Introduction to DTP
The Typewriter
The mechanical typewriter, which originated in the USA about a century ago, represented the first major advance over pen or pencil. Its two principal advantages were that a competent typist could write much faster with a typewriter than with pen or pencil and that the writing produced was consistent and clearly legible. It was not surprising, then, that the typewriter heralded an 'office revolution' in which typewriter manufacturers made fortunes. Typing became part of the school curriculum.Despite its many advantages, the mechanical typewriter suffered one major drawback. As soon as the typist hit the key, the character was on the paper. And when it was on the paper, it was not easy to change it. Even the best typists make mistakes from time to time, and many essential typewriter users would readily admit that they are not good typists. Some corrections, such as substituting one character for another or deleting an unwanted character, were possible using rubbers, correction fluid or chalk-covered correction paper. But corrections made by these means were clearly visible on the final copy, making it appear untidy. Some offices had 'house rules' about the number of such corrections permitted in a document that was going outside the organisation. For example, if there were more than two corrections on the page, the unfortunate typist was compelled to retype the whole page, repeating largely the same keystrokes. More drastic corrections, such as the insertion of a word or, worse still, the insertion of a whole new paragraph, were clearly impossible˜these demanded that the whole document be retyped. What was needed was an automatic typewriter with a memory˜a memory whose contents could be edited˜so that it could do the retyping all by itself. Such a machine is nowadays called a Wordprocessor.
The Wordprocessor
Computers provided the technology needed to do this. Typesetters were the first to avail themselves of it for editing text being prepared for typesetting. It was not until the early 1980s when, as a consequence of the advances in technology which made microcomputers affordable, these facilities began to become available for ordinary office workers, schools and domestic users .Most wordprocessors are general-purpose microcomputers running wordprocessing software. A wordprocessor is a system which has a keyboard more or less like a typewriter's on which text can be typed. As text is typed, it appears on a monitor screen and is also entered into the computer's memory. As more text is typed, the first lines may disappear off the top of the screen, but they are still held in memory and can be brought back on to the screen if required.
The main advance was that the contents of computer memory˜unlike the contents of a sheet of paper˜can be changed easily. On a wordprocessor, a mistake in an earlier line can be easily corrected, even if it involves the insertion of additional text. Whole paragraphs can be inserted, moved, copied or deleted. 'Search and replace' facilities allow the entire document to be searched for occurrences of, perhaps, a repeated mistake, the correct version being substituted automatically. Only when the operator is satisfied that the document, as shown on the screen, is correct, is it printed out.
On early wordprocessors the screen display bore only a passing resemblance to the final printed document. As software and hardware became more sophisticated, 'WYSIWYG' became the accepted standard. This acronym, which stands for 'What You See is What You Get', means that the screen display gives quite an accurate idea of the appearance of the finished document. The displayed typeface may not be the same as that used by the printer, but such effects as bold, underline and italic could be represented on screen as, of course, could the effects of the margins, indents and tab stops which control the position of text.
Another development on later wordprocessors was the provision of automatic spelling checkers. These compared each word typed with a master dictionary held in memory˜any words typed that were absent from the dictionary were brought to the operator's attention. Many systems had a facility which allowed specialised words and names absent from the main dictionary to be entered into a 'user dictionary'.
Wordprocessing is still one of the most widely used applications of microcomputers. It has the advantage of comparative simplicity. But it has limitations. Most wordprocessors cannot handle graphics. They only handle text only using the printer's built-in character sets. At best the printout will look as if it has come off a sophisticated typewriter. And, indeed, the wordprocessor is ultimately just that˜a very sophisticated intelligent typewriter.
Desk Top Publishing
Desk Top Publishing (DTP) takes these ideas a stage further. It uses the microcomputer to create entire documents. Since these may use proportionally spaced text in a range of typefaces, styles and sizes, as well as graphics such as lines, boxes, diagrams and other line drawings and even half-tone illustrations such as photographs, the results, if reproduced on a printer of sufficient quality, may be very professional looking. So DTP allows individuals and organisations, including voluntary and amateur societies, to produce professional-looking newsletters, brochures and posters in-house.DTP is technically a far more demanding application than wordprocessing. A DTP package normally offers the same facilities as a wordprocessor and many more besides, since it handles graphics as well as text and is concerned with the exact positioning of text and graphics on the page. Often in DTP the printer uses its graphics capability to reproduce text using the images of typefaces stored in the computer rather than reproducing its built-in typefaces. (A notable exception are printers using the PostScript page-description language; these carry a wide range of built-in typefaces and print out the page from a 'program' which describes each text line and graphics feature one by one.) To achieve an appearance which approximates to professional typesetting the graphics must be at a resolution of at least 300 dots per inch. Now in wordprocessing, for the computer to tell the printer to print a letter 'W' it normally needs to send the printer only eight bits; in DTP to print a 12 point 'W' at 300 dots per inch the computer may need to send as many as 2500 bits, because it is sending the printer all the data required to build up an image of the character dot by dot.
