Vcs29
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The document discusses different approaches to dynamically allocating memory for arrays in C programs. It covers using malloc() to allocate memory at runtime rather than compile-time, avoiding memory leaks, and creating linked lists in memory using structs. The examples show how to dynamically allocate memory for arrays, add elements to linked lists using structs, and iterate through linked lists without memory leaks.
![Arrays
main( )
{
int m1, m2, m3, i, per [ 1 0 ] ;
for ( i = 0 ; i <= 9 ; i++ )
{
printf ( ”Enter marks” ) ;
scanf ( ”%d %d %d”, &m1, &m2, &m3 ) ;
[ i ]
per = ( m1 + m2 + m3 ) / 3 ;
printf ( ”%d”, per [ i ] ) ;
} }
No Flexibility](https://image.slidesharecdn.com/vcs29-140830105510-phpapp01/85/Vcs29-1-320.jpg)
![Better Still...
int *p[ ] ;
char ch = ’Y’ ;
while ( ch = = ’Y’ )
{
scanf ( ”%d %d %d”, &m1, &m2, &m3 ) ;
per = ( m1 + m2 + m3 ) / 3 ;
pp malloc [= i ]( =in (( t i*2 n ) t m* ;
)a mlloacll o( c2 () 2; ) ;
ch = getche( ) ;
}
p p p
55 63 28 45
Memory Leaks
?
p = malloc ( 2 ) ;
**p( p= + p ie )r =; per ;
printf ( ”Another student y/n” ) ;](https://image.slidesharecdn.com/vcs29-140830105510-phpapp01/85/Vcs29-4-320.jpg)
Vcs29
- 1. Arrays main( ) { int m1, m2, m3, i, per [ 1 0 ] ; for ( i = 0 ; i <= 9 ; i++ ) { printf ( ”Enter marks” ) ; scanf ( ”%d %d %d”, &m1, &m2, &m3 ) ; [ i ] per = ( m1 + m2 + m3 ) / 3 ; printf ( ”%d”, per [ i ] ) ; } } No Flexibility
- 2. # include ”alloc.h” main( ) { int m1, m2, m3, i, per ; int *p ; printf ( ”Enter no. of students” ) ; scanf ( ”%d”, &n ) ; for ( i = 0 ; i < n ; i++ ) malloc ( n * 2 ) ; { scanf ( ”%d%d%d”, &m1, &m2, &m3 ) ; per = ( m1 + m2 + m3 ) / 3 ; * ( p + i ) = per ; } for ( i = 0 ; i < n ; i++ ) printf ( ”%d”, * ( p + i ) ) ; } MMeemmoorryy n* 2 p Dynamic Allocation p = malloc ( n * 2 ) ; ( int * ) malloc ( n * 2 ) ;
- 3. Memory Allocation Array Static Compile Time malloc( ) Dynamic Execution Time
- 4. Better Still... int *p[ ] ; char ch = ’Y’ ; while ( ch = = ’Y’ ) { scanf ( ”%d %d %d”, &m1, &m2, &m3 ) ; per = ( m1 + m2 + m3 ) / 3 ; pp malloc [= i ]( =in (( t i*2 n ) t m* ; )a mlloacll o( c2 () 2; ) ; ch = getche( ) ; } p p p 55 63 28 45 Memory Leaks ? p = malloc ( 2 ) ; **p( p= + p ie )r =; per ; printf ( ”Another student y/n” ) ;
- 5. Memory Leak? main( ) { int *j ; int *f( ) ; j 400 j = f( ) ; printf ( ”%d”, *j ) ; a 25 } Memory Leaks f( int ) * f( ) { int a = 25 ; return ( a ) ; } 400 & Dangling Pointer
- 6. 55 400 63 28 45 60 400 node Linked List 750 750 900 200 900 120 NNUULLLL 120 55 63 28 45 60 NNUULLLL data link Best...
- 7. main( ) { struct node { p q r s 55 63 28 45 N int data ; struct node *link ; } ; struct node *p, *q, *r, *s ; malloc p = mallosciz ( (e soifz e( osft r(u scttr uncotd neo )de ) ; ) ) ; q = ( struct node * ) malloc ( sizeof ( struct node ) ) ; r = . . . s = . . . p data = 55 ;q data = 63 ; r data = 28 ; s data = 45 ; p link = q ; q link = r ; r link = s ; s link = NULL ; CCoonntt...... s Linked List ( struct node * ) malloc ( sizeof ( struct node ) ) ;
- 8. ....CCoonntt p q r s # include ”alloc.h” main( ) { ... ... ... ... s 55 63 28 45 N t t t printf ( ”%d %d %d %d”, p data, q data, r data, s data ) ; printf ( ”%d %d %d”, p data, p link data, p link link data ) ; t = p ; while ( t ! = N U L L ) { printf ( ”%d”, t data ) ; t = t link ; } }
- 9. # include ”alloc.h” struct node { int per ; struct node *link ; } ; main( ) { struct node *p ; char ch = ’Y’ ; int pp ; p = NULL ; while ( ch == ’Y’ ) { scanf ( ”%d %d %d”, m1, m2, m3 ) ; pp = ( m1 + m2 + m3 ) / 3 ; add ( ) ; printf ( ”Another student y/n” ) ; } ch = getche( ) ; } pp Most General
- 10. # include ”alloc.h” struct node { int per ; struct node *link ; } ; main( ) { struct node *p ; char ch = ’Y’ ; int pp ; p = NULL ; while ( ch == ’Y’ ) { scanf ( ”%d %d %d”, m1, m2, m3 ) ; pp = ( m1 + m2 + m3 ) / 3 ; add ( ) ; printf ( ”Another student y/n” ) ; } ch = getche( ) ; } pp Most General