Constructions of algebraic-geometry codes

Based on curves over finite fields with many rational points, we present tw o constructions of linear codes from local expansions of functions at a fix ed rational point. It turns out that codes from our constructions have the same bound on their parameters as Goppa's geometry codes. Furthermore, we p rove that our second construction is equivalent to Goppa's construction, Fi nally, an additional construction of linear codes from maximal curves shows that these codes have better parameters than Goppa's geometry codes from m aximal curves for a certain interval of parameters.