Classic Computer Magazine Archive COMPUTE! ISSUE 61 / JUNE 1985 / PAGE 36

Solving Common Printer Problems

Selby Bateman, Features Editor

Few things in computing are as frustrating as a recalcitrant printer. Here are some tips on how to find relief.

At one time or another, every computer user looks at the paper rolling out of a printer and sees something that seems to have been sent from an alternate universe. That's not what I told my computer to print!

Your neatly formatted double-spaced letter is being printed all on one line. Or your beautiful four-color screen illustration is appearing on paper as a series of capital E's. The italics and underlining you've added for emphasis in a report have changed the rest of the words to an unknown foreign language. Or, perhaps most depressing, the paper is simply rolling out of your printer completely blank.

Nine times out of ten, your printer problems won't be mechanical in nature. More likely, they'll fall into one of two major areas, which we may call interface/configuration mistakes and special effects errors.

Problems with interfacing and configuring your computer and printer usually happen during your first attempts to connect everything together. But confusion over special effects—such as boldfacing, underlining, super- and subscripting, and graphics—can happen even to the most advanced computer user.

No matter what the cause of a printer problem, it is a frustrating experience. Yet, with some patience and a thorough understanding of how the computer, printer, software, and printer interface work together, you can unleash all of the power and high-quality performance packed into today's printers.

Whether your computer is a Commodore, IBM, Apple, Atari, TI, or other brand, you should become familiar with how it connects to a printer. Often an extra interface is required to allow an otherwise incompatible printer and computer talk to each other.

A thorough discussion of the many printer interfaces for micro-computers could fill a book. But basically, your data will be sent from computer to printer either in a serial or parallel stream, one bit at a time or eight bits at a time. Most printers use the parallel method. Your computer and printer manuals will tell you which kind of interface to use. But you should also know that some computers require additional accessories to work with certain printers.

For example, the Apple II needs an interface cable and either a parallel or serial interface card. IBM PCs need either the standard printer interface card for parallel connection or an asynchronous serial card. A Commodore 64 can hook directly to Commodore printers to make use of the special graphics symbols and reverse-video characters, but if you want to print special character sets, different type fonts, or foreign language characters, you'll need other printers and appropriate interfaces. Similarly, Atari computers hook up directly to Atari printers, but require the 850 Interface Module or a substitute to work with other printers.

That super-low-priced printer might not look like such a bargain when you arrive home and find that you not only need an additional $35 cable but also a $100 add-on interface. Although most stores selling printers have salespeople to help answer your questions, you should still do your homework with computer manuals, magazines, and books.

To add to the confusion, the application software you want to use—such as a word processor or graphics program—can add its own complications. Unless you configure your system correctly, what you end up with may be quite different from what you want.

For example, let's say your interface automatically sends a line-feed instruction which tells the printer to advance the paper. Your word processing program may already contain a similar command. And the printer, unless adjusted, may automatically add a linefeed as well. As a result, when you try to print out a single-spaced letter, the printer may be following instructions to put two or three linefeeds between each line of print. Conversely, you could also end up with no linefeeds at all. The entire letter might be printed on a single line.

The solution, of course, is to enable or disable the linefeeds, depending on the problem. This may involve opening up the printer or interface to flip a switch, or issuing the appropriate command with the word processor program. The answers are buried somewhere in the manuals.

Once you've got the printer and computer connected properly, you'll eventually want to take advantage of the advanced options which printers now offer. The special effects which turn your system into so much more than a typewriter are theoretically quite easy to control. The complexity stems, once again, from all the configuration possibilities. Versatility has a price.

Let's consider an example using the SpeedScript 3.0 word processor recently published in COMPUTE! for Commodore, Atari, and Apple computers. To underline a word with SpeedScript, you send a control code to the printer which backspaces and underlines after each character. But to Commodore 1525 or 801 printers, the code that most other printers understand as backspace is read as a command to enter graphics mode. Such conflicts are unavoidable, because there are so many different printers and control codes.

Whether you're just getting started with printers or are moving on to advanced printing features, there are a few basic concepts you should understand. If you're having printer problems, check this list to be sure you're familiar with each item. If you're not, invest some time exploring your computer, printer, software, and interface manuals to find a solution.

