The machine

This page describes what ZX-V is like: what you see on the screen, what you hear, how you control it, and how much room your programs have. It is the same machine in the emulator and in the real hardware.

At a glance#

It starts straight into BASIC, and it also runs native programs written in C for its processor (see the SDK).

The screen#

Two resolutions#

The screen has two modes. Each shows a rectangle of pixels (the paper) surrounded by a coloured border:

Both fill the same area of your TV: a mode 1 pixel is half the width and half the height of a mode 0 pixel. In BASIC, MODE 0 and MODE 1 switch between them. Your programs start in mode 0.

The screen is 640 × 480: around the paper there is a border of 64 pixels at each side and 48 lines above and below.

Colours#

ZX-V has 15 colours: eight colours at normal brightness and the same ones bright (black is the same in both).

Every pixel can have any of these colours, independently of its neighbours.

In BASIC, INK (the colour of text and drawings) and PAPER (the background) take the colours 0 to 7 (8 and 9 have special meanings, explained in the reference), and BRIGHT 1 makes them bright; the graphics commands for games (BOX, DISC, SPRITE...) use the numbers 0 to 15 directly. In those graphics, colour 8 means transparent: the pixels of a sprite drawn in colour 8 let the background show through.

Colour tables. The machine can also change how colours look without redrawing anything: a table says, for each of the 16 numbers, which colour is shown. Programs use this for fades, flashing and colour-cycling effects (in BASIC, REMAP). There are four such tables, and different parts of the screen can use different ones.

Palettes. The 15 colours are the usual ones, but not the only ones: each table has its own palette, which says what colour each of the 16 numbers is, out of 65,536 (in BASIC, PALETTE). So each line of the screen can have 16 colours of your choice, and the whole screen up to 64.

Two pages#

The machine has two video pages, two complete screens in memory. One is shown while the other can be drawn on, and switching between them is instant. Games use this to draw each frame on the hidden page and then show it all at once, without flicker (in BASIC, SCREEN chooses the page to draw on and PAGE the one shown).

BASIC uses the two pages in its own way: page 0, in mode 0, is your program's screen, and page 1 is the editor (in mode 1, or in mode 0 if you choose it in its menu). That is why a program's output and your listing do not mix: when you run a program you see its screen, and when it ends a key takes you back to the editor.

Sprites, tile maps and layers#

There are no hardware sprites: a graphics engine built into the ROM draws everything into the page, very quickly. It can draw:

• sprites of any size, with transparent parts, mirrored, recoloured or scaled up and down;
• tile maps: screens or whole levels built from small square tiles (8 × 8 or 16 × 16 pixels);
• mode 7 floors: a flat picture seen in perspective, for racing games or 3D landscapes;
• lines, filled rectangles, circles, triangles and polygons.

Layers come from the order of drawing: a typical game draws the background of the map, then the sprites, then the parts of the map marked as in front, which can cover the sprites (a tree the player walks behind, for example).

All this is available from BASIC (the BASIC reference) and from C (the SDK).

The virtual playfield and scrolling#

In mode 0 a page can be larger than the screen. The screen is then a window that moves over a bigger picture:

In BASIC, MODE 0, 1024, 192 chooses the size, and SCROLL x, y moves the window. Scrolling is done by the video hardware, without redrawing: the picture moves for free, and a game only draws the column or row of scenery that is about to come into view. The page wraps round at its edges, so a game can scroll for ever.

The machine can also change some settings line by line down the screen: the border colour, the colour table, and which part of the page each line shows. This gives split screens (a scoreboard that stays still while the game scrolls), parallax (distant scenery moving slower), border stripes like those of old tape loaders, and water or road effects. In BASIC this is RASTER.

Text and characters#

Text is written in characters of 8 × 8 pixels: 32 × 24 in mode 0 and 64 × 48 in mode 1. In mode 0, BASIC keeps the bottom two rows for typing answers to INPUT and for its messages, so a program has 22 rows for its text.

The character set has the letters, digits and symbols of a computer keyboard (including £ and ©), sixteen block graphics for simple drawings made of quarter-squares (codes 128 to 143: an empty cell, then ▝ ▘ ▀ ▗ ▐ ▚ ▜ ▖ ▞ ▌ ▛ ▄ ▟ ▙ █, the same as on the Spectrum; the character set explains how they are numbered), and 21 user-defined graphics (UDGs), characters whose shape your program can change. They start out as the letters A to U.

The machine's own messages also have the Spanish letters (á é í ó ú ü ñ ¿ ¡ and their capitals), but they are not part of BASIC's character set. In your programs you type the standard characters only: a letter with an accent, a diaeresis, a tilde or a cedilla typed on the keyboard comes out without it (é as e, ñ as n), ¿ and ¡ come out as ? and !, and other characters are ignored.

Sound#

ZX-V has three sound sources, mixed in stereo:

• The beeper: a simple speaker that is either on or off, like the one in the first home computers. With clever programming it can play surprisingly rich music. In BASIC, BEEP.
• Two AY-3-8912 music chips, the chip of the Spectrum 128 and many other computers and arcade machines of the 1980s. Each one has three voices (called A, B and C) that play notes, plus a noise generator for drums and explosions and an envelope that shapes the volume of a note. With two chips there are six voices at once: music on one chip and sound effects on the other, for example. The second chip starts silent, so music written for one chip plays exactly as on the original.

