PROCEDURE ORIENTED PROGRAMMING

PROCEDURE ORIENTED PROGRAMMING:

              *COBOL,FORTRAN and C is commonly known as procedure oriented programming.

                  *In POP, the problem is viewed as sequence of things to be done such as reading,calculating and printing.

                 *It is a top down approach.    

HISTORY OF C: 

          *The first computer language was ALGOL introduced in 1960.It is a structured programming.

          *Martin Richards developed a language called as BCPL(Basic Combined Programming Language) in 1967.

          *Ken Thompson created a language using many features of BCPL and called as B.

          *B was used to early version of UNIX operating system at Bell Laboratories.

          *Both B and BCPL were Typeless system programming languages.

          *C language was evolved from ALGOL,BCPL and B languages by Dennis Ritchie at the Bell Laboratories in 1972.

          *C uses many concepts from these languages and added the concept of Data types end other powerful features.

          *In 1983 ANSI(American National Standards Institute) appointed a technical committee defined a standard for C.

          *The committee approved a version of C in December 1989 which is known as ANSI C also referred as C89.

          *Then it was approved by ISO.

          *Current version of C is C99.          

IDENTIFIER:

          *An identifier is a symbolic name used to refer to an entity.Such as Data type,Constant,Variable,Function,Array etc in a program.

VARIABLE AND CONSTANT:

          *Variable is an identifier used for storing data in a program. The value of the variable may be changed during execution of the program.

          *Constant is a fixed value. It never changes its value during execution.

 Types of Constants:

                  1)Integer Constants(123,-321,xbcd)

                  2)Real Constants(92.3,0.65e4)

                  3)Single character Constants('5','x',';')

                  4)String Constants("hello","1087")

                  5)Backslash Constants('\t','\n')

                       

SCALAR DATA TYPE AND DERIVED DATA TYPE:

                *A Scalar data type is used for representing a single value only.

                 Such as int,float,char,double.

                *A Derived data type is used for representing a single value or multiple value.

                * It is derived from Scalar data type. Such as Array,Structure,Union and Functions.

                                                

 TOKEN:

           *Token is a individual entity of a program. A compiler identifies and splits a  program into  no of tokens.

             C has six types of tokens.

                      1)Keywords

                      2)Identifier

                      3)Constants

                      4)Strings

                      5)Special symbols

                      6)Operators

KEYWORDS:

                     *All Key words have fixed meanings and these meaning cannot be changed.

                         ANCI C has defined 32 keywords.

                         C99 has added 5 more keywords.

                                        1)_Bool

                                        2)_Complex

                                        3)_Imaginary

                                           4)inline

                                        5)restrict       

OPERATOR AND OPERAND:

                        *An operator is a symbol that tells a computer to perform certain mathematical or logical manipulations.

CLASSIFICATION OF OPERATORS IN C:

               1)Arithmetic operator(+,-,*,/,%)

               2)Relational operator(<,<=,>,>=,==,!=)

               3)Logical operator(&&-AND,||-OR,!-NOT)

               4)Assignment operator(=)

                           3 types of assignments:

                                             i)Simple assignment(a=10)

                                            ii)Compound assignment(a+=5)

                                            iii)Assignment(a=b=c=0)

               5)Increment and Decrement operators(++,--)

                                 The execution of n++ is much faster than execution of n=n+1.

                                          n++ requires single machine instruction but n=n+1 requires more instructions to carry out this operation.

               6)Conditional operators()

               7)Bitwise operators(&-bw AND,|-bw OR,^-bw EXOR,<<-shift left,>>-shift right)

               8)Special operators (comma,sizeof)

 EXPRESSION:

      *A valid combination of constants,variables,and operators constitutes an expression.

DATA TYPES:

                        *ANCI C supports three classes of data types

                                1)primary or fundamental data type

                                2)Derived data type(Array,Functions,Pointers)

                                3)User defined data type(Structures,Unions,Enumerations)

                1)primary data types:

                            1)Integer has two types.

                                          1)Signed(short int=1 byte,int,long int=4 byte)

                                          2)Unsigned(Unsigned short int,unsigned int,unsigned long int)

                             2)Float has three types:

                                          1)float=4 byte

                                          2)double=8 byte

                                          3)long double =10 byte

                            3)Char has three types(char,signed char,unsigned char)=1 byte

DECISION MAKING:

                                     *C language possesses such decision making capabilities by supporting the following elements:

                                         1)if statement

                                                   1)simple if statement

                                                   2)if...else statement

                                                   3)Nested if....else statement

                                                   4)else if ladder

                                         2)switch statement

                                         3)Conditional statement

                                         4)goto statement            

LOOPING:

                            1)The while statement(Entry Controlled Loop)

                            2)The do statement(Exit Controlled Loop)

                            3)The for statement (Entry Controlled Loop)

What is difference between Entry controlled

 and Exit Controlled?

