Data Communication is the third chapter that has been added in the syllabus of Computer Science ICS-I (Intermediate Part-1). Today, Computer Science is widely used in almost 99% of the organizations and its importance cannot be neglected today. After the introduction of Computers, the business world changed forever. Almost 99% of the businesses today use Information Technology to ensure their departments run smoothly. Information Technology is widely used today in the core departments of all the organizations like Human Resources (HR) / Personnel, Finance, Budget and Security. In this chapter the students will learn about the Introduction of data communication, elements, modes, Types of data, Encoding different types of data, Transmission media and speed, methods, Modem, modulation and demodulation.