Development of C
Ritchie

System as well as a small group of researchoriented

industrial, academic, and government organizations

outside our company, its real growth began only after portability had been achieved. Of

particular note were the System III and System V versions of the system from the emerging Computer

Systems division of AT&T, based on work by the company’s development and research

groups, and the BSD series of releases by the University of California at Berkeley that derived

from research organizations in Bell Laboratories.

During the 1980s the use of the C language spread widely, and compilers became available

on nearly every machine architecture and operating system; in particular it became popular as a

programming tool for personal computers, both for manufacturers of commercial software for

these machines, and for endusers

interesting in programming. At the start of the decade, nearly

every compiler was based on Johnson’s

compiler products.

pcc; by 1985 there were many independentlyproduced

Standardization

By 1982 it was clear that C needed formal standardization. The best approximation to a

standard, the first edition of K&R, no longer described the language in actual use; in particular, it

mentioned neither the

only after it was published did the language support assigning them, passing them to and

from functions, and associating the names of members firmly with the structure or union containing

them. Although compilers distributed by AT&T incorporated these changes, and most of the

purveyors of compilers not based on

authoritative description of the language.

The first edition of K&R was also insufficiently precise on many details of the language,

and it became increasingly impractical to regard

embody even the language described by K&R, let alone subsequent extensions. Finally, the

incipient use of C in projects subject to commercial and government contract meant that the

imprimatur of an official standard was important. Thus (at the urging of M. D. McIlroy), ANSI

established the X3J11 committee under the direction of CBEMA in the summer of 1983, with the

goal of producing a C standard. X3J11 produced its report [ANSI 89] at the end of 1989, and

subsequently this standard was accepted by ISO as ISO/IEC 98991990.

From the beginning, the X3J11 committee took a cautious, conservative view of language

extensions. Much to my satisfaction, they took seriously their goal: ‘to develop a clear, consistent,

and unambiguous Standard for the C programming language which codifies the common,

existing definition of C and which promotes the portability of user programs across C language

environments.’ [ANSI 89] The committee realized that mere promulgation of a standard does not

make the world change.

X3J11 introduced only one genuinely important change to the language itself: it incorporated

the types of formal arguments in the type signature of a function, using syntax borrowed

from C++ [Stroustrup 86]. In the old style, external functions were declared like this:

void or enum types. While it foreshadowed the newer approach to structures,pcc quickly picked up them up, there remained no complete,pcc as a ‘reference compiler;’ it did not perfectly

double sin();

which says only that

floatingpoint)

value. In the new style, this better rendered

sin is a function returning a double (that is, doubleprecision

double sin(double);

to make the argument type explicit and thus encourage better type checking and appropriate conversion.

Even this addition, though it produced a noticeably better language, caused difficulties.

The committee justifiably felt that simply outlawing ‘oldstyle’

function definitions and declarations

was not feasible, yet also agreed that the new forms were better. The inevitable compromise

was as good as it could have been, though the language definition is complicated by permitting

both forms, and writers of portable software must contend with compilers not yet brought up to

standard.

X3J11 also introduced a host of smaller additions and adjustments, for example, the type