for the sum so admitted to be due, with interest thereon from the date of the affidavit filed by the plaintiff until paid, and the case tried as to the residue. If the plaintiff has not filed such affidavit with his declaration, and the office judgment in the case be not set aside, the judgment shall not be entered by the court until the plaintiff files such affidavit or proves his case in open court, and the judgment in either case shall be entered as heretofore provided for. If the case be one arising out of contract in which there is an order for an inquiry of damages, and the plaintiff has filed with his declaration the affidavit hereinbefore mentioned, no plea shall be filed in the case, either at rules or in court, unless the defendant shall file therewith the affidavit hereinbefore required to set aside an office judgment in which no order for an inquiry of damages had been made. When a jury is impaneled to execute an order for an inquiry of damages, their oath shall be that they will well and truly find the amount, if any, which the plaintiff is entitled to recover in the action, and a true verdict render according to the evidence. And the affidavit of the the plaintiff hereinbefore mentioned shall be legal evidence on such inquiry.