A contract is an agreement to do or not to do a certain thing.
§ 28-2-101, MCA
En. Sec. 2090, Civ. C. 1895; re-en. Sec. 4965, Rev. C. 1907; re-en. Sec. 7467, R.C.M. 1921; Cal. Civ. C. Sec. 1549; Field Civ. C. Sec. 744; re-en. Sec. 7467, R.C.M. 1935; R.C.M. 1947, 13-101.