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Presented By :
Gaurav Juneja
Introduction
 C is a general purpose language which is
very closely associated with UNIX for which
it was developed in Bell Laboratories.
 Most of the programs of UNIX are written and
run with the help of 'C'.
 Many of the important ideas of 'c' stem are
from BCPL by Martin Richards.
 In 1972, Dennies Ritchie at Bell Laboratories
wrote C Language which caused a revolution in
computing world .
 From beginning C was intended to be useful for
busy programmers to get things done easily
because C is powerful,dominant and supple
language.
Why Name 'C' was given to this
language?
Many of the ideas of C language
were derived and taken from 'B'
language.
BCPL and CPL are previous
versions of 'B' language.
As many features came from B it
was named as 'C'.
ABOUT “C”
o C is a structured programming language
o C supports functions that enables easy maintainability of
code, by
breaking large file into smaller modules
o Comments in C provides easy readability
o C is a powerful language.
o C programs built from
• Variable and type declarations
• Functions
• Statements
• Expressions
- Structured and disciplined approach to
 C programming
language
program design.
C Program basic concepts using c  knoweledge
Structure Of “C” Programs
 Before going and reading the structure of
C programs we need to have a basic
knowledge of the following:
1.C's Character Set
2.C's Keywords
3.The General Structure of a 'C' Program
4.How To End A Statement
5.Free Format Language
6.Header Files & Library Functions
C's Character Set
C does not use every character set and key
found on
modern computers . The only characters that
C - Language uses for its programs are as
follows:
 A-Z all alphabets
 a-z all alphabets
 0-9
 # % & ! _ {} [] () $$$$ &&&& |
 space . , : ; ' $ "
 + - / * =
"Keywords" are words that have
special meaning to the C compiler.
Their meaning cannot be changed at
any instance.
Serve as basic building blocks for
program statements.
All keywords are written in only
lowercase.
The keywords
#include<stdio.h
>
#include<conio.h
>
void
main()
{ -- other
statements
}
Basic Structure Of “C” Programs
Header Files
Indicates Starting
of Program
Entry Point Of
Program
The files that are specified in the
include section is called as Header
File.
These are precompiled files that has
some functions defined in them.
We can call those functions in
our program by supplying
parameters.
 Header file is given an
extension .h .
Header files
 This is the “Entry Point” of a program.
When a file is executed, the start point
is the main function.
From main function the flow goes as
per the programmers choice.
There may or may not be other
functions written by user in a
program.
Main function is compulsory for any
C program.
Main function
 Type a program.
 Save it.
 Compile the program – This will generate an .exe
file (executable)
 Run the program (Actually the exe created out
of compilation will run and not the .c file)
 In different compiler we have different
option for compiling and running.
Running a ‘C’
Program
 The smallest individual units in a C program are
known as tokens. In a C source program, the basic
element recognized by the compiler is the "token." A
token is source-program text that the compiler does
not break down into component elements.
 C has 6 different types of tokens viz.
1. Keywords [e.g. float, int,
while]
2.Identifiers [e.g. main,
amount] 3. Constants [e.g. -
25.6, 100]
4. Strings [e.g. “SMIT”, “year”]
5. Special Symbols [e.g. {, }, [, ]
]
C - programs are written using these tokens and
the general syntax.
“C” language TOKENS
Strin
gs
Keywords in Ansi “C”
auto double register switch
break else return typedef
case enum short union
char etern signed unsigned
const float sizeof void
continue for static volatile
default goto struct while
do if int long
 They are programmer-chosen names to represent
parts of the program: variables, functions, etc.
 Cannot use C keywords as identifiers
 Must begin with alpha character or _, followed by
alpha, numeric, or _
 Upper- and lower-case characters are important
(case-
sensitive)
 Must consist of only letters, digits or underscore ( _ ).
 Only first 31 characters are significant.
 Must NOT contain spaces ( ).
The Identifiers
Constants in C are the fixed values that do not
change during the execution of a program.
Constants
CONSTANTS
Numeric constants Character constants
Integer
Constants
Real
Constants
Single
Character
Constants
String
Constants
• Integer Constants
– Refers to sequence of digits such as decimal integer, octal
integer and hexadecimal integer.
– Some of the examples are 112, 0551, 56579u, 0X2 etc.
• Real Constants
– The floating point constants such as 0.0083, -0.78,
+67.89 etc.
• Single Character Constants
– A single char const contains a single character enclosed within
pair of single quotes [ ‘ ’ ]. For example, ‘8’, ‘a’ , ‘i’ etc.
• String Constants
– A string constant is a sequence of characters enclosed in double
quotes [ “ ” ]; For example, “0211”, “Stack Overflow” etc.
Constants Examples
DECLARATIONS
 Constants and variables must be declared
before they can be used.
 A constant declaration specifies the type,
the name and the value of the constant.
 any attempt to alter the value of a
variable defined
 as constant results in an error
message by the compiler
 A variable declaration specifies the type,
the
name and possibly the initial value of the
variable.
