BCA 2nd Sem Notes-Conditional compilation

• 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 library function 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

Conditional compilation

Conditional Compilation orders help to assemble a particular bit of the program or let us skip assemblage of some particular piece of the program dependent on certain conditions. In our past article, we have examined two such orders 'ifdef' and 'endif'. Right now will talk about #ifndef, #if, #else and #elif

Six directives are available to control conditional compilation

• #if
• #ifdef
• #ifndef
• #else
• #elif

The #if a directive 

 syntax:

#if constant-expression newline

This directive checks whether the constant-expression is true (nonzero). The operand must be a constant integer expression that does not contain any increment (++), decrement (- -), sizeof , pointer (*), address (&), and cast operators.

The #ifdef Directive

 syntax:

#ifdef identifier newline

This directive checks whether the identifier is currently defined. Identifiers can be defined by a #define directive or on the command line. If such identifiers have not been subsequently undefined, they are considered currently defined.

The #ifndef Directive

 syntax:

#ifndef identifier newline

This directive checks to see if the identifier is not currently defined.

The #else Directive

syntax:

#else newline

This directive delimits alternative source text to be compiled if the condition tested for in the corresponding #if , #ifdef , or #ifndef a directive is false. An #else a directive is optional.

The #elif Directive

 syntax:

#elif constant-expression newline

The #elif directive performs a task similar to the combined use of the else-if statements in C. This directive delimits alternative source lines to be compiled if the constant expression in the corresponding #if , #ifdef , #ifndef , or another #elif a directive is false and if the additional constant expression presented in the #elif the line is true. An #elif a directive is an option

The #endif Directive

 syntax:

#endif newline

This directive ends the scope of the #if , #ifdef , #ifndef , #else , or #elif directive.

The number of necessary #endif directives changes according to whether the elif or #else a directive is used. Consider the following equivalent examples:

#if true                             #if true
.                                    .
.                                    .
.                                    .
#elif true                           .
.                                    #else
.                                    #if false
.                                    .
#endif                               .
                                     .
                                     #endif
                                     #endif

Next TopicBitwise Operators

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