The voices are spread across the stereo picture (A on the left, B in the centre, C on the right). In BASIC, PLAY plays music written as notes, with up to six voices, and SOUND controls the chips directly. Native programs can also play digitised samples (see the digital example).

The sound comes out through HDMI with the picture and, on the real machine, also through an analogue line output.

Input devices#

• Keyboard. Any USB keyboard. You type as on a PC, with the keys of its layout. On the real machine, Ctrl+Alt+F1, F2 and F3 choose the Spanish, UK and US layouts (the choice is remembered); the emulator uses the layout of your PC.
• Mouse. A USB mouse with three buttons and a wheel. BASIC and C programs get a pointer position in screen pixels (in BASIC, MOUSE).
• Gamepads. Up to two USB gamepads: generic ones and PlayStation DualShock 4 and DualSense (in the emulator, any gamepad your PC recognises). Each has the directions, three fire buttons, Start and Select. The first gamepad also works as a Kempston joystick for programs written for the Spectrum, and BASIC can present a gamepad as keys (JOY).

On the real machine, the keyboard, mouse and gamepads plug into a USB hub.

Ctrl+Alt+Del is the emergency reset: whatever is running, even a program that has hung, the machine goes back to BASIC. A BASIC program is kept; a native program is not.

Memory#

The processor has 520 KB of RAM. Most of it is shared like this:

From BASIC, about 94 KB are free for your program, its variables and its graphics (sprites, tiles and maps): the editor shows the exact number, 93,856 bytes when the machine starts. The rest of the user memory is BASIC's own working space.

A native program takes over the user memory: it can use nearly all of the 248 KB. In mode 0 each video page only needs 24 KB for the screen, so a program that does not use a large virtual playfield can also use the other 72 KB of each page.

The ROM, with the BASIC, takes 512 KB, and the ROM: drive up to 3.25 MB; both are read-only and are not part of the RAM.

Storage and files#

The SD card and the ROM: drive#

The machine has two drives:

• SD:, the SD card, where you load and save. It can be formatted as FAT, FAT32 or exFAT, so you can also use it in your PC. In the emulator, a folder of your PC plays the card.
• ROM:, a read-only disk built into the machine, with the examples. It cannot be written to: trying it gives V Disk error (not allowed).

You use them with the usual BASIC commands: CAT lists a folder, CD changes folder, MKDIR and RMDIR create and remove folders, and COPY, MOVE and ERASE copy, move and delete files (also with wildcards like *.zvb). A path can start with the drive: LOAD "ROM:graphics", CAT "SD:/games". CD "ROM:" enters the ROM: drive and CD "SD:" goes back to the card.

File names can be up to 63 characters long, with unaccented letters, digits and symbols; capitals and small letters count as the same name. Folders are separated with /.

File types#

LPRINT, LLIST and COPY (the printer commands) write to the text file printer.txt at the root of the card.

Spectrum tapes. A .tap or .tzx that you load stays "in the tape recorder": later LOAD "" commands read the next blocks from it, as on a real tape. That is how programs in several parts (a loader, a title screen, the game) load as they did on the Spectrum.

The clock#

ZX-V knows the date and time. On the real machine a clock chip with a battery keeps it while the machine is off; the emulator uses your PC's clock. Files are dated when they are saved, and programs can read the time (in BASIC, PRINT CLOCK 3;":";CLOCK 4 shows the hour and minutes). CLOCK with a date sets it.

If the clock has never been set, the machine works normally and files are dated 1 January 2026.

For measuring time inside a program, the machine counts frames: 60 per second, the same as the screen (in BASIC, TIME). What imitates the Spectrum keeps the Spectrum's time, fiftieths of a second: PAUSE 50 is one second, and the Spectrum's FRAMES variable (PEEK 23672) counts 50 per second, so Spectrum programs time things as they always did.

Languages#

The machine speaks English and Spanish: BASIC's messages (0 OK, 2 Variable not found / 2 Variable no encontrada), the editor's bar and its menu. LANGUAGE "en" or LANGUAGE "es" changes it, and it is remembered (on the real machine, in the clock chip). Keywords are the same in both languages: PRINT is always PRINT.

Programs can read the language and choose their own texts; the Estela game does.

Compared with the ZX Spectrum#

This section is optional reading, for those who know the Spectrum or are curious about it.

What carries over from the Spectrum:

• BASIC programs. The BASIC follows Sinclair BASIC closely: the same numbers, random sequences, error messages and drawing algorithms. Spectrum BASIC programs in .tap or .tzx files load and run, and a program saved as a tape (SAVE "name.tap") loads on a real Spectrum. PEEK and POKE on the Spectrum's screen, attributes and system variables work, and SPEED 0 makes BASIC run at the speed of a 48K for programs that depend on it.
• Screens (.scr and SCREEN$ blocks) load and look as they did, colour clash included.
• Keyboard and joysticks. Programs that read the keyboard with IN see the Spectrum's keys, and the gamepad works as a Kempston joystick or as the Sinclair and Cursor joysticks.
• Sound. BEEP, and PLAY with the 128's syntax, work as on the original; OUT to the AY ports works as on the 128.

What does not: Z80 machine code cannot run, so most commercial games, and BASIC programs that rely on machine-code routines, will not work. ZX-V's own native programs take that role, and they are much more powerful.

The full list of differences, statement by statement, is in the BASIC reference.