Commodore VIC-20 - Page 400

386 The VIC 20 User Guide
Datasette (continued)
connecting. 21
loading programs from cassette, 47
reading data from, 257-59
saving programs on cassette, 46
testing,
22
verifying that a program was saved, 47
writing data on, 255-57
DEF FN statement,
115, 344
device numbers, 254
DIM (dimension) statement, 88,
345
Disk drive
BAM,262
BLOCK-ALLOCATE instruction, 272
BLOCK-FREE instruction, 275
BLOCK-READ instruction, 269
BLOCK-WRITE instruction, 273
BUFFER-POINTER instruction, 274
concatenating files on, 265
connecting, 27
connecting more than one, 265-66
copying files on,
265
directory, 262
erasing files on, 264
formatting a diskette, 51, 263
how data are stored on, 260
indicator lights, 28
loading and unloading diskettes, 28, 30
loading programs from,
47
MEMORY-EXECUTE instruction, 279
MEMORY-READ instruction, 278
MEMORY-WRITE instruction,
277
number of files allowed, 250
operating, 49-54
reading data from, 257-59
renaming files on, 264
saving programs on, 46
testing,
27
user (Un) commands, 279-80
utility instructions, 269-80
VALIDATE command, 264
writing data on, 268
Diskettes. See Floppy disks
E
END statement, 110, 345
ERROR messages, 335-40
EXP function, 113, 373
F
fields, 251
Files
buffers, 252
copying disk files, 265
data files, 25 I
Datasette, 254-60
Files
(continued)
defined, 250
erasing disk files, 264
fields, defined, 251
file numbers, 252
limits
on number of open files, 268
naming rules, 250
PRINT# statement, 268
program files, 250
random access files,
268
records, defined, 251
renaming disk files, 264
sequential files, 266
Floppy disks. See also Disk drive
care, 31
sector, 262
selection, 29
write-protection, 31
FOR statement, 92, 346
FRE function, 115, 373
Function keys (FI, Fl, ... FS), 19-20
Functions
arithmetic, 112-13
defined, III
string, 114
system, 114-15
trigonometric, deriving those not supplied,
324
user-defined,
115
G
Game controllers. See Joystick controller,
Paddle controller
GET statement, 108-09, 133, 164-69, 347
"echoing" input keystrokes,
166
simulating a joystick (example), 166-69
using CHRS to check for "special"
characters, 129
GET# statement, 258, 271, 348
GOSUB statement, 98, 348. See also Computed
GOSUB
GOTO statement, 88, 349. See also Computed
GOTO
H
High-resolution graphics
defined,
208
programming techniques, 210-14
IF-THEN statement, 100,349
Immediate mode, 39
INITIALIZE (disk instruction), 51, 262, 350
INPUT statement, 106-08, 351
INPUT# statement, 258, 268, 352
INST/DEL (insert/delete) key, 19,41,42
INT function, 112, 374