TRS-80 strings. (Printers) (evaluation) Stephen B. Gray.
Pausing at bar 64 of the Tandy concerto for TRS-80 and users' orchestra, we see onstage the SCM L-100 daisywheel printer, Radio Shack's own color ink-jet printer and screen dump, and a short program that calculates large factorials, such as 50! and 100! SCM L-1000 Printer
The Smith-Corona letter-quality TP-I daisywheel printer was reviewed here (Nov. 1982, p. 310) as a good machine with a slow speed that matched its low price. Its successor, the TP-II, was seen by John J. Anderson (Jan. 1984, p. 234) as "redressing some of the problems of the original model," producing "impeccable ... harcopy output," but still slow, unidirectional, and noisy.
The TP-II was an interim model, introduced in September 1983, and replaced in January 1984 by the the TP-22 Plus, which almost immediately was renamed the SCM L-1000, apparently in an attempt to change the image of the printer and/or the manufacturer.
The TP-II Plus, also an interim model, carried a suggested retail price of $645. The L-1000, which SCM assures me is exactly the same printer except for some cosmetic changes, is $545. SCM says the $100 reduction is due to their "making more of them, and also to market demads." Translation of the second part: competition from $500-or-so daisywheel printers from the Orient forced the price down.
The L-1000 (Figure 1) improves even more on previous models. It now prints bidirectionally, and can do so in three pitches: 10, 12 and 15 characters to the inch.
It's still slow, at 12 cps, but provides handsome output at a low price; it can be bought in New York City for less than $440.
The print buffer has been expanded from 256 charactrers to 570; if you turn off your TRS-80, the L-1000 will keep on printing for about 20 seconds. L-1000 Printwheels
Five easy-to-change 10-pitch print wheels are available, along with five 12-pitch wheels, and one for 15 characters to the inch. The one for computer use is the ASCII Tempo 10/12 wheel, which includes greater-than, less-than, backslash, up-arrow and other such characters. This particular wheel is designed to look good at either 10 or 12 cpi (Figure 2).
Tempo 10 is a 10-cpi non-ASCII printwheel, with a nice modern looking font that is slightly different from the ASCII Templo 10/12. Regency 10 is a modern version of standard pica.
Any of the SCM printwheels can be used at any of the three different pitches. The 15-cpi pitch is rather tight, but permits squeezing the maximum amount of text onto a line. SCM Ribbons
Three different types of easily changed ribbons are available for the L-1000. The least expensive (around $4.75) is a reusable fabric (nylon) ribbon, which gives good printing. The non-reusable multistrike mylar film ribbon costs more (about $9.50), but gives better printing; the film is moved over just enough each time so that the next character uses some of the same area as the previous one.
Single-strike film gives the best printing, and costs $4.50 or so. This one-time film provides a new print area for each character, thus providing top-quality sharpness and clarity. It costs less than multistrike film because it provides far fewer impressions per inch.
The L-1000 comes supplied with a multistrike mylar film ribbon. Software-Controlled Features
The L-1000 has 19 special control codes for turning a variety of features on and off. For example, underscoring can be performed three ways. To underscore one character, transmit the character to be printed, then the backspace codes BS, followed by the underscore character.
To underline individual words--but not the spaces between them--send an ESC-Z code; stop the underlining with ESC-R. To underline everything, send ESC-E. ESC is sent as CHR$27).
The left margin can be set by ESC-9 and released by CAN. Tabs can be set with ESC-1, removed individually by ESC-8 or all together with ESC-2. After the tabs have been set, ASCII code HT will move the printwheel carrier to the next set tab to the right.
Bidirectional printing can be enabled with one code and disabled by another. Pitch can also be changed from the computer, by sending three CHR$ codes: CHR$(27) for ESC, CHR$(31) for setting pitch, and CHR$(8) for pitches 10, 12, or 15 cpi, respectively.
Other control codes set the top and bottom margins, as well as page length.
Under a back panel plate are 14 DIP switches that control other features, such as character length, parity, baud rate, and whether or not a carriage return is accompanied by an automatic linefeed. For the TRS-80, all you need do is turn on that last one, otherwise the paper will never space up.
A Top-of-form switch permits positioning continuous-form fanfold paper and responding to the ASCII Formfeed character, chr$(12), to advance the paper to the top of the next sheet. This requires a tractor feed, available at $149 list.
