SOFTWARE TOOLS

This section introduces you to some of the utilities associated with the development of programs. These program development tools allow users to write and construct programs that the operating system (or another) can run.
EDITORS
Editors are programs used to create documents. They provide facilities for

• Loading/Editing/Saving of source documents
• Change/Replace text strings, characters or words
• Find/Search for text strings, characters or words
• Move/Copy/Delete blocks of text

Editors consist of two basic types, line based and screen based.
Line Based Editors
The line based editor presents a single line for editing. Each line may be called up in turn. The left and right cursor keys may be used to edit the line of text. Standard facilities exist to perform search/find/replace/move items of text. 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. Examples of line-based editors are edlin and vi.
Screen Based Editors
These provide a range of enhanced features, and editing is performed using the whole screen (multiple lines are shown at a time). 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. Screen based editors are normally written for specific types of computers, and thus tend to be more costly, but provide a greater range of facilities, and can be more readily customized for particular applications (such as standard mail/form generation).
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 Word 2000.

THE PROGRAM TRANSLATION SEQUENCE
In developing a software program to accomplish a particular task, the program developer chooses an appropriate language, develops the algorithm (a sequence of steps, which when carried out in the order prescribed, achieve the desired result), implements this algorithm in the chosen language (coding), then tests and debugs the final result. There is also a probable maintenance phase.
When you write a program in a source language such as Pascal or C, the program statements (in the source text file) needs to be converted into the binary bit-patterns which make sense to the target processor (the processor on which the software will be run). This process of conversion is called translation.