C language preliminaries

Introduction to C Language
C Tokens
Structure of C Program
Compiling and Executing a C Program

C Language Preliminaries

Abhineet Anand

Computer Science and Engg. Department
University of Petrolium and Energy Studies, Dehradun

November 19, 2012

Abhineet Anand C Language Preliminaries

Introduction
C Tokens
History of C
Characteristics of C

Introduction

C is a high level language.
It also has the capability of low level programming. So,
sometimes also referred as middle level Programming
Language.
Best Programming Language for learning procedural
programming approach.
It was developed at the Bell Laboratory, USA (now AT & T),
in 1972.
It is the outcome of Dennis Ritchie and Brian Kernighan.


Introduction
C Tokens
History of C

History of C

C is derived from two early programming languages such
as BCPL (Basic Combined Programming Language) and B
language developed by Ken Thompson.
In 1972 Dennis Ritchie developed a new version of B and
named it as C.
In 1978, Dennis Ritchie and Brian Kernighan jointly
published a detailed description of the C language
document. It is Known as K & R C.
Some of Shortcomings of K & R C implementation are
overcome by ANSI (American National Standard Institute)
standards.


Introduction
C Tokens
History of C


C is a general purpose & structured programming
language, which helps in development of system software.
It has rich set of operators.
It provides compact representation for expression.
It allows manipulation of internal processor registers.
Portability: any C program can be run in different machine
with no modiﬁcation.
Rich set of data types and less number of reserved words.
Pointer arithmetic and manipulation.
Ability to extend itself by adding fuctions to its library.


C Tokens C Tokens
Structure of C Program Keywords and Identiﬁers

C Tokens

The Basic and Smallest units of any programming
language is known as tokens. When a complier complies a
program, it recognises those basic units.
There are six types of tokens in C. They are:
Keywords
Identiﬁers
Constants
Strings
Operators
Special Symbols.
Each of these tokens is formed with one or more
charecters of C language.


C Tokens C Tokens

Keywords

Every word in C program is either a keyword or an identifer.
All Keywords must be written in lowercase letters.
C is case sensitive language.
Keywords supported by ANSI C are:
auto, break, case, char, const, continue, default, do,
double, else, enum, extern, ﬂoat, for, goto, if, int, long,
register, short, signed, sizeof, static, struct, switch, typedef,
union, unsigned, void, volatile & while.


C Tokens C Tokens

Identifiers

Identifiers are the names given to program elements such
as variables, arrays and fuctions.
These are sequence of alphabets and digits.
Rules for forming identifers names:
First charecter must be an alphabet or an underscore.
No special Charecter or punctuation symbols are allowed
except the underscore "_".
No two successive underscore are allowed.
Keywords should not be used as identifiers.


C Tokens
Preprocessor Statements
Declarations


preprocessor statement
global decleration;
main( )
{
decleration;
statement;
}
user deﬁned function


C Tokens
Declarations


Begin with # symbol, also called the preprocessor
directives.
Direct the C preprocessor to include header files and also
symbolic constants into C program. Few Statements :
# include < stdio.h > : for standard input/output functions.
# include "Test.h" : for file inclusion of the header files.
# deifne NULL 0 : for defining symbolic constant, NULL=0


C Tokens
Declarations

Global Declarations

Variable or function whose existance is known in main( )
function and other user deﬁned function, are called the
global variable.
Its decleartion is known as global declarations.
Excuation of C program starts with main( ).


C Tokens
Declarations

Declarations

Variable Decleration: All Variables, array, function used in
C program are decleared and may be initialized with their
basic data types.
Statements: the instruction to the computer to perform
some speciﬁc task. They may be:
Arithmetic Statements.
Input/output Statements.
Control Statements.
Other Statements.
Comments: explantory notes on some instruction, which
are not executed and enclosed with in /* & */.


C Tokens
Standard Procedure
Selecting OS


Compiling a C program means translating it into machine
language.C Compiler does that for C pragrams.
Various tools are availble which gives the facility of writing,
editing, debugging and excuting C language program.
This type of environment is known as Inetegrated
Development Environment (IDE).
Examples : Turbo C, Borland C/C++, ANSI C and many
more.


C Tokens
Standard Procedure
Selecting OS

Standard Procedure

There are basically ﬁve steps in the sucessful execution of a
program:
Creating a program ﬁle (Source File).
Saving the program (with .c as extension).
Compliation.
Linking system library function.
Running (executing) the program.


C Tokens
Standard Procedure
Selecting OS

Selecting OS

DOS Platform:
Any of the C program environment may be used which are
IDE.
Unix Platform:
Any of the Unix text editor is used to type the C Program,
with ﬁle extention of .c.


C Tokens
Standard Procedure
Selecting OS

Selecting OS cont..

Now, a C compiler is used to complie the program.
Normally, CC complier is availeble in Unix. So,
cc filename.c
This gives the output as a excutable file named a.out.
Now, this excutable file can be run through
./a.out
on command prompt of unix.


C Tokens

THANK YOU


C language preliminaries

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C language preliminaries