          *In Entry controlled loop the test condition is checked first and if the condition is true then the block of sttaement in the loop body will be executed. While in exit controlled loop the body of loop will be executed first then check the condition.

  

ARRAYS:

                       *An array is a fixed size sequenced collection of elements of same datatype.

 Types of array:

             1)One-dimensional arrays (datatype arr-name[size])

             2)Two-dimensional arrays(datatype arr-name[row-size][col-size])

             3)Multi-dimensional arrays(datatype arr-name[s1][s2][s3]...[sn])                                                                                                             

 STRING:

                     *String is a sequence of chars that is treated as a single data item.

         Ways of getting string:

                        1)scanf("%c",n)

                        2)ch=getchar()->only for single word

                        3)gets(a)

                        4)c=getc(fp2)  

       Ways of display string:

                        1)printf("%c",n)

                        2)putchar(ch)

                        3)puts(n)

                        4)putc(c,fp1)

                    * fprintf,fscanf handle a group of mixed data simultaneously.

EX:

fprintf(fp,'control string',list)

STRING HANDLING FUNCTIONS:

                       1)strcat function(str1,str2)

                       2)strcmp function(str1,str2)

                       3)strlen function(str)

FUNCTIONS:

                              *Function is a sub program that can perform any particular task.

                     Two types of functions:

                        1)library functions or predefined(printf,strcat)

                        2)User defined functions

CATAGORY OF FUNCTIONS:

                        1)Functions with no argument and no return values.

                        2)Functions with arguments and no return values.

                        3)Function with no argument but return a value.

                        4)Function that return multiple values.   

STORAGE CLASS:   

                          *In C all variables have a storage class:They are

                         1)Automatic variables(Local or internal variables)

                         2)External variables(Global)

                         3)Static variables()

                         4)Register variables                          

  1)Automatic variables:

                          *These are declared inside the function. They are created when the function is called and destroyed automatically when the function is executed.    

 2)External variables:

                          *Variables that are  both alive and active throughout the entire program is external variables.

EX: extern int a=5;

3)Static variable:

                          *The value of static variables  persists until the end of the program.     

EX: static int count=5;

4)Register variable:

                        *In register variable, variables are stored in one of the machine register. Because the register access is much faster than a memory access.

EX: register int count;

STRUCTURE:

               *It is a collection of data items of  different types  using a single name.

UNION:

              *Union is similar to structure. The distinction   between them in terms of storage.

               *In structure, all member has its own storage location.

               *In union, all member uses the same location.

POINTER:

               What is a pointer and does Java support pointers?

Pointer is a reference handle to a memory location. Improper handling of pointers leads to memory leaks and reliability issues hence Java doesn't support the usage of pointers.

               *Pointers contain memory address as their values. Since  these memory addresses are locations in the computer memory where the data are stored.

      Features of pointers:

                *pointers reduce length and complexity of programs.

                *They increase the execution speed and thus they reduce the program execution time.

Disadvantages:

                * By using pointer the hacker can get the address of source code and can change them. 

             *EX  const  int x=5;

             *In the above ex the value of x can't be change.But using pointer it is possible.

FILE:

              *A file is a place on the disk where a group of related data is stored.

              *The basic file operations are

                 1)Naming a file

                 2)Opening a file

                 3)Reading data from a file

                 4)Writing data to a file.

                 5)Closing a file

 1)Naming and opening a file and closing a file:

                 *FILE *fp;

                   fp=fopen('filename','mode');

mode->specifies the purpose of file opening.

           r=open the file reading only

           w=open the file for writing only

           a=open the file to adding data to it.  

To close a file:

                   *fclose(file pointer);

MEMORY ALLOCATON FUNCTIONS:
                    *malloc()

                    *calloc(allocating space for arrays)

                    *free(frees previously allocated space)

                    *realloc(modofies the size of previously allocated space)

 PREPROCESSOR DIRECTORIES:

                       *#define 

                      *#undef       *#ifndef

                      *#Include     *#if

                      *#ifdef     *#else