CIGAL Reference Manual, Chapter 1 (Topics): egamode
In “EGA” graphics mode the screen is made up of 640 x 480 “pixels” (or dots). Each pixel can be assigned any one of 16 colors. In graphics mode, text is generally restricted to just the bottom five lines on the screen in order to avoid overwriting the graphics image. If you use a command that prints more than 5 lines of output, the printing will pause after every 5 lines to give you a chance to read. To continue, you should press the <RETURN> key or the left button on the mouse and to stop printing, press <ESC> or the right button on the mouse.
The graphics mode menu is generally displayed along the right margin of the screen. To use a menu command you “touch” the menu, either by pointing with the mouse and pressing the left button, or by moving down the menu list with the up and down arrow keys and then pressing <RETURN>. To draw on the screen, use the SKETCH command. In SKETCH, you draw by moving the cursor with the left button pressed. You can make a jump to a new position (without drawing) by moving the cursor and then pressing the right mouse button. The <DELETE> key erases the last line segment, and <INSERT> gets it back. The <END> key erases all the way back to the last jump, and <HOME> “un-erases” all the way to the next jump. Touch the color bar to change the drawing intensity. See the INPUT and OUTPUT commands for how to read and write graphics data. If you ever lose the menu display you can get it back by typing the MENU command.