Last March we published Al Salt’s plans for adding external RAM to ZX80s. To adapt his Build Additional RAM (SYNTAX 02/03/02) with ZX81s, you can take ne of three approaches. The second two of these plans do not require you to modify the insides of your ZX81.
RAM Decoding for ZX81 Read More »
Sinclair discontinues tech support. Inventory control program sought. Connect full size keyboard to ZX81. Improving ZX80 cooling.
This 8K/1K program uses Crout’s reduction to solve simultaneous equations. The number of variables you can use is limited only by your available memory; in 1K this program solves up to 4 equations in variables
Solving Simultaneous Equations Read More »
DIM arrays can function as a sum-to-memory system found in many calculators. More importantly, it acts as a counter function and can be used where FOR-NEXT loops will not work. Moving Billboard, this illustrates the counter function.
DIM as Calculator Sum-to-Memory Read More »
This program continuously scrolls up to 23 (and more) lines of characters. Do not print more than 32 characters in any PRINT instruction, such as line 150, or the scrolling will fail.
At first glance you might ask, “Is that all there is to it?” I opened the shipping box to find a small black plastic case that obviously plugs into the rear of a ZX80/81 or MicroAce computer.
User Report: Insight’s 16K RAM Pack Read More »
The ZX81 manual states that the three system variables FLAGS, FLAGX and CDFLAG hold various flags to control the BASIC system. But a study of the 8K ROM program discloses 12 separate flags.
The Flags of the 8K ROM Program Read More »
What does your phone number spell out if changed to letters? A friend’s phone number, 438-5678, spells GET LOST. A bank’s auto loan department answers NEXT CAR.
Phone Number Word Generator Read More »
Peter Ulrich, New York, sent corrections for Paul Ezra’s Brownian Motion program (Dec. 81). David Ornstein corrected his New 8K ROM Routine Addresses list (Jan. 82). Jon Passler sent some improvements for his 8K Bar Chart program (Jan. 82) to speed up program execution.
The $20 surplus keyboards from John J. Meshna Jr., Inc., mentioned in the Dec. 81 issue, now come with wiring instructions for ZxX80s.
Surplus Keyboards Plus Directions Read More »
Frustrated by the limitations of 2K RAM, Jim Graham of Oakham, MA, put 6K “under the hood” of his ZX81. He finds it a comfortable compromise, freeing up the edge connector for I/O use. The wirewrapped module consists of four sockets welded together, needs no board modifications and plugs into the existing RAM socket.
