Classic Computer Magazine Archive COMPUTE! ISSUE 55 / DECEMBER 1984 / PAGE 10

Commodore Tape Sequential Access

I own a VIC-20 and have found that the computer won't recognize a file unless the cassette is set near the beginning of the file. Can this limitation be resolved?

Andy Little

Cassette files are always sequential, and must be read in the same order that they were written. The first part of a tape file is a header containing the filename and other information such as the starting and ending address of a program. Without this header, the computer's Kernal tape routines do not know how to locate and use the data that follows, so you can't just start reading a cassette file partway through. There are ROM routines for directly reading and writing blocks of data to the tape, but the technique is too involved to cover here, and there are many problems with such a method.