System software:GEM

GEM

Figure 5.3 shows a GEM display, with a window showing the contents of the root directory of the disk in Drive A. Note the slide bar at the right of the window, which you can use to scroll through the contents of the directory. The procedure is to 'point' to it with the mouse (i.e. move the arrow on the screen to it), hold down the mouse button, and 'drag' it to a new position.

Quite a number of applications programs are able to run within the GEM or Windows environments. This means that they do not take over the entire screen but instead carry out their tasks within the confines of a window, and are therefore able to take advantage of facilities such as scroll bars and pull-down menus.

The opening display that appears on the screen when you run GEM (or the equivalent product on the Apple Mac, or indeed Windows) is called the Desktop. In the Mac and GEM environments it contains:

• Icons representing the disk drives available on the system, e.g. Drive A and Drive C.

• An icon representing a trash-can, used for deleting files.

• Functions listed across the top, which, when selected, reveal pull-down menus.

From the Desktop you can perform one or more of the operations listed below. In these operations much use is made of windows. You can open several windows on the screen at the same time, each one showing different infor­mation. The one in which you are currently working is called the active window, and it may partly obscure other windows. You can open windows, close windows, expand or contract

windows, and move windows around the screen. How you do this is explained below.

(Note that the latest version of GEM Desktop on the PC has had a number of these features removed. If you use GEM on a PC, it is worth getting hold of the pre-October 1986 version of GEM Desktop. GEM on the Atari ST and the Apricot F2 works as described below, as does the pre- 86 version on the PC and the virtually identical system on the Apple Mac.)

1 Open a drawer. One operation is opening a 'drawer', i.e. displaying a catalogue of the contents of one of the drives. You do this by using the mouse to move the pointer to the drive icon and double-clicking. A window appears on the screen, displaying the catalogue in icon form, as shown in Figure 5.3. Each file in the root directory is represented by a miniature sheet of paper with the file name on it, and the directories are repre­sented by folders. If you now click on the other drive, to display its calalogue, a second window appears on the screen, overlapping the first, with folders and sheets shown in it. This is now the active window. To close the active window, and return to the previous one, you click on the 'close box' icon at the top left corner of the window.

2 Select a function. Another operation is selecting one of the functions listed across the top of the screen. You do this by moving the pointer to it, an action which results in the appearance on the screen of the pull-down menu for that function, then moving the pointer down the menu list and clicking on the option you require.

3 Move an icon. A third option is moving an icon to a different position on the screen. You do this by moving the pointer to the icon, holding down the left-hand button, and 'dragging' the icon to a new position.

4 Manipulate a window. In a similar way you can alter the size of, and move, the disk catalogue windows. You alter a window's size by clicking on and dragging the symbol shown in its bottom right-hand corner, and you move it by clicking on and dragging the title bar at the top. (In this way you can arrange the Desktop to look the way you want it, and then save your configuration - using the 'Save Desktop' option- so that it automatically appears the next time you run GEM.) Also, if the window is too small to display all its contents, you can 'scroll' through those contents in both horizontal and vertical directions by either clicking on the arrows or dragging the scroll bars displayed at the bottom and at the right of the window.

Most of your work with the Desktop will, of course, be to perform the sort of operations described in the section on DOS earlier in this chapter, such as running applications, changing directories, and copying, deleting, and performing other operations on files. All these are carried out by moving the pointer and clicking.

For example:

• To open a folder, i.e. select a directory and catalogue its contents, you click on its icon. A new set of icons appears in the active window, representing the contents of the selected directory.

• To close a folder, and return to the previous directory, you click on the 'close box' icon in the top left corner of the window.

• To run an application, you click on its icon. This will resemble a sheet of paper, with the name of the appli­cation attached.

• To delete a file, you drag its icon to the trash can, and click on the confirmation message that appears.

• To copy a file from one disk to another you drag it to the drive icon you wish to copy to. To copy a file from one directory to a second directory, you drag it to the folder representing the second directory.

These, and other basic DOS tasks, can also be carried out on whole groups of files and on directories, much more quickly and easily than is possible using the ordinary DOS system of commands. For example, to delete a whole group of files from a directory, you hold down SHIFT while clicking on each file in turn, and then, with SHIFT still held down, drag the lot to the trash can.