SAP is the fourth largest software company in the world. It ranks after Microsoft, IBM and Oracle in terms of market capitalization. SAP is the largest Enterprise Resource Planning (ERP) solution software provider.SAP's products focus on ERP, which it helped to pioneer. The company's main product is SAP R/3;the "R" stands for real time data processing and the number 3 relates to a three-tier application architecture: database, application server and client SAPgui.Other major product offerings include Advanced Planner and Optimizer (APO),Business Information Warehouse(BW), Customer Relationship Management(CRM),Supplier Relationship Management(SRM), Human Resource Management Systems(HRMS),Product Lifecycle Management(PLM), Exchange Infrastructure(XI) and Knowledge Warehouse(KW).