The 'HISTSIZE' mnemonic sets the maximum capacity of the command history
list in a BBj SysConsole or TermConsole. By default, the command history
stores the 30 most recently issued commands given at the command prompt
in immediate mode. The number given as a parameter with this mnemonic
increases or decreases the number of stored commands.
This mnemonic has no effect whatsoever on an executing program or on a SysWindow, since the console command prompt ('>') never appears there.