The Kansas City standard (KCS), or ''Byte'' standard, is a data storage protocol for standard

cassette tape The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. Invented by Lou Ottens ...

s at . It originated in a symposium sponsored by ''Byte'' magazine in November 1975 in

Kansas City, Missouri Kansas City (abbreviated KC or KCMO) is the largest city in Missouri by population and area. As of the 2020 census, the city had a population of 508,090 in 2020, making it the 36th most-populous city in the United States. It is the central ...

to develop a standard for the storage of digital

microcomputer A microcomputer is a small, relatively inexpensive computer having a central processing unit (CPU) made out of a microprocessor. The computer also includes memory and input/output (I/O) circuitry together mounted on a printed circuit board (PC ...

data on inexpensive consumer quality cassettes. The first systems based on the standard appeared in 1976. One variation on the basic standard is CUTS, which is identical at 300 bit/s, but with an optional 1200 bit/s mode. CUTS is the default encoding used by several later machine families, including those from

Acorn The acorn, or oaknut, is the nut of the oaks and their close relatives (genera ''Quercus'' and '' Lithocarpus'', in the family Fagaceae). It usually contains one seed (occasionally two seeds), enclosed in a tough, leathery shell, and borne ...

and the MSX. MSX added a higher 2400 bit/s mode that is otherwise similar. The 1200 bit/s mode of CUTS was used as the standard for cross-platform

BASICODE BASICODE was a computer project intended to create a unified standard for the BASIC programming language. BASIC was available on many popular home computers, but there were countless variants that were mostly computer compatibility, incompatible w ...

distribution. KCS originated from the earliest days of the microcomputer revolution, among other prolific protocols. Most home computers of the era have unique formats that are incompatible with anything.

History

Early microcomputers generally use

punched tape Five- and eight-hole punched paper tape Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated paper tape is a form of data storage ...

for program storage, an expensive option. Computer consultant Jerry Ogdin conceived the use of audio tones on a cassette to replace the paper tapes. He took the idea to Les Solomon, editor of ''

Popular Electronics ''Popular Electronics'' was an American magazine published by John August Media, LLC, and hosted at TechnicaCuriosa.com. The magazine was started by Ziff-Davis Publishing Company in October 1954 for electronics hobbyists and experimenters. It soo ...

'' magazine, who was similarly frustrated by punched tapes. In September 1975, the two co-authored an article on the HITS (Hobbyists' Interchange Tape System), using two tones to represent 1s and 0s. Soon after, several manufacturers started using similar approaches, all incompatible.Les Solomon
"Solomon's Memory"
Digital Deli, 1984

Wayne Green Wayne Sanger Green II (September 3, 1922 – September 13, 2013) was an American publisher, writer, and consultant. Green was editor of '' CQ'' magazine before he went on to found '' 73'', ''80 Micro'', ''Byte'', '' CD Review'', ''Cold Fusion'', ...

, who had just started ''Byte'' magazine, wanted all the manufacturers to collaborate on a single cassette standard. He organized a two-day meeting on 7–8 November 1975 in

. The participants settled on a system based on

Don Lancaster Donald E. Lancaster is an American author, inventor, and microcomputer pioneer. Background Lancaster is a writer and engineer, who authored multiple articles for computer and electronics magazines of the 1970s, including ''Popular Electronics' ...

's design. After the meeting,

Lee Felsenstein Lee Felsenstein (born April 27, 1945) is an American computer engineer who played a central role in the development of the personal computer. He was one of the original members of the Homebrew Computer Club and the designer of the Osborne 1, the ...

(of

Processor Technology Processor Technology Corporation was a personal computer company founded in April 1975 by Gary Ingram and Bob Marsh in Berkeley, California. Their first product was a 4K byte RAM board that was compatible with the MITS Altair 8800 computer but mo ...

) and Harold Mauch (of

Percom Percom Data was an early microcomputer company formed in 1976 to sell peripherals into the emerging microcomputer market. They are best known for their floppy disk systems, first for S-100 machines, and the later for other platforms like the TRS-8 ...

) wrote the standard, which was published in ''Byte'' magazine's first issue. A KCS cassette interface is similar to a modem connected to a

serial port In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. ...

. The 1s and 0s from the serial port are converted to audio tones using audio

frequency-shift keying Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier signal. The technology is used for communication systems such as telemetry, weather ball ...

(AFSK). A "0" bit is represented as four cycles of a 1200 Hz

sine wave A sine wave, sinusoidal wave, or just sinusoid is a curve, mathematical curve defined in terms of the ''sine'' trigonometric function, of which it is the graph of a function, graph. It is a type of continuous wave and also a Smoothness, smooth p ...

