The Add Multiple Columns message creates several columns at once. Arguments include the column name prefix, the number of columns, where to insert them (Before First, After Last, or After(col)), and the data type (Numeric, Row State, or Character(width)). An additional argument, field width, is optional for a numeric column.
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
dt << Add Multiple Columns( "beginning", 2, Before First, Row State );
// add two row state columns named "beginning <n>" before the first column
 
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
dt << Add Multiple Columns( "middle", 3, After( :height ), Numeric );
// add three numeric columns named "middle <n>" after the height column
 
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
dt << Add Multiple Columns( "end", 4, After Last, Character( 4 ) );
// add four character columns named "end <n>" after the last column

Help created on 9/19/2017