Osta software—offshore/onshore structural analysis under unix system. Structural analysis of large complex structures under static and dynamic loadings uses a large number of general purpose and special purpose algorithms in different languages, and also computer graphics (as pre- or post-processor programs) to help in the efficient and convenient interpretation of final structural designs. To enhance the portability of any sophisticated software system for large scale structural analysis, what is needed is a single program shell that would coordinate the three phases, pre-processing, analysis and post-processing, with effective user interaction. This paper highlights the utility of such a shell program (called OSTA) operating under the UNIX system. The OSTA Bourne shell interacts with a structural analysis system developed in FORTRAN 77 and a GKS-based graphic system written in ‘C’, to facilitate a systematic and efficient analysis capability in a minicomputer environment. Numerical examples are presented to demonstrate the features of OSTA for static, dynamic (deterministic/ stochastic) and reliability analyses under seismic, wave-current, wind and blast loadings.