| name | c64-tape |
| description | The Commodore 64 Datassette / cassette tape: device 1, LOAD/SAVE/VERIFY, how tape files are found (sequential, no random-access directory), the tape buffer, headers, and the PRESS PLAY/RECORD prompts. Use this skill WHEN a user asks "how do I load/save from tape", "LOAD with no name", "how do I list a tape directory", "what's on this cassette", "why does it say PRESS PLAY ON TAPE", "what is the tape buffer at $033C", "how do I write data files to tape", or mentions the Datassette, device 1, or .tap/.t64 files. Pairs with c64-io, c64-kernal, and c64-assembly. |
C64 Cassette Tape (Datassette)
The Datassette is serial device 1, and it's the default for LOAD/SAVE
when you give no device number. Tape is sequential magnetic storage: files sit
one after another along the tape and you reach a file by spooling past everything
before it. There is no in-place rewrite and no random-access directory — that
distinction drives almost everything below.
Loading, saving, verifying programs
LOAD : REM load the NEXT program on the tape (from current position)
LOAD "NAME" : REM search FORWARD for program "NAME", then load it
LOAD "NAME",1 : REM same, device 1 explicit
LOAD "",1,1 : REM first program on tape, loaded to its ORIGINAL address
SAVE "NAME" : REM save current BASIC program to tape
SAVE "NAME",1,2 : REM save and write an end-of-tape (EOT) marker after it
VERIFY "NAME" : REM compare the tape file against memory
LOAD with no name reads whatever program comes next from where the tape is
parked. LOAD"NAME" scans forward until it finds a header matching NAME.- The secondary address on LOAD works like disk:
,1,1 loads to the address the
program was saved from (for ML/data), versus the default relocate to BASIC
start. On SAVE, sa 2 appends an EOT marker so a later read stops cleanly.
- Prompts the KERNAL prints: PRESS PLAY ON TAPE (for read), PRESS RECORD &
PLAY ON TAPE (for write). On LOAD the screen blanks to the border color while
searching; on a hit it shows FOUND NAME, clears, and (after you press C=,
CTRL, ←, or SPACE — or it just continues) shows LOADING.
There is NO tape directory
A cassette has no catalog the way a disk does. LOAD"$",8 works on disk because
the drive's DOS builds a directory; the Datassette has no DOS and $ means
nothing on tape. So the honest answer to "list a tape directory" is: you can't,
not as a single listing. Practical alternatives the manuals describe:
- Use the tape counter + your own log. Note the counter value where each
file begins (the manuals assume you write down what's on each tape).
- Walk the headers. Each file is preceded by a header containing its name.
LOAD"NAME" searches these headers forward; repeatedly issuing LOAD (no
name) and watching each FOUND xxxx message lets you see file names one by
one as the tape advances. There's no way to jump backward to an earlier file
without rewinding.
- EOT markers (written with SAVE sa 2) tell a sequential read when to stop,
so you don't run off the end into
?DEVICE NOT PRESENT.
Because tape is sequential, the common workflow is: read the whole file into RAM,
process it, then rewrite the whole file — there's no editing in place.
Data files on tape
For your own data (not programs), use OPEN/PRINT#/INPUT#/GET#:
OPEN 1,1,0,"NAME" : REM sa 0 = read
OPEN 1,1,1,"NAME" : REM sa 1 = write
OPEN 1,1,2,"NAME" : REM sa 2 = write, and write an EOT marker on CLOSE
The secondary address picks the mode: 0 read, 1 write, 2 write-with-EOT.
Worked write/read pair (from the User's Guide):
10 OPEN 1,1,1,"DATA FILE" 20 OPEN 1,1,0,"DATA FILE"
20 INPUT "DATA";A$ 50 INPUT#1,A$
30 PRINT#1,A$ 60 PRINT A$
40 IF A$<>"STOP" THEN 20 70 IF A$<>"STOP" THEN 50
50 CLOSE 1 80 CLOSE 1
Separator pitfall: PRINT#1,A$,B$,C$ with commas adds 1–10 padding spaces
(like screen columns), and INPUT#1,A$,B$,C$ then reads all three into A$ because
there's no separator between them — only a RETURN after the last. Put a RETURN
(CHR$(13)) or comma between items: R$=",":PRINT#1,A$ R$ B$ R$ C$. Also,
GET# returns CHR$(0) as an empty string "", so ASC(A$) on it errors — use
A=ASC(A$+CHR$(0)). Read references/cassette-tape.md for the full DOG/CAT/TREE
illustration; check the reserved variable ST for tape markers / end of file.
The tape buffer
The cassette I/O buffer is $033C–$03FB (828–1019 decimal), 192 bytes. It holds
the header and a data block during tape operations. When you're not using tape it
is a favorite spot for short machine-language routines — but it will be
overwritten the moment any tape I/O runs. For loading/parking ML there, see
c64-assembly.
Cassette port pins (edge connector)
| Pin | Signal |
|---|
| A-1 | GND |
| B-2 | +5V |
| C-3 | CASSETTE MOTOR |
| D-4 | CASSETTE READ |
| E-5 | CASSETTE WRITE |
| F-6 | CASSETTE SENSE (PLAY/RECORD pressed) |
Quick answers
- "How do I list a tape directory?" You can't — tape has no directory. Use
the tape counter, your own written log, or step through with repeated
LOAD
(no name) watching each FOUND name message.
- "What does LOAD with no name do?" Loads the next program on the tape.
- "How do I save to tape?"
SAVE "NAME" (device 1 is the default).
- "Why PRESS PLAY ON TAPE?" The KERNAL is waiting on the SENSE line; press the
Datassette's PLAY (or RECORD+PLAY for writing).
- "Where's the tape buffer?" $033C–$03FB.
How to read the references
references/cassette-tape.md — verbatim PRG Ch6 "Working With Cassette
Tape" (the PRINT#/INPUT# separator problem with the DOG/CAT/TREE byte layout,
the GET#/CHR$(0) trap) plus the tape-relevant slices of the LOAD and OPEN
keyword entries (the FOUND/PRESS PLAY behavior, the sa 0/1/2 read/write/EOT
rules). Read this for the exact wording on file formatting and load behavior.references/advanced-cassette.md — verbatim User's Guide App B with the
complete write-to-tape and read-from-tape data-file programs and the GET#
variant. Read this for runnable data-file examples.
Cross-links
- The general device/file model (OPEN/PRINT#/INPUT#/GET#/CLOSE, device numbers,
secondary addresses) → c64-io
- KERNAL LOAD/SAVE/tape routines → c64-kernal
- Stashing machine-language code in the tape buffer at $033C → c64-assembly
