The Argument is a value that is passed to a function, subroutine, or command when it is called or executed. It provides the specific information that the function needs to perform its task. In programming, functions are often defined with "parameters," which act as placeholders for the data they will receive. When the function is actually used, the specific values provided are the "arguments."
For example, in a command to control a programmable power supply, such as SOUR:VOLT 12.5, the command is SOUR:VOLT and the argument is 12.5. This argument tells the power supply the specific voltage level to set. Without the argument, the command would be incomplete. Similarly, in a programming language using a driver API, a function call like PowerSupply.SetOutput(channel=1, voltage=12.5, current=2.0) uses several arguments (1, 12.5, 2.0) to specify the channel number, the desired voltage, and the current limit.
The arguments are the concrete data that bring a general command or function to life, enabling precise and dynamic control of the instrument. The type and range of valid arguments are defined by the command language specification (e.g., SCPI) or the API documentation. Sending an invalid argument, such as a negative voltage to a power supply that only supports positive output, will typically result in an error that must be handled by the control program.