Track and vertex reconstruction in the ATLAS inner detector

This thesis describes the construction and commissioning of ATLAS SCT endcap A. The performance of the detector modules and the optical readout system was measured during various construction stages and the results are presented in this document. This thesis also describes a tool for vertex fitting with kinematic constraints in ATLAS. A study was made for solving systematic misalignments using a mass constraint in events of J/psi decaying to two muons.