, and a "1" bit as eight cycles of 2400 Hz. This gives a data rate of 300

baud In telecommunication and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel. It is the unit for symbol rate or modulatio ...

. Each frame starts with one "0" start bit, followed by eight data bits (least significant bit first) followed by two "1" stop bits, so each frame is 11 bits, for a data rate of bytes per second. The February 1976 issue of ''Byte'' has a report on the symposium, and the March issue features two hardware examples by Don Lancaster and Harold Mauch. The 300 baud rate is reliable, but slow; a typical 8-kilobyte

BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...

program takes five minutes to load. Most audio cassette circuits support higher speeds. According to Solomon, the efforts were unsuccessful: "Unfortunately, it didn't last long; before the month ended, everyone went back to his own tape standard and the recording confusion got worse." The participants of the Kansas City symposium include these: *

Ray Borrill Boyd Raymond 'Ray' Borrill was founder of The Data Domain, a retail computer store in Bloomington, Indiana, and vice-president of itty bitty machine company retail computer store, December 1975 – 1980, located in Evanston, Illinois. These stor ...

, Bloomington, Indiana *

Hal Chamberlin Howard Allen Chamberlin, Jr. is an American audio engineer and writer from North Carolina, most widely known as the author of the book ''Musical Applications of Microprocessors''. Biography In the 1970s while still at school he built an analog ...

, The Computer Hobbyist, Raleigh, North Carolina * Richard Smith, The Computer Hobbyist, Raleigh, North Carolina * Tom Durston, MITS, Albuquerque, New Mexico *

Bill Gates William Henry Gates III (born October 28, 1955) is an American business magnate and philanthropist. He is a co-founder of Microsoft, along with his late childhood friend Paul Allen. During his career at Microsoft, Gates held the positions ...

, MITS, Albuquerque, New Mexico * Ed Roberts, MITS, Albuquerque, New Mexico * Bob Zaller, MITS, Albuquerque, New Mexico *

, LGC Engineering /

, Berkeley, California * Les Solomon,

Magazine, New York, New York * Bob Marsh,

, Berkeley, California * Joe Frappier, Mikra-D, Bellingham, Massachusetts * Gary Kay, Southwest Technical Products Corp, San Antonio, Texas * Harold A Mauch, Pronetics/Percom Data, Garland Texas * Bob Nelson, PCM, San Ramon, California * George Perrine, HAL Communications Corp, Urbana, Illinois * Paul Tucker, HAL Communications Corp, Urbana, Illinois * Michael Stolowitz, Godbout Electronics, Oakland, California * Mike Wise, Sphere, Bountiful, Utah

Enhancements

The original standard records data as "marks" (one) and "spaces" (zero). A mark bit consists of eight cycles at a frequency of 2400 Hz, and a space bit consists of four cycles at a frequency of 1200 Hz. A

word A word is a basic element of language that carries an semantics, objective or pragmatics, practical semantics, meaning, can be used on its own, and is uninterruptible. Despite the fact that language speakers often have an intuitive grasp of w ...

, usually one

byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...

(8 bits) long, is recorded in

little endian In computing, endianness, also known as byte sex, is the order or sequence of bytes of a word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the most sig ...

order, which is least significant bit first. 7-bit words are followed by a

parity bit A parity bit, or check bit, is a bit added to a string of binary code. Parity bits are a simple form of error detecting code. Parity bits are generally applied to the smallest units of a communication protocol, typically 8-bit octets (bytes) ...

developed the popular CUTS (Computer Users' Tape Standard), which works at either 300 or 1200 baud. They provided the

S-100 bus The S-100 bus or Altair bus, IEEE 696-1983 ''(withdrawn)'', is an early computer bus designed in 1974 as a part of the Altair 8800. The bus was the first industry standard expansion bus for the microcomputer industry. computers, consisting of ...

CUTS Tape I/O interface board, which offers both CUTS and Kansas City standard support to any S-100 system. The

Tarbell Cassette Interface The Tarbell Cassette Interface is an expansion card for use with the Altair 8800 early personal computer, or other systems using the Altair's S-100 bus. It was designed by Don Tarbell and sold by Tarbell Electronics as early as 1976. At the time, ...

, which, according to early PC retailer Stan Veit, "became a ''de facto'' standard for S-100 computers", supported the Kansas City Standard in addition to the Tarbell "native" mode ("Tarbell standard").

