Fields are used to specify the format of a machine instruction.
The dialog for creating and editing fields (see Figure 23) has a table in which you can inspect and edit the properties of existing fields and in which you can add new fields or delete fields.
Figure 23. The dialog for editing the fields of machine instructions.
To delete a field, select it in the table and then click the "Delete" button. To create a new field, click in the "New" button, at which point a new field will be added to the table. To duplicate an field, select the field in the table and click the "Duplicate" button. To edit a cell, first click or double-click on it to select it. Some cells are edited by typing new text in them, some cells are edited by selecting items from popup menus, and some cells are edited just by clicking in the check box in the cell. If you try to enter an illegal value in a cell, either the cell will become outlined in red (for example, if you type a non-numeric value in a cell that can only contain a numeric value) or an error message will appear when you try to save the changes you made.
The columns in the table can be reordered by dragging the column headers left or right to a new position. The column widths can also be adjusted by dragging the line dividing the column headers. The rows can be resorted by column by clicking in any column header.
To create a set of values for a field, first select the row containing the field and then click on the "Values..." button. A dialog box (not shown here) will appear that is similar to the EQUs dialog in which you can create a set of names and associated values.