[1, 2] Plaintiff’s appeal presents the question of whether judgment notwithstanding the verdict was properly entered against him. Judgment notwithstanding the verdict should be granted only when the evidence is insufficient as a matter of law to support the verdict. Where the evidence admitted at trial, taken in the light most favorable to the non-moving party with all reasonable inferences drawn in his favor, is sufficient to support the verdict, it should not be set aside. Summey v. Cauthen, 283 *508N.C. 640, 197 S.E. 2d 549 (1973); Brokers, Inc. v. High Point City Board of Ed., 33 N.C. App. 24, 234 S.E. 2d 56 (1977), cert. den., 293 N.C. 159, 236 S.E. 2d 702. The ground for granting judgment notwithstanding the verdict was, that the jury had before it parol evidence that added to the written agreement and thus violated the parol evidence rule. The parol evidence was admitted over defendant’s objection and tended to show that the employment contract was for a definite term of three years. The general rule is that all evidence admitted, whether it be competent or not, must be given full probative force in determining the correctness of a directed verdict or of a judgment notwithstanding the verdict. Bishop v. Roanoke Chowan Hospital, Inc., 31 N.C. App. 383, 229 S.E. 2d 313 (1976); see Dixon v. Edwards, 265 N.C. 470, 144 S.E. 2d 408 (1965).
The trial judge, however, stated that the parol evidence rule was “not really a rule of evidence, but of substantive law” and that plaintiff’s parol evidence, as a matter of law, could not be used to prove that there was a definite term of employment. We note, however, that the Supreme Court of North Carolina has elected to treat the rule as one of evidence in the sense that evidence admitted in violation of the rule, if admitted without objection, may be considered and allowed to prove facts that would otherwise not be provable at all. Bishop v. DuBose, 252 N.C. 158, 113 S.E. 2d 309 (1960). In Products Corporation v. Chestnutt, 252 N.C. 269, 275, 113 S.E. 2d 587, 593 (1960), the Court noted that, while there was much authority for the proposition that the rule was not one of evidence but of substantive law, “[t]here are North Carolina decisions which treat it solely as a rule of evidence.” The Court then declined to explore the question further, and we need not do so on this appeal. Our conclusion is that parol evidence was properly admitted to prove a definite three-year term of employment.
When a contract is reduced to writing, parol evidence cannot vary its terms. When a contract is partially parol and partially written, parol evidence may prove the parol terms. Hoots v. Calaway, 282 N.C. 477, 193 S.E. 2d 709 (1973); Williams & Assoc. v. Ramsey Products Corp., 19 N.C. App. 1, 198 S.E. 2d 67, 69 A.L.R. 3d 1348 (1973), cert. den., 284 N.C. 125, 199 S.E. 2d 664.
[3] “A contract for service must be certain and definite as to the nature and extent of the service to be performed, the place *509where, and the person to whom it is to be rendered, and the compensation to be paid, or it will not be enforced.” Croom v. Goldsboro Lumber Co., 182 N.C. 217, 220, 108 S.E. 735, 737 (1921); McMichael v. Borough Motors, Inc., 14 N.C. App. 441, 444, 188 S.E. 2d 721, 722 (1972). The paperwriting which the court apparently characterized as a complete contract purports on its face to be an agreement between plaintiff and Kyle Stephenson individually and calls for the performance of services for K. H. Stephenson Supply Co. The parties both offered evidence which tended to show that plaintiff’s employment was terminated due to suspected irregularities in work done for S & H Floral Garden. The paperwriting does not mention S & H, yet the testimony that plaintiff was expected to perform accounting duties for the Floral Garden was undisputed. Indeed, Kyle Stephenson, the president of the defendant corporation, testified that the work for the other business “was all figured in the original contract.” This alone is enough to show that the paperwriting did not constitute the entire agreement between the parties. We also point out that the written agreement does not set a date for plaintiff to begin employment even though there is undisputed evidence that the parties agreed that he would begin work on 15 April 1973. Indeed, about the only element of an enforceable employment contract which is definite on the face of the paperwriting is the amount of compensation to be paid. Since the parties agreed there were some other terms, it cannot be said as a matter of law that the paperwriting represented the whole contract between the parties. Evidence that the parties agreed that plaintiff would be employed by K. H. Stephenson Supply Company from 15 April 1973 to 31 December 1976 neither contradicts nor changes that which is written. The only pertinent term from the written agreement provides that “[s]alary increments are to be 5%, 772%, and 10% for the three year period beginning January 1, 1974.” As defendant points out, this provision alone is insufficient to show that the contract was for a definite period. Freeman v. Hardee’s Food Systems, Inc., 3 N.C. App. 435, 165 S.E. 2d 39 (1969). Nevertheless, it is not contradicted or changed by an additional contract provision that the term of the employment be from 15 April 1973 to 31 December 1976. Thus the parol evidence as it tended to prove that the contract was for a definite term was properly admitted. When the parol evidence is given its full probative force, it is sufficient to support the verdict. The evidence does not, *510when considered in the light most favorable to plaintiff, require a finding that there was just cause for defendant’s discharge of plaintiff. The judgment notwithstanding the verdict should be reversed and judgment should be entered on the verdict. Snellings v. Roberts, 12 N.C. App. 476, 183 S.E. 2d 872 (1971), cert. den., 279 N.C. 727, 184 S.E. 2d 886; Mus grave v. Savings & Loan Assoc., 8 N.C. App. 385, 174 S.E. 2d 820 (1970).
[4] Although G.S. 1A-1, Rule 50, provides that “[a] motion for a new trial may be joined with this motion [for judgment notwithstanding the verdict], or a new trial may be prayed for in the alternative,” defendant did not at any time move for a new trial. By his failure to seek a conditional ruling on this question, he has also failed to preserve for our review any errors which may have entitled him to a new trial. See Hoots v. Calaway, supra; see also 2 McIntosh, North Carolina Practice & Procedure, § 1488.45 (Phillips Supp. 1970). A party gaining judgment notwithstanding the verdict should also ask for a ruling pursuant to G.S. 1A-1, Rule 50(c)(1), on the motion for a new trial if he wishes to allege any error in the trial or to preserve any question other than the sufficiency of the evidence for appellate review.
Reversed and remanded for entry of judgment on the verdict.
Judges PARKER and WEBB concur.