The paper considers the language constructs that give a real meaning to the structures makes applied methodology itself to be easy to understand and the program becomes close to the way of thinking about the problem on hand. The concept of streams is emphasized as a means for reaching the high quality of programs. Also, there are given an informal and formal definitions of streams. Formal definition of the stream consists of sixteen axioms based on the formulas of algorithmic logic and abstract functions . The meaning and the purpose of these axioms is that every implementation that satisfies them is a stream.