These types of editors are cheap, provide a basic set of functions, and are reasonably small in terms of code size. A limited number of commands are offered that people can quickly learn. These provide a range of enhanced features, and editing is performed using the whole screen, eg, more than one line. The cursor may be moved in any of the four directions, provision is made for scrolling the text when the cursor exceeds the boundary of the display window. The screen editors may be command driven, where all functions to be performed are entered as commands on a single command line, or may be key generated, where pressing certain keys perform the desired function.
Command driven editors tend to be the easiest and quickest to learn.
By displaying more than one line at a time, screen editors facilitate the speedy modifications required for source documents. Examples of screen based editors are Notepad, WordPad, and Write. There is also a probable maintenance phase. This process of conversion is called translation . Assemblers are programs which generate machine code instructions from a source code program written in assembly language.