Type-in program

Type-ins existed because of the early home computer era's absence of inexpensive portable storage media for inclusion in books or magazines, as well as the relatively short length needed for an instructive and/or entertaining program for computers with main memories of only a few (tens of) kilobytes.

As the cost of cassette tapess and floppy disks declined, the importance of the type-in also declined. In Europe, cover tapes and later, disks, became common, and type-ins became virtually non-existent. The situation was different in North America, where they remained popular for 8 bit computers well into the 1990s, although type-ins for 16 bit and 32 bit computers quickly faded. U.S.-based magazines took advantage of the falling price of disks by offering their type-ins on disk, often with a bonus program or two, at a higher price.

Magazines on both continents continued to sometimes print short code snippets for instruction purposes, but these short 10–20 lines wouldn't be considered type-in programs in the proper sense.

Type-ins were usually written in BASIC or a combination of BASIC and machine language. In the latter case, the opcodes and operands of the machine language part were often simply given as DATA statements within the BASIC program, and which were loaded using a POKE loop (few users had access to an assembler). In some cases, a special program for entering machine language as more compact hexadecimal code was provided.

The downside of large machine code programs published as DATA statements inside a BASIC wrapper program was that the resulting listing was very long and utterly boring, with nothing but impersonal numbers repeating over and over again. This made actually typing the programs in a very laborous task. An example of this is a BASIC extension for the Commodore 64 published in the Finnish magazine MikroBITTI, whose machine code portion spanned over 20 pages.

Because code entry was prone to typing errors, some U.S. and European magazines developed checksum programs, which flashed a two or three character checksum in the corner of the screen every time a user entered a line. The checksum could then be compared to the checksums in the listing, and corrected if a mismatch occurred.

Books and leaflets featuring type-in programs, sometimes specific to a given home computer and sometimes compatible with several computers, were common. Although such programs were usually copyrighted, users were encouraged to modify them, adding capabilities or otherwise changing them to suit their needs—an early form of open source software.

While most type-ins were simple games or utilities and only held a user's interest for a short time, some type-ins were very ambitious, rivaling commercial software. Perhaps the most famous example is the type-in word processor SpeedScript, published by Compute magazine for several computers starting in 1984. It retained a following into the next decade as users refined and added capabilities to it.

Although type-in programs have disappeared today, the tradition of distributing software with magazines lived on, especially in Europe, with 3½" floppy disks included with magazines throughout most of the 1990s, eventually followed by CD-ROMs and DVDs.