Acorn Computers Ltd The acorn, or oaknut, is the nut of the oaks and their close relatives (genera ''Quercus'' and ''Lithocarpus'', in the family Fagaceae). It usually contains one seed (occasionally two seeds), enclosed in a tough, leathery shell, and borne i ...

implemented a 1200-baud variation of ''CUTS'' in its

BBC Micro The British Broadcasting Corporation Microcomputer System, or BBC Micro, is a series of microcomputers and associated peripherals designed and built by Acorn Computers in the 1980s for the BBC Computer Literacy Project. Designed with an emphas ...

and

Acorn Electron The Acorn Electron (nicknamed the Elk inside Acorn and beyond) was a lower-cost alternative to the BBC Micro educational/ home computer, also developed by Acorn Computers Ltd, to provide many of the features of that more expensive machine at a ...

microcomputers, which reduced a "0" bit to one cycle of a 1200 Hz sine wave and a "1" bit to two cycles of a 2400 Hz wave. Standard encoding includes a "0" start bit and "1" stop bit around every 8 bit piece of information, giving an effective data rate of 960

bits per second In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction w ...

. Also, these machines record data in 256-byte blocks interspersed with gaps of carrier tone, each block carrying a sequence number and a CRC checksum, so that it is possible to rewind the tape and retry from the failed block when a read error occurs. The MSX by default supports both a 1200 baud variation of the standard with the same bit encoding as Acorn's, and a 2400 baud variant which doubles the audio rate — a "0" bit is one cycle of a 2400 Hz wave and a "1" bit is two cycles of a 4800 Hz wave. Unlike Acorn machines, the MSX uses two "1" stop bits in addition to one "0" start bit, so the effective rate at 1200 baud is approximately 873 bits per second, and the effective rate at 2400 baud is approximately 1,745 bits per second. The machine's BIOS can read data at up to 3600 baud from an ideal audio source. The Quick CUTS standard proposed by Bob Cottis and Mike Blandford and published in the Amateur Computer Club newsletter also operated at 2400 baud, encoding "0" as a half-cycle of 1200 Hz and "1" as a whole cycle of 2400 Hz. The receiver was self-clocking using a

phase-locked loop A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal. There are several different types; the simplest is an electronic circuit consisting of a ...

. Published in 1978, it predates the 1982 patent for the similar

coded mark inversion frame, CMI line coding In telecommunication, coded mark inversion (CMI) is a non-return-to-zero (NRZ) line code. It encodes ''zero'' bits as a half bit time of zero followed by a half bit time of one, and while ''one'' bits are encoded as a full b ...

proposal.

Implementations

Early microcomputers

Several use the S-100 bus. *

Compukit UK101 The Compukit UK101 microcomputer (1979) is a kit clone of the Ohio Scientific Superboard II single-board computer, with a few enhancements for the UK market - notably replacing the 24×24 (add guardband kit to give 32×32) screen display with a ...

Exidy Sorcerer The Sorcerer is a home computer system released in 1978 by the video game company Exidy. Based on the Zilog Z80 and the general layout of the emerging S-100 standard, the Sorcerer was comparatively advanced when released, especially when compar ...

Optional S-100 expansion bus, standard 300 bit/s mode and a 1200 baud variant by default. *Kim-1, MOS Technology Optional S-100 expansion bus (KIMSI), standard 300 bit/s mode and a hypertype 1200 baud variant. * Lucas Nascom 1, 2 (which also supports a 1200 bit/s variant, see below) * MITS

Altair 8800 The Altair 8800 is a microcomputer designed in 1974 by MITS and based on the Intel 8080 CPU. Interest grew quickly after it was featured on the cover of the January 1975 issue of Popular Electronics and was sold by mail order through advertiseme ...

Motorola Motorola, Inc. () was an American Multinational corporation, multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent p ...

MEK D1 6800 board *

Ohio Scientific Ohio Scientific Inc. (also known as Ohio Scientific Instruments) was an Ohio-based computer company that built and marketed microcomputers from 1975 to 1981. Their best-known products were the Challenger series of microcomputers and Superboard si ...

C1P/ Superboard II * Processor Tech

Sol-20 The Sol-20 was the first fully assembled microcomputer with a built-in keyboard and television output, what would later be known as a home computer. The design was a combination of an Intel 8080-based motherboard, a VDM-1 graphics card, the 3P+S ...

Terminal Computer *Processor Tech CUTS S-100 bus Tape I/O interface board *

SWTPC Southwest Technical Products Corporation, or SWTPC, was an American producer of electronic kits, and later complete computer systems. It was incorporated in 1967 in San Antonio, Texas, succeeding the Daniel E. Meyer Company. In 1990, SWTPC beca ...

