The doctrines of res sub judice and res judicata are fundamental principles under the Code of Civil Procedure, 1908, aimed at ensuring judicial efficiency and preventing multiplicity of litigation. While res sub judice (Section 10 CPC) restricts courts from proceeding with a trial when a similar matter is already pending before a competent court, res judicata (Section 11 CPC) bars the re-litigation of issues that have already been finally decided. Together, these doctrines uphold the finality of judgments, avoid conflicting decisions, and promote certainty in the administration of justice.