In applied problems related to the study of non-stationary thermal processes, often arise a situation where it is impossible to carry out direct measurements of thedesired physical quantity and its characteristics are restored on the results of indirect measurements. In this case the only way to finding the required values is associated with the solution of the inverse heat conduction problem with the initial data, known only to the part of the boundary. Such problems appear not only in the study of thermal processes, but also in the study of diffusion processes and studying the properties of materials related to the thermal characteristics. This article is devoted to the approximate solution of the Volterra equations of the first kind received as a result of the integral Laplace transform to solve the heat equation. The work consists of an introduction and three sections. In the first two sections the specificity of Volterra kernels of the corresponding integral equations and peculiarity of computing kernels over the machine arithmetic operations on real numbers with floating point are considered. In tests typically systematic accumulation of errors are illustrated. The third section presents the results of numerical algorithms based on product integration method and middle rectangles quadrature. The conditions under which used algorithms are stable and converge to the exact solution in the case of fixed digit grid in the computer representation of numbers are allocated. Series of test calculations are carried out in order to test the efficacy of difference methods.

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