Commodore 1551 User Manual page 6

PART TWO: GUIDE TO ADVANCED OPERATION AND PROGRAMMING 31
CHAPTER 4: SEQUENTIAL DATA FILES ............................... 31
The concept of files ............................................ 31
Opening a file. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 32
Adding to a sequential file .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34
Writing file data: Print
# .......................................
35
Closing a file when you are done using it . . . . . . . . . . . . . . . . . . . . . . . . .. 37
Reading file data: Input # ...................................... 38
More about Input # (advanced users) ............................ 39
Numeric data storage on diskettes ................................
40
Reading file data: Get
# ........................................
41
CHAPTER 5: RELATIVE FILES ................•......................
44
The value of relative access .....................................
44
Files, records, and fields ........................................ 44
File limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 45
Creating a relative file .......................................... 45
Using relative files: Record
#
command ........................... 46
Completing relative file creation ................................. 48
Expanding a relative file. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 49
Writing relative file data ........................................ 50
Designing a relative record. . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . .. 50
Writing the record ....................•........................ 51
Reading a relative record. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 53
The value of index files (advanced users) .......................... 54
CHAPTER 6: DIRECT ACCESS COMMANDS ........................... 55
A tool for advanced users. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 55
Diskette organization .......................................... 55
Opening a data channel for direct access . . . . • . . . . . . . . . . . . . . . . . . . .. 55
Block-read ................................................... 56
Block-write. . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 57
The original Block-read and Block-write commands . . . . . . . . . . . . . . .. 58
The buffer pointer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59
Allocating blocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60
Freeing blocks ....••.......................................... 61
Using random files (advanced users) .............................. 62
CHAPTER 7: INTERNAL DISK COMMANDS .......•.........•.......... 63
1551 memory map .............•............................... 63
Memory-read ................................................. 64
Memory-write .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65
Memory-execute .........................................•.... 66
Block-execute ...•.........•................•.................. 67
User commands .••....................•....................... 68