Test-driven development (TDD) is a software development practice, where test cases are incrementally written before implementing the production code. This paper presents the results of a multi-case study investigating the effectiveness of TDD within an industrial environment. Three comparable medium-sized projects were observed during their development cycle. Two projects were driven without TDD practice, while the third one introduced TDD into the development process. The effectiveness of TDD was expressed in terms of external code quality, productivity, and maintainability. Our results indicate that the TDD developers produced higher quality code that is easier to maintain, although we did observe a reduction in productivity.

This paper considers the problem of setting small and accurate delay of those analog quadrature signals generated in the sin/cos encoders within the range of ±10°. Such precision is needed for the efficient phase shift compensation. A typical analog delay circuit is comprised of a summing amplifier and digitally controlled variable resistor used to set a delay of the cos signal. The main disadvantage of this delay circuit is poor linearity. We propose a new circuit based on a voltage divider with about three times better linearity and a completely symmetrical range. The effects of the component tolerances and signals' irregularities on the accuracy of the delay are explored. The detailed theoretical worst case analysis and simulation shows that for the integrated version with the 128-tap digital potentiometer ( R/R = 1 LSB = 0.8%), the tolerances contribute 0.34°to the total error and typical signal irregularities of ∼0.40°. The measurement of the prototype circuit shows that with the discrete elements it is possible to obtain a total error of below 0.2°within the range from 0°to 5°, if the signals are of good quality.Index Terms-Analog quadrature signals, delay circuit, error analysis, phase delay, quadrature encoder signals.

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Absfract-In this paper, basic principles and comparison of software (SW) development models are presented. First part is the presentation of development models as they are thought and studied by software engineering teachers and students. In its second part, the paper introduces a practical approach to implement one of the SW development models. Finally, the problem of determining the most suitable SW development model in the case of developing PC applications in the field of CT (ComputerTelephony) systems is presented.

Abstract-This paper presents a systematic approach for designing a C++ app for demonstrating sorting algorithms on smartphones and tablets. It is part of an on-going project on the usages of new technologies in education. The general properties of mobile platforms are discussed together with details specific to demonstrating sorting algorithms. The implementation of Insertion Sort is given as an example. The obtained results (e.g. design rules and algorithms) have been tested within a prototype application.