BCA 2nd Sem Notes-Macro substitution directives

• 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

Macro substitution directives

Macro substitution has a name and replacement text, defined with #define directive. The preprocessor simply replaces the name of macro with replacement text from the place where the macro is defined in the source code.
Simple Macro Substitution Directive in c:
syntax:
#define identifier value
Example:
#define VALUE 10           //capital identifier name
D=VALUE-5;
Answer is 3

A macro is a segment of code which is replaced by the value of macro. Macro is defined by #define directive. There are two types of macros:

1. Object-like Macros
2. Function-like Macros

Object-like Macros

The object-like macro is an identifier that is replaced by value. It is widely used to represent numeric constants. For example:

#define PI 3.14

Here, PI is the macro name which will be replaced by the value 3.14.

Function-like Macros

The function-like macro looks like function call. For example

#define MIN(a,b) ((a)<(b)?(a):(b)) 

C Predefined Macros

ANSI C defines many predefined macros that can be used in c program.

No.	Macro	Description
1	_DATE_	represents current date in "MMM DD YYYY" format.
2	_TIME_	represents current time in "HH:MM:SS" format.
3	_FILE_	represents current file name.
4	_LINE_	represents current line number.
5	_STDC_	It is defined as 1 when compiler complies with the ANSI standard.

C predefined macros example

File: simple.c

1. #include<stdio.h>  
2.  int main(){    
3.    printf("File :%s\n", __FILE__ );    
4.    printf("Date :%s\n", __DATE__ );    
5.    printf("Time :%s\n", __TIME__ );    
6.    printf("Line :%d\n", __LINE__ );    
7.    printf("STDC :%d\n", __STDC__ );      
8.    return 0;  
9.  }    

Output:

File :simple.c
Date :Dec 6 2015
Time :12:28:46
Line :6
STDC :1

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