Sinclair ZX81 character set

The Sinclair ZX81 character set rendered in the system font.
Language	English withpseudographics
Created by	Sinclair Research
Preceded by	ZX80 character set
Succeeded by	ZX Spectrum character set

TheZX81 character set is thecharacter encoding used by theSinclair ResearchZX81 family ofmicrocomputers including theTimex Sinclair 1000 andTimex Sinclair 1500. The encoding uses onebyte per character for 256 code points. It has no relationship with previously established ones likeASCII orEBCDIC, but it is related though not identical to thecharacter set of the predecessor ZX80.

The character set has 64 unique glyphs present at code points 0–63. With themost significant bit set the character is generated ininverse video; corresponding to code points 128–191. These 128 values are the only displayable ones allowed in the video memory (known as the display file). The remaining code points (64–127 and 192–255) are used as control characters such as 118 fornewline or, uniquely toSinclair BASIC, for keywords, while some are unused.

The small effective range of only 64 unique glyphs precludes support forLatinlower case letters, and many symbols used widely in computing such as theexclamation point and theat sign. The lack of anapostrophe led some software authors to use a comma instead.

There are 11block graphics characters, counting code point 0 which also doubles as space. The first 8 of these together with their 8 inverse video versions (16 code points) provide every combination of the character cell divided into 2×2 black-and-white block pixels for low-resolution 64×48 pixel graphics. These 2×2 blocks are present in theBlock ElementsUnicode block. An additional 3 characters provide a cell divided into 1×2 black, white ordithered gray wide block pixels. These, in combination with their inverse video versions and some of the previous 2×2 blocks provides for a 32×48 resolution with 3 levels (white, dithered gray, black). The basic 11 characters plus their inverse video versions, makes for 22block graphics characters in total. The dithered characters (of which there are 6) are also available in Unicode (mostly in theSymbols for Legacy Computing block), but only in Unicode versions 13.0 and newer, available from 2020 onwards.

Code point 11 is the double-quote (") symbol when used in the display file. The BASIC functionCHR$ 192 prints as the same character but is shown as "" in BASIC source listings; it is used for including the literal " character in a string without conflict with the " string delimiter.^[1]

The character set in the ZX81 was derived from theZX80 character set. They have mostly the same code points, e.g. for A-Z and 0-9, but the code points are different for the block graphics characters, the symbols ", -, +, *, /, =, >, <, and the BASIC keyword tokens (with many new added). There are also changes to the control characters. Code point 1 is no longer an unprintable string terminator. The ZX81 8K BASICROM was also available as an upgrade for the ZX80, replacing its integer-only 4K BASIC ROM.^[2]

The ZX81 system font uses an 8×8 pixel-per-character grid where most glyphs fit in 6×6 pixels leaving two pixels horizontal and vertical space between rows and columns. The ZX80's ROM which had slightly wider 7×6 pixel glyphs with only one pixel horizontal space between them. Some glyphs also received a different design in the ZX81 system font, noticeable on the *, the slashed and less rounded 0, and the less rounded $, C, G and J.

In the laterZX Spectrum the entire character encoding was replaced with theZX Spectrum character set, which is a derivative of ASCII and includes lower case letters and more.

The following table shows the ZX81 character set. Each character is shown with a potentialUnicode equivalent. Space and control characters are represented by the abbreviations for their names.

ZX81 character set^[1][3]

0

1

2

3

4

5

6

7

8

9

A

B

C

D

E

F

0x

SP

"[a]

£

$

:

?

1x

(

)

>

<

=

+

-

*

/

;

,

.

0

1

2

3

2x

4

5

6

7

8

9

A

B

C

D

E

F

G

H

I

J

3x

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

4x

RND

INKEY$

PI

5x

6x

7x

UP

DOWN

LEFT

RIGHT

graphics

EDIT

newline

rubout

K/L MODE

function

number

cursor

8x

"

£

$

:

?

9x

(

)

>

<

=

+

-

*

/

;

,

.

0

1

2

3

Ax

4

5

6

7

8

9

A

B

C

D

E

F

G

H

I

J

Bx

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

Cx

""[a]

AT

TAB

CODE

VAL

LEN

SIN

COS

TAN

ASN

ACS

ATN

LN

EXP

INT

Dx

SQR

SGN

ABS

PEEK

USR

STR$

CHR$

NOT

**[b]

OR

AND

<=[c]

>=[d]

<>[e]

THEN

TO

Ex

STEP

LPRINT

LLIST

STOP

SLOW

FAST

NEW

SCROLL

CONT

DIM

REM

FOR

GOTO

GOSUB

INPUT

LOAD

Fx

LIST

LET

PAUSE

NEXT

POKE

PRINT

PLOT

RUN

SAVE

RAND

IF

CLS

UNPLOT

CLEAR

RETURN

COPY

Sinclair BASICtokenizes keywords into single-byte code points.

• ZX80 character set
• ZX Spectrum character set
• Sinclair QL character set
• ATASCII
• Atari ST character set
• PETSCII
• Extended ASCII

• Character sets
• ZX81

• Articles with short description
• Short description is different from Wikidata