Origination
of C-Programming Language and getting its Name
To understand
programming language you must be familiar with two words programming and
language. Language is the collection
of symbols, marks, sounds, gestures, icons and pictures that have special
meaning and are used by people(may even be any creature) for sharing emotions
or information among them. Programming is
the process of listing the jobs in a sequence that something/somebody should
have to be performed. So, programming language is the collection of notations
for describing computation to people and to the machines.
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C
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is a general-purpose programming language
initially developed by Dennis Ritchie
between 1969-1972; many of its principles and ideas were taken from earlier language
B and B’s earlier ancestors CPL (Combined Programming Language) and
BCPL(Basic Combined Programming
Language); which are developed by Martin Richards. CPL was developed with
the purpose of creating languages that were capable of both high level, machine
independent programming and would still allow the programmer to control the
behavior of individual bits of information. One major drawback of CPL was that
it was too large for use in many applications. In 1967, BCPL was created as
scaled down version of CPL while still retaining its basic features. In 1970 Ken Thomson, while working at Bell
Labs, took this process further by developing the B language. B was the scaled
down version of BCPL written specially for use in system programming. Finally in 1972, a coworker of Ken Thomson, Dennis Ritchie,
returned some of the generality found in BCPL to the B language in the process
of developing the language we now know as C. The logic behind the name of
B-programming was that it was first scaled down version of BCPL so B was used
to represent the first scaled down version and was the first character of BCPL;
and C-programming is the second scaled down version of BCPL and it uses the second
character of the BCPL to represent the whole programming language .
C’s power and
flexibility soon became apparent.
Because of this, the UNIX
operating system which was originally written in assembly language, was almost
immediately re-written in C. During the rest of 1970’s, C spread throughout
many colleges and universities because of it’s close ties to UNIX and
availability of C compiler.
The origin of C
is closely tied to the development of the UNIX operating system, originally
implemented in assembly language in PDP-7 by Ritchie and Thomson, incorporating
several ideas from colleagues. Eventually they decided to port the operating
system to PDP-11. B’s inability to take advantages of some of the PDP-11’s
features, notably byte addressability,
led to the development of an early version of C.
The original
PDP-11 version of the UNIX was developed in assembly language. By 1973, with
the addition of struct types, the C
language had become powerful enough that most operating system kernel implemented
in language other than assembly.
K&R C
In 1978, Brian
Kernighan and Dennis Ritchie published the first edition of The Programming Language. This book was
known to C programmers as “K&R” and served as an informal specification of
the language. The version of C that describes is commonly referred as K&R
C. The second edition of the book covers the ANSI C standard.
K&R
introduced several features and are listed below-
a)
Standard
I/O library,
b)
long int data type,
c)
unsigned int data type
d)
compound
assignment operators of the form =op(such as =-) were changed to the form op=
to remove the semantic ambiguity created by such construct as i=-10, which had been interpreted as
i= -10.
Even after the
publication of the 1989, C standard, for many years K&R C was still
considered the “lowest common denominator” to which C programmers restricted
themselves when maximum portability was desired; since many older compilers
were still in use, and because carefully written k&R C can be legal
standard C as well.
In early
versions of C, only functions that returned a non-int value needed to be
declared if used before the function definition; a function used without any
previous declaration was assumed to return type int.
In the years
following the publication of K&R C, several unofficial features were added
to the language, supported by compilers from AT&T and some other vendors.
These included:
a)
void functions(i.e.
function with no return value).
b)
Functions returning struct or union
types (rather than pointer).
c)
Assignment for struct data type.
d) Enumerated
type.
The large number of extensions and lack of agreement on a
standard library, together with the language popularity implemented the K&R
specification, led to the necessity of standardization.
ANSI C and
ISO C
During late 1970s and 1980s version of C were implemented
for wide variety of mainframe computers, minicomputers and microcomputers,
including the IBM PC, as its popularity began increase significantly.
In 1983, the American
National Standards Institute(ANSI) formed a committee, X3J11, to establish
a standard specification of C. X3J11
based the C standard in the UNIX implementation; however, the non-portable
portion of the UNIX C library was handed off to the IEEE working group 1003 to become the basis for the 1988 POSIX standard. In 1989, the C
standard was ratified as ANSI X3
159-1989 “Programming Language C”. This version of language is often
referred to as ANSI C, or C89.
In 1990, the ANSI C standard(with formatting changes) was
adopted by International Organization for Standardization(ISO) as ISO/ICE 9899:1990, which is sometime
called C90. Therefore, the term C89
and C90 refer to same programming language.
ANSI like other national standards bodies, no longer
develops the C standard independently, but defers to the international C
standard maintained by the working group ISO/ICE JTC1/SC22/WJ14. National
adaptation of an update to international standard typically occurs within a
year of ISO publication.
