Appendix 1 — Numbers, Notation, and ASCII

This appendix collects the number and character tables you reach for often in Z80 work.

Number Prefixes Used In This Course

Form Meaning Example
42 decimal 42
$2A hexadecimal $2A
%00101010 binary %00101010
0b00101010 binary (alternate form accepted by AZM) 0b00101010

Hex Digit Table

Hex Binary Decimal
0 0000 0
1 0001 1
2 0010 2
3 0011 3
4 0100 4
5 0101 5
6 0110 6
7 0111 7
8 1000 8
9 1001 9
A 1010 10
B 1011 11
C 1100 12
D 1101 13
E 1110 14
F 1111 15

Common Hex Landmarks

Value Decimal Why it matters
$00 0 zero byte
$0F 15 low nibble all set
$10 16 one hex digit boundary
$1F 31 5-bit max unsigned
$20 32 ASCII space
$7F 127 7-bit signed max / ASCII top
$80 128 sign bit set
$FF 255 byte all set / -1 in two’s complement
$0100 256 common code base in this course
$7FFF 32767 signed 16-bit positive max
$8000 32768 high bit set in a word / common RAM base in examples
$FFFF 65535 word all set / -1 as 16-bit two’s complement

7-bit ASCII (0–127)

Dec Hex Character Meaning
0 $00 NUL control code
1 $01 SOH control code
2 $02 STX control code
3 $03 ETX control code
4 $04 EOT control code
5 $05 ENQ control code
6 $06 ACK control code
7 $07 BEL control code
8 $08 BS control code
9 $09 TAB control code
10 $0A LF control code
11 $0B VT control code
12 $0C FF control code
13 $0D CR control code
14 $0E SO control code
15 $0F SI control code
16 $10 DLE control code
17 $11 DC1 control code
18 $12 DC2 control code
19 $13 DC3 control code
20 $14 DC4 control code
21 $15 NAK control code
22 $16 SYN control code
23 $17 ETB control code
24 $18 CAN control code
25 $19 EM control code
26 $1A SUB control code
27 $1B ESC control code
28 $1C FS control code
29 $1D GS control code
30 $1E RS control code
31 $1F US control code
32 $20 space printable
33 $21 ! printable
34 $22 " printable
35 $23 # printable
36 $24 $ printable
37 $25 % printable
38 $26 & printable
39 $27 ' printable
40 $28 ( printable
41 $29 ) printable
42 $2A * printable
43 $2B + printable
44 $2C , printable
45 $2D - printable
46 $2E . printable
47 $2F / printable
48 $30 0 printable
49 $31 1 printable
50 $32 2 printable
51 $33 3 printable
52 $34 4 printable
53 $35 5 printable
54 $36 6 printable
55 $37 7 printable
56 $38 8 printable
57 $39 9 printable
58 $3A : printable
59 $3B ; printable
60 $3C < printable
61 $3D = printable
62 $3E > printable
63 $3F ? printable
64 $40 @ printable
65 $41 A printable
66 $42 B printable
67 $43 C printable
68 $44 D printable
69 $45 E printable
70 $46 F printable
71 $47 G printable
72 $48 H printable
73 $49 I printable
74 $4A J printable
75 $4B K printable
76 $4C L printable
77 $4D M printable
78 $4E N printable
79 $4F O printable
80 $50 P printable
81 $51 Q printable
82 $52 R printable
83 $53 S printable
84 $54 T printable
85 $55 U printable
86 $56 V printable
87 $57 W printable
88 $58 X printable
89 $59 Y printable
90 $5A Z printable
91 $5B [ printable
92 $5C \\ printable
93 $5D ] printable
94 $5E ^ printable
95 $5F _ printable
96 $60 ` printable
97 $61 a printable
98 $62 b printable
99 $63 c printable
100 $64 d printable
101 $65 e printable
102 $66 f printable
103 $67 g printable
104 $68 h printable
105 $69 i printable
106 $6A j printable
107 $6B k printable
108 $6C l printable
109 $6D m printable
110 $6E n printable
111 $6F o printable
112 $70 p printable
113 $71 q printable
114 $72 r printable
115 $73 s printable
116 $74 t printable
117 $75 u printable
118 $76 v printable
119 $77 w printable
120 $78 x printable
121 $79 y printable
122 $7A z printable
123 $7B { printable
124 $7C \| printable
125 $7D } printable
126 $7E ~ printable
127 $7F DEL control code