The one originally obligated to the creditor for his own debt is called the principal, or the principal debtor, and since the principal debtor is so closely connected with the surety's contract with the creditor, which is to answer for the principal's default, the principal must not be lost sight of, as his relation and his contract with the creditor is the basis of the surety's contract. The principal debtor is the one whose debt or default the surety agrees to answer for, or, in other words, his possible unpaid debt or default is the basis of the transaction between the creditor and the surety. The principal may be one in charge of certain sums of money, or one holding an office, carrying with it the duty to keep safe the funds intrusted to him, and one who personally becomes security for any default of the principal in the conduct of that office, and would be in default on his agreement when the principal defaults in his duties for which the surety has become the security. The principal's obligation which the surety may secure may be of a wide range. His failure to pay any debt, or the possible breach in a promise to perform some obligation, or a possible miscarriage of his duties or obligations, owing to another, for all or any of these things, the surety may by express contract, make himself liable, the obligation of the principal continuing also.