The Object Calculi proposed by Abadi and Cardelli, treat objects as primitive constructs and define operations on these objects directly. This approach used by the object calculi overcomes the problem of complex encoding of objects as functions. The object calculi do not provide the direct support for aspects and its related concepts. We propose a calculus which provides direct support for aspects and other construct of Aspect-oriented programming paradigm. Our proposed calculus is an extension to the Untyped Imperative Object Calculus which is a part of the family of object calculi. We have worked upon the syntax and operational semantics of the proposed Untyped Aspect Calculus. The paper discusses the syntax and operational semantics of the calculus. Interpreter for the calculus is also designed and implemented and the same is discussed in the paper.