DTP and the WIMP
In wordprocessing no graphics interface was needed, as the application was in general concerned only with text. But in DTP the page is built up on screen WYSIWYG-style and the user must have the facility to place text or graphics at any position on the page with very high accuracy. Clearly this needed much finer control than could conveniently be provided through the cursor keys. This fine control was possible through the 'WIMP' environment, WIMP standing for 'Windows, Icons, Menus and Pointer'. The Archimedes desktop is a WIMP environment.Windows are areas of the screen set apart for certain applications. Within DTP the window will show a portion of a document. Several windows may be open at one time allowing the user to process more than one document simultaneously.
Icons are small pictures on the screen which represent applications, utilities or facilities. A pictorial representation of an application is easier to identify, understand and remember than a description of the same application.
Menus are lists of facilities or choices available. It is possible for a menu option to lead to another menu called a sub-menu.
The pointer is an arrow moved around the screen generally by a 'mouse' but also possibly by a trackerball or joystick. To select a facility, you move the mouse until the pointer is over the appropriate icon or menu choice and then click a button on the mouse. It is possible for the pointer to take on different forms which can represent the action that will take place when a mouse button is clicked.
How DTP Works
Handling text and graphics to very high accuracy demands highly sophisticated software. It will certainly help you as a DTP user to understand the fundamental principles on which DTP software works.All serious DTP software is 'object based'. That is to say, the software regards the document as being composed of a number of 'objects'. Everything that appears in a document is an object or part of an object. Typically these objects will include text frames and graphics frames and perhaps other types of object. Each object technically enjoys an independent existence, although the same text story may spread through several text frames. The computer keeps a record of each object's size and position. The order in which the objects were created initially determines the sequence in which they appear in the document file and this is also the sequence in which they are drawn on the screen.
Now this sequence is no academic matter˜it has immediate practical importance. Objects may overlap, whereupon the question arises as to whether one object conceals another˜and, if so, which conceals which˜or whether the two overlapping objects are simply superimposed like a pair of transparencies.
In practice, the general rule is that later objects conceal earlier ones. It's rather like pasting snippets into a scrapbook, later ones covering up earlier ones. But there are many exceptions. Usually text cannot be concealed˜it 'flows around' any object placed over it, which is very useful when adding illustrations to a magazine article. Furthermore objects can be made 'transparent' so that they don't conceal other objects beneath them. And facilities are provided to change the positions of objects in the file, so that an item that was near the back can be brought to the front and vice versa.
You can, of course, only work on one object at a time. Working in a text frame is essentially like using a word processor except that there is a wide choice of typefaces, styles and sizes. And re-sizing the text frame will automatically reformat the text so that it neatly fits the space available.
The graphics facilities vary widely from package to package. Some packages offer drawing and painting facilities. But all allow you to 'import' both line art and pixel-based graphics created using art software or image-grabbing hardware. If you're not proficient at computer art yourself, there's a wide range of commercial 'clip art' available with which you can decorate your documents. Once the graphics have been imported into your document they can be scaled, squashed, stretched and cropped to suit your requirements.
Ovation
Ovation is based on the best DTP practice and is fully compatible with other RISC OS packages. Although it is a full-feature DTP system, it has a default text frame and a default paragraph style. So, if you want to write a simple document such as a letter, you have only to start Ovation up and begin typing˜just like a wordprocessor. Indeed, it can double as a wordprocessorŽ˜its text handling operations will be familiar to anyone who has used other wordprocessors.Among its more sophisticated text facilities are a spelling checker with a dictionary of over 60,000 English words and an automatic hyphenation system. (These features require the use of a computer having at least 2Mbyte of RAM.)
Whilst Ovation's built-in graphics creation tools are limited to straight lines and frame borders, this does not really matter since all RISC OS users have access to Acorn's sophisticated Draw and Paint applications and Ovation can handle any graphics produced by either of these. Remarkably even Draw files containing 'text area objects' can be imported into Ovation and scaled and cropped as required. A selection of clip art is supplied and a variety of further clip art in both sprite and line drawing form is available from software suppliers.
Ovation uses a hierarchical object structure in which objects created inside other objects become 'nested' in them and are automatically moved or copied with them. This makes the creation and layout of diagrams and tabular matter exceptionally straightforward. Whether your document is a single-page letter or a multi-page, multi-column newspaper, Ovation provides a simple route to professional looking documentation.