Like any function or procedure in any other programming language, stored procedures communicate with applications or clients through parameters. The maximum number of parameters in a stored procedure is 2,100 (this was significantly increased from SQL Server 7, which had a maximum of 1,024 parameters per stored procedure).
Be aware that Books Online incorrectly states in the "Maximum Capacity Specifications" section that the maximum number of parameters in a stored procedure is 1,024.
When you develop stored procedures, to be able to access the value of a parameter inside the stored procedure's body, you just have to specify the parameter's name (including the @ character).
Once created, information about stored procedures' ...