Under section 4 (2) (a) of the Companies Act, a company limited by shares means that a member thereof can only be called upon to contribute to the assets of the company the amount if any outstanding on his shares beyond which he is not liable.
Under section 4 (2) (b) of the Companies Act, company limited by guarantee means that a member can only be called upon to contribute to the assets of the company the amount he undertook to contribute, if the company was wound up during his membership or within 1 year of cessation of membership, beyond which he is not liable.