an attorney builds his first computer

Dennis Allison reply points out BASIC limitations

[author : Lichen Wang] #Listing #Assembly

Extract : «  (reprinted with permission from Homebrew Computer Club Newsletter)

If your 8080 microprocessor system is not equipped with non-volatile memory, you probably have to reload the memory from time to time. To read the Intel hex-format paper tape, you need to key in a loader of some eighty-odd bytes long. This is rather tedious and often leads to error. Altair BASIC has a bootstrap loader of twenty or twenty-one bytes long. In principle, you can use this bootstrap to load in your own loader which will then load in your program. I coded one myself, and what comes out is a bootstrap sixteen bytes long. This is still too long—maybe our professional experts can make it shorter. For the time being, you are welcome to copy mine. [...]  »

[author : Tom Pittman] #Listing #Assembly #Programming

Extract : «  (reprinted with permission from Homebrew Computer Club Newsletter)

These are some programming tricks I have accumulated over the years which can often save a byte or two in 8080 programs. Because of the peculiarities in the instruction sets, only a few of these also apply to 6800 programs and are so noted. Many of these tricks are widespread lore; some I have never seen elsewhere. I hope they can help you as well. [...]  »

[author : Bill Thompson] #Listing #BASIC #Book

Extract : «  Following is a program and sample run of a simple expression evaluator, written in BASIC. The program uses a transition table to "crunch" an expression. I have restrained myself from numerous embellishments which have occurred to me as I worked on the program—had I started on that route I would soon have succeeded in writing a BASIC interpreter in BASIC! Nevertheless, I do suggest that the beginner who wishes to learn enough to write a compiler or an interpreter will find it particularly helpful to write this routine in assembler code. If you have access to a version of BASIC with strings, add some of those embellishments I left out, such as program storage, exponential functions, and assigning an expression to a variable. All of these will get you into the program, and hopefully into your own language. [...]  »

[author : Fred. J. Greeb] #Listing #Assembly #Programming #Office

includes general comments, user documentation & extensively annotated source code

Extract : «  The text editor program is a strong/line oriented program written in 8080 assembly language. The program is designed for use in the development of source programs to be processed by an assembler or compiler, or for general purpose ASCII file generation. 29 separate commands are recognized by the program

The editor does not require line numbers to be present in the ASCII file. It has the capability to search for and locate any string of valid ASCII characters in the file, irrespective of their location within a line. Lines can be added, deleted, replaced, modified, or printed with simple input commands. Once initialized, the program contains self protection features so that it cannot overwrite itself.

HARDWARE REQUIREMENTS-The program occupies approximately 2.5K words of memory, plus memory space for the file being edited. An additional 128 words of memory are used for the 8080 stack. Peripherals supported are a TV-Typewriter, Baudot teletype (output only), and a cassette tape. Several of the driver routines for the peripherals are contained in the system monitor ROM, and must be supplied externally for conversion to other 8080 systems. [...]  »

[author : Erik Mueller] #Game #Listing #BASIC

[author : Ron Santore] #Game #Listing #Assembly

[author : Charles Skeldon] #Listing #Assembly #Programming

Extract : «  I have noted some errors and possible improvements in Arnold's and Whipple's Tiny BASIC Extended (TBX) [please see Dr. Dobb’s Journal Vol. 1, Nos. 1 & 2].

A minor reduction could be made at the entry point of the main program by eliminating a jump. The end of the error routine duplicates the initialization, so it could be shortened. These two routines follow (in split octal): [...]  »

[author : Lichen Wang] #Listing #Assembly #Programming

Extract : «  I have a few miscellaneous items related to the "Palo Alto Tiny BASIC" published in Dr. Dobb's Journal, Vol 1, No. 5. First of all, there are a few misprints (my fault). On page 13, right column, second line from the bottom, the minus sign should have been a back arrow The same misprint appeared on page 14, left column, lines 15 and 16. [...]  »

[author : Erik Mueller] #Programming

[author : Video Terminal Technology staff] #Display

Extract : «  Video Terminal Technology announces a new video computer terminal with all the features of a professional terminal at a hobbyist price. The VT-4000 video terminal displays 48 lines of 64 characters in a 5x7 font. This provides the capability to display 3076 (3K) characters simultaneously—8 times the standard tv typewriter's 16 lines of 32 characters. [...]  »