One of the C standardization process was to produce the
superset of K&R C, incorporating
many of the unofficial features subsequently introduced. The standard committee
also included several additional features such as function prototype(borrowed
from C++), void pointers, supports for international character sets and
locales, and processor enhancements. Although the syntax for parameter
declaration was argumented to include the style used in C++, the K&R
interface continued to be permitted, for compatibility with existing source
code.
C89 is supported by current C compilers, and most C code
being written today is based on it. Any program written only in standard C and
without any hardware dependent assumption will run correctly on any platform
with a confirming C implementation, with in its resource limits without such
precautions, programs may compile only on certain platform or with a particular
compiler.
C99
After the ANSI/ISO standardization process, the C Language
specification remained relatively static for several years. In 1995 Normative
Amendment 1 to the 1990 C standard was published, to correct some details and
to add more extensive support for international character sets. The C standard
was further revised in the late 1990’s, leading to the publication of ISO
9899:1999 in 1999, which is commonly referred to as “C99”. It has since been amended three times by
Technical Corrigenda.
C99 introduced several new features, including inline
functions, several new data types (including long long int and a complex
type to represent complex number), variable-length arrays, improved support for
IEEE 754 floating point, support for varadic macros, and support for on-line
comments beginning with //, as in BCPL or C++. Many of these had already been
implemented as extensions in several C compilers.
C99 is for the most part backward compatible with C90, but
stricter in some ways; in particular, a declaration that lacks a type specifier
no longer has int implicitly assumed. A standard macro –STDC-VERSION- is
defined with values 1999011 to indicate that C99 support is available GCC,
Solaris Studio, and other C compilers now support many or all of the new
features of C99.
C11
In 2007, work began on another revision of the C standard
informally called “C1X” until its official
publication on 2011-12-08. The C standards committee adopted guidelines to
limit the adaption of new features that had not been tested existing
implementations.
The C11 standard adds numerous new features of C and the
library, including type generic macro, anonymous structures, improved Unicode
support, atomic operations, multi-threading, and bounds-checked functions. It
also makes some portions of the existing C99 library optional and compatibility
with C++.
Embedded C
Historically, embedded C programming requires nonstandard
extensions to the C language in order to support exotic features such as
fixed-point arithmetic, multiple distinct memory banks, and basic I/O
operations.
In 2008, the C standards committee published a technical
report extending the C language to address these issues by providing a common
standard for all implementations to adhere to. It includes a number of features
not available in normal C, such as fixed-point arithmetic, named address
spaces, and basic I/O hardware addressing.
C is not a very low level language, nor a big one, and is
not specialized to any particular area of application. But its absence of
restriction and its generality make it more convenient and effective for many
tasks than supposedly more powerful languages. C is middle level language; this
doesnot mean that C is less powerful, harder to use, or less of less developed.
Instead C combines the advantages of a high-level language with the
functionalism of assembly language. Like the higher-level language, C provides
block structures, standalone functions, and some small amount of data typing.
It allows the manipulation of bits, bytes, words, and pointers, like assembly
but it abstracts the hardware away from the code so that something written in C
is very portable, meaning that a program can be easily adapted to run on
several different computers. This is the great thing for system programmers;
they can get the efficiency of assembly language programming without all the
fuss and then they have a highly portable program; it allows programmers to do
many things that probably would be caught as errors in high-level language.
This is both an advantage and disadvantage. For the inexperienced programmer,
it may be confusing when the behavior of a program is not correct. A high-level
language catches many more possible errors at compile time, C lacks the highly
typed environment that characterizes high-level languages.
According to Brian Kernighan co-author with Dennis Ritchie
of “The C Programming Language”.; “Although
the absence of some of features may seems like a grave of deficiency … keeping
the language down to modest size has real benefits.” Since, C is relatively
small; it can be described in small space and learned quickly. It has only 32
keywords to learn and support all type of conversion (QBASIC has 159 keywords).
Uses of C
C was initially used for system development work. But why
use C…???? mainly because it produces code that run nearly as fast as written
in assembly language. C is mostly used for writing the following types of
programming:
-Operating
System -Text
Editors
-Language
Compilers -Printer
Spoolers
-Assembly -Network
Drivers
-Databases -Utilities
Importance/Advantages
of programming in C
1)
Easy to understand
2)
Freedom of using different type of
data.
3)
Short listed words could be use.
4)
Efficient and fast programming.
5)
It can be used as mid-level
language.
6)
Any type of software and operating
system be developed with the help of C language.
All fields have technical words. These words are useful when
you communicate with people in your field. But they do not communicate with
outsiders. C also has its own technical words and reserved for self maintenance with special meaning and referred as keywords or reserved words. All of keywords are listed below with
corresponding version’s amendment.
Below this can be ignored
C89 has 32
keyboards
auto extern sizeof
break float static
case for struct
char goto switch
const if typedef
continue int union
default long unsigned
do register void
double return volatile
else short while
enum signed
C99 adds
five more keyboards
_bool inline
_complex restrict
_imaginary
C11 add
seven more keywords
_Alignas _Noreturn
_alignof _Static_Assert
_Atomic _thread_local
_generic
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