true ......................................... 71,72
two-dimensional array ............................ 68
TZX files ....................................... 156

U
UART ............................................ 155
UDG ......................................... 49,75,128
ULA ............................................. 103
unary ! .......................................... 48
unary not ........................................ 46
Unary/Bitwise NOT (!) ............................ 38
unified sprite ............................... 137,138
Unsigned .................................... 45,46,47,48
unsigned expression .............................. 48
user-defined graphic ............................. 76
user-defined graphics ............................ 75
Using Expressions for INPUT ...................... 91
USR ......................................... 59,75,76

VAL ..................................... 51,52,55,124
VAL$ ......................................... 51,55
Variable names ................................... 39
Variable not found ............................... 92
vertical size .................................... 96
visibility ...................................... 136
Visibility flag ................................. 136
Volume effects .................................. 151

W
WAIT ....................................... 140,141
WAV ............................................. 154
WHILE ............................................ 25
WRITE ........................................... 142

X
XOR .............................................. 45