Client Code
Client is a 3-digit number with which SAP system environment segregation is achieved. Client also represents and independent business entity in SAP system and by creating several clients, several companies can be represented in single SAP system.
When you login into an SAP system, you login to a client. You only have access to business data of the client to which you are logged in. Thus client not only segregates environment, but also segregates data. This data is known as client-specific data ( data confined to a specific client ). It is also possible to have cross-clint ( client-independent ) data ( data that is not confined to a specific client but available to all clients of the system )
SAP system uses tables to store data, and the database tables will have a client corresponding key field to make the table data client-specific. If the client corresponding key field is missing, the data of table will be a cross-client data.
The client code is perceived differently by different consultants. The Basis administrator considers client as a environment segregating parameter. A functional consultant will view client as a separate business, and an ABAP consultant will view client with respect to data segregation.