Both RS-232 serial and Centronics parallel interface ports are provided. The serial interface has both hardware and software handshake protocols. User Comments
I've been using the L-1000 since it was the TP-II Plus (and the TP-II long before that) for printing out this column and am quite satisfied with it. There is only one problemf now that it's bidirectional, it prints a little too fast for me to be able to stop it every time just where I want to by raising the cover, which activates the "pause" switch.
If you're printing the same type of material over and over, you eventually learn how to set the controls to print exactly what and where you want. But if you do a variety of printouts, you may not be able to get each one right the first (or second) time, every time. So it's handy, if you are printing only one or two of something, to be able to stop the printing and move the paper up or down to change where the next line will appear.
This is impossible, of course, with a fast printer. But with a slow one, you can catch it at the end of a line, in the case of the TP-II, by just raising the cover. The L-1000 requires a faster hand, which is one way of keeping in training for video games.
The TP-II had one thing I wish the L-1000 had: a hinged plexiglas cover over the platen which functions as a dustcover when the printer isn't being used. Color Ink Jet Printer
Computer printout in color is a complicated process, and only recently has become available at prices the personal computer owner could reasonably afford.
Up until not long ago, the only color printers available for personal computers used multicolor ribbons with noisy mechanisms whose many moving parts often wore out too fast. Long printing times and unimpressive color reproduction were additional drawbacks.
Ink jet printers have been around a while. But there were several interrelated problems involving ink, nozzles, and printing speeds. For example: how to make the ink dry fast enough on the paper so it doesn't smear, and yet not have it dry up inside the printer.
Several ink jet printers that solve most or all of the problems have become available recently, including one from Radio Shack. CGP-220 Seven Color Ink Jet Printer
Radio Shack's TRS-80 CGP-220 Color Ink Jet Printer (Figure 3), priced at only $699, prints in seven colors, both text and graphics, so quietly you can barely hear it. The parallel interface permits using any TRS-80 computer; the serial interface is compatible with the Color Computer.
In graphics mode, the CGP-220 prints with a maximum resolution of 640 dots per line. Text is printed at 37 characters a second, 12 to the inch, on a 7-by-5 matrix.
A screen dump utility allows the CGP-220 to create four-color printouts of color screens produced by graphics programs on a 16K Color Computer.
The CGP-220 contains two ink packs, which are said to print up to 4 million characters: the black pack is $9.95; the three-color pack is $14.95. The printer takes roll paper ($9.95 for three) or sheet paper (6.95 for 250 sheets; this is a plastic-impregnated paper that the ink doesn't soak, as it usually does into bond paper). Text Mode
If you want to check out the ink jet printer, turn the power off, press the FEED switch, turn the power back on, and all the standard alphanumeric symbols will print, each line in a different color, until you turn the printer off.
Connect the CGP-220 to a "black-and-white" computer, such as the Model 4, and it's in text mode when you turn it on. You can use all the features of the printer from within a Basic program by using any of 14 control codes which control the mode selection, linefeed, carriage return, elongated characters, dotpitch selection, printhead positioning, character repetition, color selection, etc.
Characters can be printed twice as wide as normal with control codes 27 and 14. Most multiple-code sequences begin with 27, the ESCape code. Code 14 starts character elongation; code 15 terminates it. Enter these lines, as printed by a CGP-220: 10 LPRINT "NORMAL CHARACTER" 20 LPRINT CHR$(27); CHR$(14); 30 LPRINT "ELONGATED" 40 LPRINT CHR$(27); CHR$(15); 50 LPRINT "BACK TO NORMAL" AND RUN THE PROGRAM, and you get NORMAL CHARACTER ELONGATED BACK TO NORMAL
If you had wanted to print that three-line message in red instead of black, you'd have to add this program line:
5 PRINT CHR$(27); "T"; CHR$(49) where "T" --or its equivalent CHR$ (84)--selects colors, and 49 is the code for red. To print the message in green, use code 50; in yellow, code 51; etc.
