While the 4K Integer Basic in the Sinclair ZX80 is adequate for many applications, most programmers will eventually feel a hunger for more power. True, advanced functions can be simulated by way of subroutines, but such measures eat memory at an alarming rate. Enter the 8K Basic ROM. The chip costs a mere $39.95, which is an extremely low price for any ROM. Some versions of Basic are sold for over $200 on disk. Sinclair gets four stars for not robbing its customers.
Plugging In
Installing the ROM chip requires opening the Sinclair. Most owners have probably already done this out of curiosity and learned that nothing disasterous follows. One really has to go out of his way to hurt the little critter. The only problem is dealing with the plastic pins which hold the case together. Once the case is open, the old ROM has to be removed. This requires some patience. If a chip is pulled with unequal pressure, the pins can be bent. It’s best to keep the old ROM intact, for reasons that will be covered later. The new ROM is installed by lining up the pins and exerting gentle pressure. Next, a new keyboard overlay is put in place. This overlay contains letters, numbers, keywords, graphics symbols and functions, with color coding to aid the confused. Once the ROM has been tested by powering up the computer, the case can be replaced.
Features
With the ROM installed, the Sinclair has floating point capability. It can handle decimals with nine-place accuracy. Other added functions include string and numeric arrays of any dimension, trig functions, and extended string functions. The PLOT and TAB commands allow formatting of text and graphics. Unfortunately, the proposed DRAW command, which would have drawn a line between any two sets of coordinates, was not included in the final version of the Basic.
As before, keywords are obtained with a single stroke. By hitting the FUNCTION key, the user can also obtain functions with one keystroke. Don’t get excited about the commands FAST and SLOW. The Sinclair already operates in the FAST mode. The SLOW mode (to eliminate flicker of the display) only works on the ZX 81, which is not yet available in the U.S. There is a SCROLL command, which moves the screen display up one line. The computer will still crash if you attempt to write beyond the screen.
Several commands have been provided for use with the printer Sinclair plans to introduce. The user will be able to send listings to this printer and to print the contents of the screen. For interactive programs, there is an INKEY$ command. This reads the keyboard without requiring NEWLINE. The pause command sends the contents of the display list to the screen and waits a specified amount of time. This allows for limited animation, but still produces a flicker. All in all, the 8K Basic greatly expands the potential of the Sinclair.
Compatability
The 8K ROM contains an improved set of tape routines. While this means that loading and saving should be less hassle, it also means that you can’t load old-ROM tapes into a new-ROM machine. And even if you could load such programs, they wouldn’t run. This means most users will be doing a lot of translating. Two major differences must be kept in mind. First, many programs took advantage of the Integer Basic, ignoring the remainder after division. To simulate this in the new Basic, use the INT function. Secondly, where the Integer Basic ROM used minus one for true when evaluating logical operations, the 8K ROM uses positive one. Any calculations based on logical operators will require a sign change during translation.
Ideally, it would be nice to be able to switch from one ROM to the other. Someone is bound to produce such a switch in the near future and many enterprising hobbyists are likely to design their own. While such a switch would clobber anything in memory, it would allow loading of either flavor of tape without pulling and replacing chips. For this reason, it is advisable to hold onto the old ROM.
The most noticable difference between the ROMs occurs when you try entering a 1K program. The new ROM uses about 100 bytes more of RAM than the old ROM. Most programs that fit into 1K before won’t fit now. To get any value out of the new Basic, a user should have at least 2K, preferably 16K.
So, if you are feeling limited by 4K Basic, and either plan to expand memory, or already have, then the 8K Basic ROM is an excellent way to extend the capabilities of your Sinclair. The 8K Basic ROM is available for $39.95 plus $4 shipping from Sinclair Research Ltd., 1 Sinclair Plaza, Nashua, NH 03061.