Learning programming is a complex process that requires understanding abstract concepts and solving problems efficiently. To support and motivate students, educators can use technology-enhanced learning (TEL) in the form of visual tools for knowledge mapping. Mytelemap, a prototype tool, uses TEL to organize and visualize information, enhancing students' understanding and problem-solving abilities. An experiment was conducted to explore students' use of knowledge mapping in object-oriented programming (OOP) classes, investigating the relationships between subject matter and competence mappings, the quality of students' maps, their learning achievement, and their perceptions of mapping activities. Undertaking knowledge mapping improved students' attitudes towards learning and was found to be a strong predictor of learning achievement. The quality of mapping as such was not related to learning achievement, but it helped students identify the knowledge they needed.