Definitions and Techniques. Repairing errors, improving the design, implementing extensions, interfaces with other systems, adapting programs to different hardware, software, systems with the ability to use the results in the field of telecommunications; the legality of the software, the withdrawal of software, maintenance of everyday functions, maintenance and software modifications, perfection of existing functions, preventing degradation of software performance to unacceptable levels. The bulk of maintenance costs. Software development. Categories of maintenance (corrective maintenance, adaptive maintenance, perfective maintenance, preventive maintenance). Reengineering. Reverse engineering. Technical issues (limited understanding, testing, impact analysis, determining the scope of the changes for better planning and implementation, development of accurate assessments of resources; analysis of cost/benefits of the required changes, communication with others in connection with the complexity of the change; sustainability). Control issues (conformance to organizational structures, personnel, process, and organizational aspects of maintenance, outsourcing). Assessment of maintenance price (price estimate, parametric models, experience). Measurements in software maintenance (specific measures, the possibility of analysis, variability, stability, testability). The maintenance process (implementation of process, problem and analysis of modification, modification implementation, migration, withdrawal of software). Maintenance activities (unique activities, transition, modification request acceptance/rejection, modification request and report of help desk, impact analysis, software support, contracting service level, supporting activities, the activity of maintenance planning, business planning (organizational level), maintenance planning (transition level), planning versions (software level), the demand of planning individual software changes (demanding level), a conceptual document of maintenance, the boundaries of software maintenance, adaptation of the software maintenance process.