ASCII (pronounced "AS-Key"). American Standard Code for Information Interchange. A code that uses numbers from 0 to 127 to represent letters, numbers, punctuation symbols, and special control codes. Each code number consists of seven bits (binary digits). An eighth bit may be added for parity (see below). The first 32 ASCII numbers are control codes which can tell your printer to perform actions such as linefeeds, carriage returns, backspaces, and vertical and horizontal tabs.

Commodore and Atari computers use a slightly different form of ASCII which can cause translation problems with some interfaces and printers unless they are correctly configured.

Baud rate. A measure of data transmission speeds, synonymous at lower speeds with bits per second. Computers can send data much faster than printers can produce images on paper. Consequently, the printer and interface must tell the computer to send data in bursts short enough for the printer to handle.

Buffer. In a printer or interface, the memory area in which data is held after being sent from the computer. Printer buffers can be as small as one line of characters or range upward to thousands of bytes of data. If the buffer is large enough, it can hold all of the data you want to print, thus freeing the computer for other tasks while the printer goes about its work. The printer controls the speed at which the data leaves the buffer and is printed on the paper.

Centronics-standard parallel connection. A printer interface which allows data to be sent along separate wires eight bits at a time in a parallel flow. Most printers use a parallel interface to receive data from the computer. Some computers, however, must transmit data through a serial interface (see RS-232-standard serial connection). The Centronics interface, named after the printer company which popularized it, is the most common type of parallel interface on personal computers.

Character set. The letters, numbers, and symbols which a printer or computer can produce. Note that many computers can display characters which the printer cannot reproduce, and vice versa. Some printers are capable of printing foreign character sets when you change the DIP switch settings. (See DIP switches).

Control codes. Nonprintable commands sent from the computer to a printer for special actions, such as backspacing, carriage returns, linefeeds, tabs, and margin settings.

DIP switches (Dual In-line Package). Small switches located on a printer or interface which can control a variety of options, such as baud rates, automatic/manual linefeeds, printing impression levels, international character sets, types of paper, form lengths, line spacing, and other parameters. Some printers and interfaces allow easy access to DIP switches, while others require you to take apart the case.

Emulation. In terms of printers, a mode of operation which mimics another type of operation. For instance, some printer interfaces let a non-Commodore printer emulate a Commodore printer, allowing you to print the computer's special graphics symbols and reverse-video characters.

Escape codes. Control code sequences which let you print certain characters not included in ASCII codes, or which activate special printer features such as boldfacing, italics, expanded or condensed type, and so on. Escape sequences are preceded by the escape character, ASCII 27. These sequences can be sent to the printer in BASIC from your computer keyboard, or by the application software (such as a word processor). For example, ESC H might represent a British pound sign, ESC P might turn on or off the proportional spacing option on your printer, and ESC BS may determine the amount of space between characters in backspacing.

Firmware. Software permanently burned into a ROM chip (Read Only Memory—a cross between hardware and software. Printers contain firmware to control their printing options. Sometimes you can replace this chip with another to add more printing features.

Parity. A way for your computer and printer to check the accuracy of the data being sent. An extra bit is added to the end of a seven-bit ASCII code representing a particular character. The computer checks the extra bit to verify that the data was not scrambled during transmission.

Proportional spacing. Many printers today can vary the spacing between characters, as typesetters do. Typewriters have fixed spacing between all letters. For example, proportional spacing allows more room for a capital M or W and less room for a lowercase i or 1.

Protocol. All the rules and instructions controlling the way in which data is sent and received between the computer and printer.

RS-232-standard serial connection. A type of interface that transmits data along a single wire one bit at a time, or serially. Although most printers use a parallel interface to receive data from a computer, some computers and printers require a serial interface. When all other factors are equal, a serial interface is slower than a parallel interface—but this is rarely important with printers, whose speeds are determined by mechanical limitations anyway.

Tractor-feed. A pair of cogged wheels and guide wires that helps continuous-form paper roll through a printer. Some computers have built-in tractors, and others offer them as options.

Transparency. A mode of operation for printer interfaces in which serial data is changed to parallel data without converting the original values of the data.