 When you declare a constant or a variable,
the compiler:
 Reserves a memory location in which to store
the value of the constant or variable.
 Associates the name of the constant or
variable with the memory location.
• A Variable is a data name that is used to store
any data value.
• Variables are used to store values that can
be changed during the program execution.
• Variables in C have the same meaning as
variables in algebra. That is, they represent
some unknown, or variable, value.
x = a + b
z + 2 = 3(y - 5)
• Remember that variables in algebra are
represented by a single alphabetic
character.
What Are Variables in C?
Naming Variables
Variables in C may be given representations
containing multiple characters. But there are
rules for these representations.
Variable names in C :
 May only consist of letters, digits, and
underscores
 May be as long as you like, but only the first
31 characters are significant
 May not begin with a number
 May not be a C reserved word (keyword)
 Should start with a letter or an underscore(_)
 Can contain letters, numbers or underscore.
 No other special characters are allowed
including space.
Case Sensitivity
 C is a case sensitive language.
It matters whether an identifier, such as
a variable name, is uppercase or
lowercase.
 Example:
area
Area
AREA
ArEa
are all seen as different variables by
the compiler.
Declaring Variables
 Before using a variable, you must give the
compiler some information about the variable; i.e.,
you must declare it.
 The declaration statement includes the data type of
the
variable.
 Examples of variable
declarations: int length ;
float area ;
 Variables are not automatically initialized. For example,
after declaration
int sum;
the value of the variable sum can be anything
(garbage).
 Thus, it is good practice to initialize variables when they
are
declared.
• There are three classes of data types here::
• Primitive data types
– int, float, double, char
• Aggregate OR derived data types
– Arrays come under this category
– Arrays can contain collection of int or float or
char or double data
• User defined data types
– Structures and enum fall under this category.
Data types in ‘ansi c’
Data Types- different attributes
Type Size Representation Minimum range Maximum range
char, signed char 8 bits ASCII -128 127
unsigned char bool 8 bits ASCII 0 255
short, signed short 16 bits 2's complement -32768 32767
unsigned short 16 bits Binary 0 65535
int, signed int 16 bits 2's complement -32768 32767
unsigned int 16 bits Binary 0 65535
long, signed long 32 bits 2's complement -2,147,483,648 2,147,483,647
unsigned long 32 bits Binary 0 4,294,967,295
float 32 bits IEEE 32-bit 1.175495e-38 3.4028235e+38
double 32 bits IEEE 32-bit 1.175495e-38 3.4028235e+38
long double 32 bits IEEE 32-bit 1.175495e-38 3.4028235e+38
/* HELLO.C -- Hello, world
*/
#include <stdio.h>
Void main()
{
printf("Hel
lo, world
n");
Getch();
}
Example of “C” Program
C Program basic concepts using c  knoweledge

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C Program basic concepts using c knoweledge

  • 2. Introduction  C is a general purpose language which is very closely associated with UNIX for which it was developed in Bell Laboratories.  Most of the programs of UNIX are written and run with the help of 'C'.  Many of the important ideas of 'c' stem are from BCPL by Martin Richards.  In 1972, Dennies Ritchie at Bell Laboratories wrote C Language which caused a revolution in computing world .  From beginning C was intended to be useful for busy programmers to get things done easily because C is powerful,dominant and supple language.
  • 3. Why Name 'C' was given to this language? Many of the ideas of C language were derived and taken from 'B' language. BCPL and CPL are previous versions of 'B' language. As many features came from B it was named as 'C'.
  • 4. ABOUT “C” o C is a structured programming language o C supports functions that enables easy maintainability of code, by breaking large file into smaller modules o Comments in C provides easy readability o C is a powerful language. o C programs built from • Variable and type declarations • Functions • Statements • Expressions - Structured and disciplined approach to  C programming language program design.