[author : Matrox Electronic Systems] #Memory #Display

[author : Jim Day] #Encoding #Display

Extract : «  Figure 1 shows a typical dual-case TVT alphabet, each letter of which is generated via a 7 by 9 dot matrix. If two "undots" (using the terminology of Don Lancaster's TV Typewriter Cookbook) are appended following the seventh dot position of each line of each letter, each letter will require 9 dots of width on the tv screen. The alphabet could be stored in a ROM, the dot pattern of each letter being represented by 9 bytes. Figure 2 shows 9 bytes representing the letter "A". Figure 3 shows how the string "even spacing" would be displayed using this alphabet. Notice how much empty space appears on both sides of the letter "i". This is because each letter is centered left-to-right in the matrix which is 7 dots wide. [...]  »

[author : David Valliere] #Display #Electronic

Extract : «  The TVT-II memory is continuously being addressed through nine address lines to generate the video data used by the teelvision display. The tenth address line (A9) is used to switch from page one to page two. By using the A9 address line for continuous addressing, the TVT-II can be modified to display 64 characters/line. Since the additional 512 characters being displayed are what used to be page two, additional memory will have to be added to provide storage of a second page. [...]  »

[author : Glendon Smith] #Electronic #Display

complete design & implementation details, including complete schematics

Extract : «  The tv display described in this report is intended for direct plug-in to the bus of an Altair 8800 or other similar microcomputer. The circuits could be adapted to CPU's other than the 8080.

This display differs from the tv typewriter circuit in three major areas. 1) The screen refresh memory is connected to the bus when it is being loaded or altered. 2) The display can produce 128 characters stored in a Motorola ROM (12 lines of up to 32 characters each) and/or up to 128 graphic shapes (8x8 picture elements) stored in RAM (24 lines of 32 shapes). 3) A crystal-controlled commercial sync generator IC is used to provide vertical interlace and a jitter-free display. [...]  »

[author : Southwest Texas Products Corporation] #Display

#Memory

#Interface

#Printer

[author : Western Data Systems staff] #ComputerKit

Extract : «  The Data Handler is Western Data Systems new product. It's a microcomputer using the MOS Technology 6502 microprocessor with the latest state of the art technology producing a high performance microcomputer at a low price. [...]  »

[author : Jim Day] #Microprocessor #Computer

#OtherMagazine

WE WANTED TO INCLUDE MUCH MORE IN THIS ISSUE THAN WE COULD AFFORD. PART OF IT WILL JUST HAVE TO WAIT FOR FUTURE ISSUES. THE REST OF IT (ALONG WITH STILL OTHER USEFUL TIDBITS) HAS BEEN PUBLISHED ELSEWHERE:

Southwest Texas Products Corp., 219 W. Rhapsody, San Antonio TX 78216, has put out the first issue of their Newsletter, a 49-page, loose-leaf job. We would like to applaud their work and their approach to hobbyist software. This issue of the SWTPC Newsletter contains extensive information on 6800 software, including some "bug" notices and corrections, a list of available 6800 games, some hardware notes and schematics, and complete listings of:

A Black Jack game-playing program (9 pages, full-size, hex-coding only)

A Memory-Dump program (2 user-documentation pages, 2 pages of unannotated source code)

A 1.3K Editor (3 user-documentation pages, 6 pages of unannotated source code)

A 3.15K Micro BASIC (5 user-documentation pages, 15 pages of unannotated source code)

The Editor was written by Robert Uiterwyk, 4402 Meadowwood Way, Tampa FL 33624. Micro BASIC was done by Uiterwyk and Bill Turner. We have spoken with Mr. Uiterwyk several times (we originally planned to publish Micro BASIC in this issue), and think "his head's in the right place." He and his associates are actively pursuing the production of free and very inexpensive systems software for hobbyists. We would like to praise their efforts and urge them onward.

The July issue of People's Computer Company, Box 310, Menlo Park CA 94025, contains its usual load of exciting items, notably including:

Lichen Wang's Star Trek, written for Palo Alto Tiny BASIC [DDJ, Vol. 1, No. 5] (We wanted to publish it in this issue of the Journal but didn't have room.)

An update of the comprehensive list of computer stores in the May issue of PCC.

An update of the list of computer clubs that was given in the preceding issue of PCC.