Commodore PET User Manual page 95

File Input/Output: OPEN, CLOSE, PRINT#, CMD, INPUT#, GET#
File input/output statements provide programmed communication with the
cassette tape unit or any other external peripheral unit that can input and/or out-
put data.
OPEN assigns an identifier. called a logical file number, to a physical device
and readies the physical device for an input/output operation. Physical devices
have preassigned numbers. Logical file numbers are made up by the programmer.
just as variable names are.
11' : :1 OPEH 5,1 .• 0,"DATAFILE"
Assignslogicalunit5tophysicaldevicel
(the console cassette unit) and opens the
cassette for read (code 0) fram file name
DATAFILE.
CLOSE is executed when ail accesses to the logical file have been com-
pleted.
51'::10 CLOSE 5
Close logical file 5.
PRINT# operates essentially like PRINT but outputs to an external device.
40 F'RINT#2: .• A
Output the value of variable A to logical file 3.
CMD opens communication with an external device so that vou can print to
an external device what is normally displayed on the screen.
41' : :1 Ct1D 3
Output subsequent log to logical file 3.
INPUT# operates somewhat like READ, but it inputs data from an external
file rather than from DATA statements in the program. as READ does.
50 IHPUT#10 .. A
Input and assign to variable A the next data
item from logical file la.
GET# allows vou to fetch external data one character at a time.
6(1
GET#?. C$
Input and assign to variable C$ the next data
item from logical file 7.
None of these statements is used alone in a program; rather. successful in-
put or output to an external device requires a certain sequence of file input/output
statements. ail having compatible parameters, that together provide an input or
output capability. The format of these statements is described in Chapter 4. Using
these statements to perform file 1/0 operations is described further in Chapter 5.
File Input/Output.
Miscellaneous: REM, POKE
REM is a remark, or comment line. Remarks should be used frequently in a
program to remind the programmer what is happening.
10 REM FETCH DATA IF BUFFER EMPTY
82