  • 6. Structure Of “C” Programs  Before going and reading the structure of C programs we need to have a basic knowledge of the following: 1.C's Character Set 2.C's Keywords 3.The General Structure of a 'C' Program 4.How To End A Statement 5.Free Format Language 6.Header Files & Library Functions
  • 7. C's Character Set C does not use every character set and key found on modern computers . The only characters that C - Language uses for its programs are as follows:  A-Z all alphabets  a-z all alphabets  0-9  # % & ! _ {} [] () $$$$ &&&& |  space . , : ; ' $ "  + - / * =
  • 8. "Keywords" are words that have special meaning to the C compiler. Their meaning cannot be changed at any instance. Serve as basic building blocks for program statements. All keywords are written in only lowercase. The keywords
  • 9. #include<stdio.h > #include<conio.h > void main() { -- other statements } Basic Structure Of “C” Programs Header Files Indicates Starting of Program Entry Point Of Program
  • 10. The files that are specified in the include section is called as Header File. These are precompiled files that has some functions defined in them. We can call those functions in our program by supplying parameters.  Header file is given an extension .h . Header files
  • 11.  This is the “Entry Point” of a program. When a file is executed, the start point is the main function. From main function the flow goes as per the programmers choice. There may or may not be other functions written by user in a program. Main function is compulsory for any C program. Main function
  • 12.  Type a program.  Save it.  Compile the program – This will generate an .exe file (executable)  Run the program (Actually the exe created out of compilation will run and not the .c file)  In different compiler we have different option for compiling and running. Running a ‘C’ Program
  • 13.  The smallest individual units in a C program are known as tokens. In a C source program, the basic element recognized by the compiler is the "token." A token is source-program text that the compiler does not break down into component elements.  C has 6 different types of tokens viz. 1. Keywords [e.g. float, int, while] 2.Identifiers [e.g. main, amount] 3. Constants [e.g. - 25.6, 100] 4. Strings [e.g. “SMIT”, “year”] 5. Special Symbols [e.g. {, }, [, ] ] C - programs are written using these tokens and the general syntax. “C” language TOKENS Strin gs
  • 14. Keywords in Ansi “C” auto double register switch break else return typedef case enum short union char etern signed unsigned const float sizeof void continue for static volatile default goto struct while do if int long
  • 15.  They are programmer-chosen names to represent parts of the program: variables, functions, etc.  Cannot use C keywords as identifiers  Must begin with alpha character or _, followed by alpha, numeric, or _  Upper- and lower-case characters are important (case- sensitive)  Must consist of only letters, digits or underscore ( _ ).  Only first 31 characters are significant.  Must NOT contain spaces ( ). The Identifiers
  • 16. Constants in C are the fixed values that do not change during the execution of a program. Constants CONSTANTS Numeric constants Character constants Integer Constants Real Constants Single Character Constants String Constants
  • 17. • Integer Constants – Refers to sequence of digits such as decimal integer, octal integer and hexadecimal integer. – Some of the examples are 112, 0551, 56579u, 0X2 etc. • Real Constants – The floating point constants such as 0.0083, -0.78, +67.89 etc. • Single Character Constants – A single char const contains a single character enclosed within pair of single quotes [ ‘ ’ ]. For example, ‘8’, ‘a’ , ‘i’ etc. • String Constants – A string constant is a sequence of characters enclosed in double quotes [ “ ” ]; For example, “0211”, “Stack Overflow” etc. Constants Examples
  • 18. DECLARATIONS  Constants and variables must be declared before they can be used.  A constant declaration specifies the type, the name and the value of the constant.  any attempt to alter the value of a variable defined  as constant results in an error message by the compiler  A variable declaration specifies the type, the name and possibly the initial value of the variable.  When you declare a constant or a variable, the compiler:  Reserves a memory location in which to store the value of the constant or variable.  Associates the name of the constant or variable with the memory location.
  • 19. • A Variable is a data name that is used to store any data value. • Variables are used to store values that can be changed during the program execution. • Variables in C have the same meaning as variables in algebra. That is, they represent some unknown, or variable, value. x = a + b z + 2 = 3(y - 5) • Remember that variables in algebra are represented by a single alphabetic character. What Are Variables in C?
  • 20. Naming Variables Variables in C may be given representations containing multiple characters. But there are rules for these representations. Variable names in C :  May only consist of letters, digits, and underscores  May be as long as you like, but only the first 31 characters are significant  May not begin with a number  May not be a C reserved word (keyword)  Should start with a letter or an underscore(_)  Can contain letters, numbers or underscore.  No other special characters are allowed including space.
  • 21. Case Sensitivity  C is a case sensitive language. It matters whether an identifier, such as a variable name, is uppercase or lowercase.  Example: area Area AREA ArEa are all seen as different variables by the compiler.
  • 22. Declaring Variables  Before using a variable, you must give the compiler some information about the variable; i.e., you must declare it.  The declaration statement includes the data type of the variable.  Examples of variable declarations: int length ; float area ;  Variables are not automatically initialized. For example, after declaration int sum; the value of the variable sum can be anything (garbage).  Thus, it is good practice to initialize variables when they are declared.
  • 23. • There are three classes of data types here:: • Primitive data types – int, float, double, char • Aggregate OR derived data types – Arrays come under this category – Arrays can contain collection of int or float or char or double data • User defined data types – Structures and enum fall under this category. Data types in ‘ansi c’
  • 24. Data Types- different attributes Type Size Representation Minimum range Maximum range char, signed char 8 bits ASCII -128 127 unsigned char bool 8 bits ASCII 0 255 short, signed short 16 bits 2's complement -32768 32767 unsigned short 16 bits Binary 0 65535 int, signed int 16 bits 2's complement -32768 32767 unsigned int 16 bits Binary 0 65535 long, signed long 32 bits 2's complement -2,147,483,648 2,147,483,647 unsigned long 32 bits Binary 0 4,294,967,295 float 32 bits IEEE 32-bit 1.175495e-38 3.4028235e+38 double 32 bits IEEE 32-bit 1.175495e-38 3.4028235e+38 long double 32 bits IEEE 32-bit 1.175495e-38 3.4028235e+38
  • 25. /* HELLO.C -- Hello, world */ #include <stdio.h> Void main() { printf("Hel lo, world n"); Getch(); } Example of “C” Program