These variables control parameters and modes related to simulation. Most of these variables can be set indirectly from the Simulation Options tool from the Sim Opts button in the Tools menu of the Tool Control window, which is equivalent to using the set command to set the variable in the WRspice shell.
Most of these variables are referred to as ``options'' in historic SPICE vernacular as they are commonly given in a .options line in SPICE input. In versions of SPICE that are batch-mode only, this is the only way to set these parameters. In WRspice, there is little difference between shell variables and options, however there are subtleties, particularly with respect to resolving conflicts if one of these parameters is set both as a shell variable and in a .options line in the current circuit. These issues are discussed in the section desctibing the options, 2.4.4.1.