BCA 2nd Sem Notes-C Preprocessor Definition

• UNIT-I (Array)

Definition

Declaration & initialization of 1D 

Accessing array elements

Displaying array elements

Sorting arrays

Arrays and function

Declaration & initialization of 1D

Accessing and Displaying

Memory representation of array [Row Major, Column Major]

Multidimensional array

UNIT-II (Pointers)

Definition

Declaration & initialization

Indirection operator

address of operator

pointer arithmetic

dynamic memory allocation

arrays and pointers

function and pointers

UNIT-III (Strings)

Definition

Declaration & initialization

standard libraryfunction strlen()

strlen(),strcpy(),strcat() ,strcmp()

Implementation without using standard library functions

UNIT-IV (Structures)

Definition

Declaration & initialization

Accessing fields

structure operations

Nested structures

Union: Definition  declaration

Differentiate between Union and structure

UNIT-V                                  (C Preprocessor)

Definition
Macro substitution directives
File inclusion directives
Conditional compilation
Bitwise Operators
Shift operators
Masks
Bitfield

UNIT-VI                                (File Handling)

Definition of Files,
Opening modes of files
Standard function
fopen(), fclose(),               feof() fseek(),                     fewind()
Using text files
fgetc(), fputc(),               fscanf()

Program's in C

Definition

The C Preprocessor is not a part of the compiler, but is a separate step in the compilation process.

Preprocessor programs give preprocessors orders which advise the compiler to preprocess the source code before gathering. These preprocessor orders start with a '#' (hash) image. This ('#') image toward the start of an announcement in a C/C++ program demonstrates that it is a pre-processor order. We can put these preprocessor mandates anyplace in our program

There are 4 main types of preprocessor directives:

1. Macros
2. File Inclusion
3. Conditional Compilation
4. Other directives

1. Macros: Macros are a bit of code in a program that is given some name. At whatever point this name is experienced by the compiler replaces the name with the real bit of code. The '#define' mandate is utilized to characterize a full scale. Let us currently comprehend the large scale definition with the assistance of a program:

#include <stdio.h>

  

// macro definition

#define HIGHT 5

int main()

{

    for (int i = 0; i < HIGHT; i++) {

        printf("%d \n",i);

    }

  

    return 0;

Output:

0
1
2
3
4

In the above program, when the compiler executes the word HIGHT it replaces it with 5. The word 'HIGHT' in the large macro definition is known as a macro template and '5' is a macro expansion

2. File Inclusion: This kind of preprocessor order advises the compiler to remember a document for the source code program. There are two sorts of records which can be incorporated by the client in the program:

1. Header File or Standard files: these documents contain the meaning of pre-characterized capacities like printf(), scanf() and so forth. These records must be incorporated for working with these capacities. Diverse capacity is proclaimed in various header records. For instance standard, I/O functions are in 'iostream' document though works which perform string activities are in 'string' record Syntax:#include< file_name >
2. user defined files: When a program becomes very large, it is good practice to divide it into smaller files and include whenever needed

          Syntax  #include"filename"

3. Conditional Compilation: Conditional Compilation directives are type of directives which helps to compile a specific portion of the program or to skip compilation of some specific part of the program based on some conditions. This can be done with the help of two preprocessing commands ‘ifdef‘ and ‘endif‘.
Syntax:

#ifdef macro_name
    statement1;
    statement2;
    statement3;
    .
    .
    .
    statementN;
#endif

4. Other directives: Apart from the above directives there are two more directives which are not commonly used. These are:

1. #undef Directive: 
2. #pragma Directive: used #pragma startup and #pragma exit

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All preprocessor commands begin with a hash symbol (#). It must be the first nonblank character, and for readability, a preprocessor directive should begin in the first column. The following section lists down all the important preprocessor directives −

Sr.No.	Directive & Description
1	#define Substitutes a preprocessor macro.
2	#include Inserts a particular header from another file.
3	#undef Undefines a preprocessor macro.
4	#ifdef Returns true if this macro is defined.
5	#ifndef Returns true if this macro is not defined.
6	#if Tests if a compile time condition is true.
7	#else The alternative for #if.
8	#elif #else and #if in one statement.
9	#endif End preprocessor conditional.
10	#error Prints error message on stderr.
11	#pragma Issues special commands to the compiler, using a standardized method.

Next TopicMacro substitution directives

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