Motorola 6800 The 6800 ("''sixty-eight hundred''") is an 8-bit computing, 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the Motorola 6800 family, M6800 Microcomputer System (latter dubbed ''68xx' ...

-based computers *

Tangerine Microtan 65 The Tangerine Computer Systems, Tangerine Microtan 65 (sometimes abbreviated M65) was a MOS Technology 6502, 6502 based single board microcomputer, first sold in 1979, which could be expanded into, what was for its day, a comprehensive and powerfu ...

(300 baud CUTS — faster 2400 non-CUTS format also available) *Eltec (German Company) Eurocom 1 *Z80 Starter Kit (1977 — Development board by SD Systems — 300 bauds — S-100 bus)

Personal computers

ABC 80 The ABC 80 (Advanced BASIC Computer 80) was a personal computer engineered by the Swedish corporation Dataindustrier AB (DIAB) and manufactured by Luxor in Motala, Sweden in the late 1970s and early 1980s. It was introduced on the market in August ...

Acorn System 1 The Acorn System 1, initially called the Acorn Microcomputer (Micro-Computer), was an early 8-bit microcomputer for hobbyists, based on the MOS 6502 CPU, and produced by British company Acorn Computers from 1979. The main parts of the system ...

(300 baud only) **

Acorn Atom The Acorn Atom is a home computer made by Acorn Computers Ltd from 1980 to 1982, when it was replaced by the BBC Micro. The Micro began life as an upgrade to the Atom, originally known as the Proton. The Atom was a progression of the MOS Techn ...

(300 baud standard / 1200 baud with the "fast cos" program from utility pack 1) **

(300 and 1200 baud variations) **

(1200 baud only) * Dick Smith Super-80 (300 baud only) *

Elektor :''Elektor (ἠλέκτωρ) is also an ancient Greek name or epithet of the Sun, see Helios.'' ''Elektor'', also known as ''Elektor Magazine'', is a monthly magazine about all aspects of electronics, originally published in the Netherlands as ...

Magazine National SC/MP Project *

Heathkit Heathkit is the brand name of kits and other electronic products produced and marketed by the Heath Company. The products over the decades have included electronic test equipment, high fidelity home audio equipment, television receivers, amateu ...

**Heathkit ET/ETW-3400 and 3400A Microprocessor Trainers (300, 1200, 2400 baud) **

Heathkit H8 Heathkit's H8 is an Intel 8080A-based microcomputer sold in kit form starting in 1977. The H8 is similar to the S-100 bus computers of the era, and like those machines is often used with the CP/M operating system on floppy disk. The main diffe ...

(300 and 1200 baud) **

Zenith Z-89 The Z-89 is a personal computer produced by Zenith Data Systems (ZDS) in the early 1980s. Description The Zenith Z-89 is based on the Zilog Z80 microprocessor running at 2.048 MHz, and supports the HDOS and CP/M operating systems. The ...

— also sold as the Heathkit H89 (300 and 1200 baud) * MicroBee Systems ** MicroBee (300 and 1200 baud) * MSX (1200 and 2400 baud) *

Nascom The Nascom 1 and 2 were single-board computer kits issued in the United Kingdom in 1977 and 1979, respectively, based on the Zilog Z80 and including a keyboard and video interface, a serial port that could be used to store data on a tape cassette ...

(300 and 1200) * Sega SC-3000 A slightly different 600 baud variant *Triumph-Adler **Alphatronic PC **Alphatronic PC16 * Z80NE Nuova Elettronica with LX.385 interface
Chaos Homebrew Computer

Programmable calculators

Casio is a Japanese multinational electronics manufacturing corporation headquartered in Shibuya, Tokyo, Japan. Its products include calculators, mobile phones, digital cameras, electronic musical instruments, and analogue and digital watches. It ...

