Introduction

The emulator described here - "ZCE" - is a "command-line" edition, which means a "K>" prompt is sent to stdout, and input is expected from stdin. Graphics may be sent to stdout as Sixel graphics. These can be viewed using newer XTerms and classical DECterms. The Sixel graphics appear between command line prompts, so not in a separate window. Sixel graphics files may be viewed by just using "cat" under Unix, and "TYPE" under VMS. The image below is displayed using JavaScript [if enabled in the browser].

Features

• When the emulator is started, an ASCII BASIC file may be run, or a "K>" prompt is displayed and emulator commands [in lowercase] or BASIC commands [in uppercase] may be entered. LPRINT and LLIST write to stdout; "copy" and "scopy" are available to display the screen in ASCII or Sixel graphics. INPUT and INKEY$ read ASCII from stdin; with INPUT, the "K>" prompt changes to "L>" and "L$>" for numerical and string values, respectively.
• Built-in "compiling" of ASCII source files or a direct command from the command line with normal syntax checking. For example, the response to "PRINT ++2" is "PRINT <S>++2". [Compiling entails converting BASIC keywords to their one-byte "token"s, and converting numbers to their five-byte floating-point representations.]
• 48K program space.
• Optionally case sensitive input and output.
• Reading a binary file to location 8192 [0x2000], for 8-bit character string information or the output of an assembler.
• Hires plotting to graphics screen at address 10240 [0x2800] (the display pointer can be changed at the command line).
• Access to the command line argument.
• Reading of environment variables, and strings may be output to a file, which exports the strings to environment variables when "source"d.
• Exchange strings of information via a socket.
• BASIC lines with identical line numbers is no issue, so renumbering is hardly needed. Empty lines, and comment lines with "#" are also allowed.
• Merging of BASIC files.
• Line number tracing.
• Works under Unix and VMS.
• Some additional commands to inspect and call routines in the ZX81 and the Z80 processor environments. For example, an assembly routine may be single-stepped. The dz80 disassembler by Mark Incley is integrated so that the instructions to be executed are shown as well as register contents (see below for an example).
• Reading and writing of .bmp files - for example, created with the "zxcity" demo:
  
  
• Most action games use the keyboard and the screen in such a way that nothing seems to happen when such a game is loaded in this emulator. A Unix signal may be sent to the emulator so that the screen is shown, but such games are better played on a "real" emulator. See also the link below for an adaptation of xz81 that outputs Sixel graphics, including hires graphics.

Some Applications

1K Chess [after a match against itself :)]

This famous program was relocated to address 0x2000 and made accessible from BASIC. The board may then be displayed in different ways [although that should perhaps not be done...]. Here the AI routine, change of player, and the [Sixel] display of the board were called in a loop.

Download the board as a Sixel graphics file.

Star Trek [1973 version]

This famous program was ported to ZX81 BASIC; currently it has a line count of about 700, and it needs more than 16K RAM. Here is an example run in command-line mode:

An HTTP Client

Here is a session with a very basic HTTP client:

Server-side ZX81 Scripts

Click here for the listing of a server-side script. A$ may be assigned by appending the argument to the url such as here [seconds of the real-time clock as an example]. And click here for the listing of a simple message board :)

Example of single-stepping the ROM

k> r0     # zero all registers
k> z      # show registers
*pc: 0000  [pc]:   d3
 sp: 0000  [sp]: fdd3
  a:   00     f:   00
 bc: 0000    de: 0000    hl: 0000
 ix: 0000    iy: 0000
k> b0x416 # set breakpoint in initialization
k> j0     # run from start
 pc: 0416:     cd0702:  call  0207
 sp: fffd  [sp]: 3e00
  a:   1e     f:   40 z
 bc: 00fe    de: 0000    hl: 4099
 ix: 0000    iy: 4000
k> s      # start single-stepping
 pc: 0207:     213b40:  ld    hl,403b
 sp: fffb  [sp]: 0419
  a:   1e     f:   40 z
 bc: 00fe    de: 0000    hl: 4099
 ix: 0000    iy: 4000
k> s
 pc: 020a:         7e:  ld    a,(hl)
 sp: fffb  [sp]: 0419
  a:   1e     f:   40 z
 bc: 00fe    de: 0000    hl: 403b
 ix: 0000    iy: 4000
k> s
 pc: 020b:         17:  rla   
 sp: fffb  [sp]: 0419
  a:   40     f:   40 z
 bc: 00fe    de: 0000    hl: 403b
 ix: 0000    iy: 4000

Under development - I

Extended memory: some Z80 instructions such as call and ret were modified to allow switching to another bank, based on a bank indicator array. Emulator Z80 code, previously located in the first 64K has now been moved to above 64K. Certain POKEs at strategic positions allow PEEK, POKE and USR in another bank from within BASIC. For PEEK, this works because the LD A,(BC) was modified to look at the specified bank. Developing code is a bit difficult, because the indicator array has to be set manually.

Under development - II

See here, here, and here for examples of using the Mini-XML library for loading and saving programs: click right mouse to view the xml source. The first example is interpreted by reading it into the emulator; the second is a hexadecimal-only memory representation; the third shows the memory's contents after the example is run. The second form is useful if the memory is mainly occupied by machine code.

Download

Unofficial Versions of the z81 Emulator

Download version 2.2 with extensions to the z81/xz81 emulator with hires and Sixel graphics, or version 2.3 with these extensions, and special options for running ASZMIC.

Unofficial Version 2.2.0 of the sz81 Emulator

Download extensions to the sz81 emulator for hires graphics, Chroma, ASZMIC, and ZeddyNet support.

JSZeddy: a ZX81 emulator in JavaScript

JSZeddy and its manual.

The ZX Font, for HTML Screen Output

1234567890123456789012345678901234567890123
the quick brown fox jumps over the lazy dog
THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
THE LAZY DOG JUMPS OVER THE QUICK BROWN FOX
Inv.nums: áâãäåæçèéà
Specials: 12345678901234567
Specials: "$:?()><=+-*/;,.£
Inv.spcs: ÒÔêïØÙîìíÛÝÚßëÜÞ¤
Graphics: ° ± ² ³ ´ µ ¶ · ¸ ¹ º
Graphics: À Á Â Ã Ä Å Æ Ç È É Ê
Extra: !#%&'@[\]^_`{|}~
Extra: 1234567890123456

The Computer Image

Download the image as a Sixel graphics file.

Contact

Last updated February 10, 2015