ASCII

The ASCII code was born in the 1960s, when every computer manufacturer was inventing its own rules. At that time, exchanging data between machines was an ordeal. A character on an IBM computer was unreadable on a Control Data machine, and vice versa. This technological cacophony hindered any serious development of computing.

In 1961, the American Standards Association decided to end this chaos. Its X3 committee received the mission to create a universal standard. The project landed in the hands of subcommittee X3.2, then working group X3.2.4. John L. Little, an engineer at the National Bureau of Standards, took charge of this delicate undertaking. He had to convince manufacturers who were already using their own systems, like Control Data with its 6-bit FIELDATA or IBM with its 8-bit EBCDIC. But each one held firm to their positions.

After months of debate, the committee decided on a 7-bit code. This compromise made it possible to represent 128 different characters, sufficient to cover the Latin alphabet, numbers, and punctuation. A 6-bit code would have been too restrictive, while 8 bits would have increased transmission costs. The 7 bits also left the possibility of adding an eighth bit for error detection, a valuable function when telephone lines crackled.

ASCII was born in 1963, underwent a revision in 1967 before its final version in 1986. The designers reserved the first 32 positions for control characters, inherited from teleprinters, such as carriage return, line feed, and tabulation. The following 95 positions accommodated letters, numbers, and symbols. Nothing was left to chance in this organization. The numbers aligned to facilitate conversions, the letters followed alphabetical order, and punctuation found its logical place.

In November 1968, the National Bureau of Standards adopted ASCII as the first federal information processing standard. President Lyndon Johnson signed this decision, making ASCII mandatory for all US government computer purchases. Since the government was the sector’s largest customer, this measure pushed the entire industry toward ASCII.

In reality, 7-bit ASCII is generally integrated into an 8-bit code: either the additional bit is set to zero, or it serves for parity checking. This approach works well with computers that process information in groups of 8 bits. The parity bit detects transmission errors: in an even parity system, it adjusts to maintain an even number of 1 bits. If an error occurs during transfer, the count changes and signals the problem.

ASCII’s success inspired national variants. Canada developed its version for French characters, India created ISCII, Vietnam VISCII, Yugoslavia YUSCII. Each country adapted the code to its linguistic needs. In 1972, ASCII was integrated into the international standard ISO/IEC 646, which authorized certain national rearrangements. But ASCII had established itself as the de facto standard, sometimes creating confusion when other countries redefined certain positions.

The arrival of 16- and 32-bit computers opened the way for 8-bit extensions. These versions kept the original 128 ASCII characters and added 128 new positions. The IBM PC introduced code page 437, which replaced control characters with graphic symbols. Digital Equipment Corporation designed the multinational character set for its VT220 terminal, one of the first extensions designed for international use rather than graphics. The ISO/IEC 8859 standard eventually prevailed, derived from Digital’s system. Microsoft then developed Windows-1252, which added typographic symbols necessary for quality printing. These three systems—7-bit ASCII, ISO-8859-1, and Windows-1252—dominated computing until the late 2000s.

Unicode has since taken over from ASCII, capable of handling tens of thousands of characters. But Unicode’s designers had the wisdom to preserve compatibility: the 128 ASCII characters retain their original codes. ASCII is valid in UTF-8, the currently dominant encoding, making it a subset of Unicode.

More than sixty years after its birth, ASCII continues to structure our digital exchanges. When everything collapses, when sophisticated formats fail, ASCII endures. The Internet rests on it, communication protocols use it, and our smartphones still decode its characters. This exceptional longevity testifies to a remarkable design, the fruit of a rare industrial consensus.