The book deals with computational methods most often used in the practice of applied and scientific and technical calculations. Methods of solving problems of linear algebra , Nonlinear Equations , Problems of own significance , Methods of Theory of Approximation of Functions , Numerical Differentiation and Integration, search for extremities of functions, solution of ordinary differential equations , Numerical solution of integral equations , Linear and nonlinear problems of the least squares method , method of conjugated gradients. Considerable attention is paid to the features of the implementation of computational algorithms on the computer and the assessment of the reliability of the results There are a large number of examples and geometric illustrations. Information is given on the IEEE standard, on singular matrix decomposition and its application for solving overdetermined systems, on two-layer iterative methods, on Gauss-Cronrod quadrature formulas, on Runge-Kutta-Felberg methods . The training manual is intended for students of all fields of study studying at classical and technical universities and studying computational methods, it will be useful for graduate students, engineers and researchers applying computational methods in their research.