c programming bacics.

STRUCTURE OF C PROGRAM

Documentation section  
Header section  /#include<stdio.h>,<math.h>
Main() function/main()
   {
Declaration part/int,float,…a,b,c,d;
 Executable part /scanf(“%d%d%d”,&a,&b,&c);
D=a/b;
Printf(“d=%d”,d);
}

DATA TYPE

Char –hold one character and occupies one byte of space(‘A’,’*’,’8’,)
Int  - hold integral  quantities. Occupies 2byte of space ( int p, q,r;)
Float –hold floating point number . Occupies 4byte of space(float  avg,)
Double- hold double  floating point number . Occupies 8byte of space(float side, width;)

KEY WORDS
Auto, extern ,size of, break , floatn  , static ,case, for, struct ,char, goto, switch,
Const,it,typedef,continue,int,union,default,long,unsinged,do,register,Void ,double ,return ,volatile ,else ,short , while ,else  ,enum, signed.

ESCAPE SEQUENCE
A  black slash followed by such a special  character is called an ESCAPE SEQUENCE
1. \a  -    bell
2. \b – back space
 3. \t – horizontal tab
 4. \v – vertical tab
 5. \n – new line
6.\f – form feed
7.\r- carriage return
8. \”-double quote
9.\? - question mark
0.\o-null

OPERATORS IN  C

Arithmetic operators
Addition              +
Subtraction         –
Multiplication   *
Division              /
Modules              %  - reminder of operana1 divided by operand2

1.1 Relational operators
Equal                                          ==
Greater than                                >
Less than                                    <
Greater than or equal to               >=
Less than  or  equal to                 <=
Not equal                                    !=

1.2   Logical operator
     
AND                    &&
OR                        ||
NOT                       !

1.3   Assignment operators
Identifier = expression;
Identifier   - represent a variable(x=7,p=q;)
Expression -  represent  a  constant(x=y=4)

1.4   Increment and Decrement operators
Increment (++)
Decrement (--)

1.5  Conditional operator
Expression1? Expression 2:Expression3

1.6  Bitwise operators
&          AND
|          OR
^          x or
~        1’s complement
>>      shift right
<<       shift left

1.7  special operators

Comma operator
Size of   operator
Pointer operator
Member selection operator

HEADER FILES
#include<stdio.h>
The imprortant library  functions covered by stdio.h header file are;
gets()
getchar()
put()
putchar()
scanf()
print()

READING A CHARACTER
getchar()
getche()
getch()
getc()

INPUT/OUTPUT FUNCTIONS
scanf()
printf()


programming
1.program  to print name;
#include<stdio.h>
main()
{
clrscr();
printf(“INTO  MAN\n”);
printf(“nest (h)\n”);
getch();
}

DECISION MAKING
if
if(expression)
statement
1.2   if-else
        If (expression)
         statement -1
   else
         statement -2
1.3   nested if

If (expression-1)
  If (expression-2)
     Statement -1
else
   statement  -2
 else
   if (expression-3)
   statement-3
   else
  statement-4

1.4   go to
switch

LOOP STRUCTURES

while loop
while(expression)
statement

do-while loop
do
statement;
while(expression);

for loop
for((expression-1;expression-2;expression-3; statement;

while loop
-loop continuations conditions is checked at the beginning
-if  the  loop condition  fails statement will not be executed at all

Do-while
-continuation condition is checked at the end
 -statement will be executed at least ones

GLOBAL AND LOCAL VARIABLES
variables  which are declared before the beginning of a function is called is called global variables.  variables which are declared inside a function is called is called local variables

FUNCTION CALL

Function-name(argument-list);
Category of functions
functions with argument and return value.
functions with argument and  no return value.
functions with no  argument and no  return values.

passing arguments to functions
call by value
call by references

ARRAYS
The individual data items in an array a are called array elements
1.1 ONE-DIMENSIONAL ARRAYS
data –type array name [expression];
1.2   TWO-DIMENSIONAL ARRAYS
Type array –name [row_ size] [column _size];

MULTI DIMENSIONAL ARRAYS
Array whose elements are specified by three or more subscripts are called multi dimensional arrays.
 Data-type array-name[expressions1] [expressions2]…[expression3]

DYNANIC ARRAYS
Allocate memory to array at run time know as dynamic memory allocations and the arrays created at run time is  called dynamic arrays.

STRING ARRAYS
A  String is a group of characters .string is stored in an array of characters.
Char string-name[size];

STRUCTURES
A structure is collection of data item or variables of different data –types that is referenced under the same name
Struct tag-name
{
Data-type member1;
Data-type member2;
…………………………….
……………………………..
Data-type member n;
};

Unions
A union is syntactically the same as a structure .union is a  construct  that allows different  type of data items to share the same block of memory,

     union tag –name
{
      member1;
      member2;
       …………….
      ……………..
};

Pointers
The variables that holds the address of a data item is called pointer.

Data-type*ptVar;

Malloc ()
Malloc() function is one of the most commonly used functions which permit allocation of memory form the pool of free memory. This function reserves a block of memory of specified size and returns a pointer of type void.
Ptr=(cast-type*)malloc(byte-size);
 Ptr is pointer of type cast-type.


Calloc()
Calloc function is used for requesting memory space at run time for storing derived data type such as arrays and structure. While malloc() function allocates a single block of strong space ,calloc() allocates multiple block of storage, each of same size, and then sets all bytes to zero
Ptr=(cast-type*)calloc(n,elem-size);

STREAM
A  stream is a sequence of byte of data .A sequence of byte following in to a program is an input stream and a sequences of byte flowing out of a program is an output stream.

TYPES OF FILES
. Standard (stream oriented)I/O text files
. Standard (stream oriented)I/O binary files
. Standard (stream oriented)I/O files.
OPENING A DATA FILE
FILE*ptvar;
Ptvar=fopen(“file name”,”mode);

CLOSING A DATA FILE
fclose (ptvar);
fprintf()and fscanf()
These functions are formatted  i/o functions used to input/output the formatted data items .These  functions can also handle a group of mixed data simultaneously ,fprintf and  fsacnf functions behaves  exactly like printf and scanf functions  except  that they operate with disk fils.
fprintf ( fp” control string”, argument list);
fscanf ( fp” control string”, argument list);