Normally, don't pitch is set at a 4:3 ratio, meaning the printed characters are slightly higher than they are wide. To print characters that are as wide as they are high with a dot-pitch ratio of 1:1 as in the center line of these three: NORMAL DOT PITCH 1:1 RATIO DOT PITCH BACK TO NORMAL DOT PITCH YOU NEED CONTROL CODE 78 (OR N) to start them, and code 80 (or P) to return to the normal 4:3 pitch. Bit Image Mode
The CGP-220 prints in two different graphics modes with different resolutions; you have to no pre-defined characters, so you have to program the printhead to print dots where you want them and in the color you want them.
In Bit Image mode, you can address 640 dots on a horizontal line and seven dots vertically at a time, for a total of 4480 dots. First you send the printhead to a specific dot-column, then you tell it which of the seven vertical dots to print. You can print them in any combination. The dots have binary address numbers: 1, 2, 4, 8, etc. So you add up the numbers of the dots you wish to print and put the sum in the program line that specifies which dots are to be printed where.
Colors are designated in Bit Image mode the same as in Text Mode.
The CGP-220 manual provides brief examples of printing in the Bit Image mode, but doesn't mention the obvious: you could go out of your mind programming the screenful of dots required to create full-resolution color graphics.
What is needed is some sort of each-a-sketch program, to let you easily create graphics with the CGP-220. This can be done indirectly with the $34.95 Micropainter program. However, Micropainter is actually a coloring book program; you load one of eight pictures into the computer, and "paint" it in, which isn't very creative. Color Scan Mode
The CGP-220 Color Scan Mode "is somewhat like the Bit Image Mode, but it allows for greater manipulation of color, requires a great deal of attention to detail, and consumes a lot of memory space," according to the manual.
Just to be different (and confusing), Color Scan Mode involves dots horizontal rows with each line of 640 dots divided into 80 dot-row of eight dots each.
The eight dots per dot-row also have binary address numbers; just as in Bit Image Mode, so you add the binary numbers of the dots you want to print. In Color Scan Mode, you control the colors of the individual dots.
The manual includes a five-line program that prints three rows of dots with three color dots in each dot-row and all the other dots black.
Color Scan Mode is even more complicated that Bit Image Mode and needs even more some way to simplify creating graphics. Color Computer Screen Dump
With Radio Schack's $9.95 Hi-Res Screen Print Utilities program, you can reproduce graphics from a 16K Color Computer (;igure 4). One catch is that the graphics must have been created with a program in Basic, so you can't dump the display of the Color Computer games, which are on machine language ROM Program Paks.
The screen dumps are in black and white or in four colors. You have the option of selecting the background color (green, black, or white); the three other colors are different for each background color.
For black-and-white screen dumps only, any Radio Shack (or compatible) dot matrix printer with full bit image capabilities can be used, including the LPVII, LPVIII, and DMP 100, 110, 200, 400, and 420. CGP-220 Bottom Line
Although the TRS-80 CGP-220 Color Ink Jet Printer is a fascinating machine, its graphics modes are just too complicated to use, and the screen dump is limited to Basic programs. Also, there is a lack of some features found in other dot matrix printers in the same price range, such as boldface, italics, proportional spacing, and underlining.
So, unless you're a hardcore printer enthusiast, or a die-hard graphics fan, the CGP-220 may not be for you--at least not until the graphics modes are easier to use and the screen dump works for machine language programs too. Short Program 48: Factorials
From Burlington, IA, Francis S. Horton wrote a letter that has this fine bit of computer-generated art on the first page:
Francis says he has "been a TRS-80 'freak' (and booster) since 1978." Then he says, "A few years ago, after discovering that a TRS-80 'overflows' before getting very far with factorials, Donald Wemmis, a mathematics and programming instructor at Southeastern Community College in Burlington, wrote the following program. To the best of my knowledge it has no upper limit, it you have a few days to do without your computer while it makes the computations and prints the answers. I've seen the results of calculating the factorial of 1000. I've forgetten the number of digits in the answer, but you wouldn't believe me anyway. Here 'tis set up to calculate 50 factorial (Listing 1). Just raise the limits and go for broke."
To make the program calculate 100 factorial, change the 50 in line 20 to 100 and change the 100s in lines 10, 30, 40, and 60 to 200. (Do not change the 100 in line 80 to 200.)
The letter ends with another nice piece of dot-matrix art:
Products: SCM l-1000 (computer apparatus)
CGP-220 Seven-Color Ink Jet Printer (computer apparatus)