** FX-502P series with FA-1 interface (300 baud) ** FX-602P series and FX-702P with FA-2 interface (300 baud) ** Casio FX-603P and

Casio FX-850P The Casio FX-850P is a scientific calculator introduced in 1987 and sold until 1999. Specifications * 2 lines with 32 5×7 characters LCD ** (some indicators and a 5 digit 7-segment display) * 8 KB RAM (FX-860P: 24 KB, FX-880P: 32 KB) * CPU: V ...

with FA-6 interface (300 and 1200 baud) **Casio FX-750P with FA-20 interface (300 baud) **Casio PB-700 with FA-11 interface (300 baud)

Other devices

* Casio PT-50

electronic keyboard An electronic keyboard, portable keyboard, or digital keyboard is an electronic musical instrument, an electronic derivative of keyboard instruments. Electronic keyboards include synthesizers, digital pianos, stage pianos, electronic organs an ...

with TA-1 tape interface module. *

Roland TR-707 The Roland TR-707 Rhythm Composer is a drum machine released by the Roland Corporation in 1985. Features The TR-707 has fifteen digitally sampled sounds. The instrument is capable of 10-voice polyphony. The alternate bass drum, snare, and hi- ...

drum machine and other musical equipment.

Alternative formats

In August 1976 at the Personal Computing show in

Atlantic City, New Jersey Atlantic City, often known by its initials A.C., is a coastal resort city in Atlantic County, New Jersey, United States. The city is known for its casinos, boardwalk, and beaches. In 2020, the city had a population of 38,497.

, Bob Marsh of Processor Technology approached Bob Jones, the publisher of ''

Interface Age ''Interface Age'', "published for the home computerist", was a computer magazine aimed at the early microcomputer and home computer market. Its first issue was published in August 1976 and the last one in September 1984. It had a technical focus ...

'' magazine, about pressing software onto vinyl records. Processor Technology provided an

Intel 8080 The Intel 8080 (''"eighty-eighty"'') is the second 8-bit microprocessor designed and manufactured by Intel. It first appeared in April 1974 and is an extended and enhanced variant of the earlier 8008 design, although without binary compatibil ...

program to be recorded. This test record did not work and Processor Technology was unable to devote more time to the effort. Daniel Meyer and Gary Kay of Southwest Technical Products (SWTPC) arranged for Robert Uiterwyk to provide his 4K BASIC interpreter program for the

microprocessor. The idea was to record the program on audio tape in the Kansas City format and then make a master record from the tape. Eva-Tone made Soundsheets on thin vinyl that would hold one song, these were inexpensive and could be bound in a magazine. Bill Turner and Bill Blomgren of MicroComputerSystems Inc. along with Bob Jones^{/sup> of ''Interface Age'' and Bud Schamburger of Holiday Inn worked with Eva-Tone and developed a successful process. The intermediate stage of recording to tape produced dropouts, so a SWTPC AC-30 cassette interface was connected directly to the record cutting equipment. The May 1977 issue of ''Interface Age'' contains the first "Floppy ROM", a 33 RPM record containing about six minutes of Kansas City standard audio. The September 1978 Floppy ROM Number 5 has two sides: Apple BASIC, "the automated dress pattern", and IAPS format, "A program for writing letters".

See also

* BASICODE

BASICODE was a computer project intended to create a unified standard for the BASIC programming language. BASIC was available on many popular home computers, but there were countless variants that were mostly computer compatibility, incompatible w ...

* Commodore Datasette
The third, most common version of the 1530 C2N Datassette

The Commodore 1530 (C2N) Datasette, later also Datassette (a portmanteau of ''data'' and ''cassette''), is Commodore's dedicated magnetic tape data storage device. Using compact cassettes ...

* Fast loader

A fast loader is a software program for a home computer, such as the Commodore 64 or ZX Spectrum, that accelerates the speed of file loading from floppy disk or compact cassette.
Floppy disks
Fast loaders came about because of a discrep ...

* Flexi disc

The flexi disc (also known as a phonosheet, Sonosheet or Soundsheet, a trademark) is a phonograph record made of a thin, flexible vinyl sheet with a molded-in spiral stylus groove, and is designed to be playable on a normal phonograph turntable. ...

* IBM cassette tape The original IBM Personal Computer and IBM PCjr included support for storing data and programs on compact cassette tape.

It was common for home computers of the time, such as the Apple II, Commodore 64 and BBC Micro, to use cassette tapes for sto ...

* Tarbell Cassette Interface

The Tarbell Cassette Interface is an expansion card for use with the Altair 8800 early personal computer, or other systems using the Altair's S-100 bus. It was designed by Don Tarbell and sold by Tarbell Electronics as early as 1976. At the time, ...

* Unified Emulator Format

Further reading

*
*
*

References

External links

The original Byte Magazine article

2-second sound sample of stored KCS file

Percom Data CIS-30 Cassette Interface Brochure

Kansas City Tape Decoder

Kansas City Tape Decoder (Modern win32 version)

{{magnetic tape data formats

Computer standards
Early microcomputers
Tape-based computer storage
Standards of the United States}