DaniWeb Forum Index > Software Development > C

؟questions?

Please support our C advertiser: Programming Forums - DaniWeb Sister Site

Thread Solved

•

Join Date: May 2008

Posts: 10

Reputation: xlx16 is an unknown quantity at this point

Solved Threads: 0

xlx16

Offline

Newbie Poster

؟questions?

Dec 6th, 2008

hello again
i have three questions again:
how can i use malloc or calloc for a two demontional arrays?

is it true that A. calloc allocates memory in contiguous bytes, malloc does not ensure contiguous memory allocation?

the third question which is a bit irrelevent to programming
how memorey locations in computers are given address?i mean early intell CPUs could
onley address (64K) but what about the rest of memory locations?

thanks

•

Join Date: Dec 2005

Posts: 5,850

Reputation: Salem has a reputation beyond repute

Solved Threads: 751

Salem

Offline

Void main'ers are DOOMed

Re: ؟questions?

Dec 6th, 2008

> is it true that A. calloc allocates memory in contiguous bytes, malloc does not ensure contiguous memory allocation?
No, it's false.
calloc is nothing more than malloc + memset to wipe the memory to all-bits-zero.

> i mean early intell CPUs could onley address (64K)
Only 64K in a single block.
If you wanted more, then you had to start messing about with segment registers
http://en.wikipedia.org/wiki/X86

> how can i use malloc or calloc for a two demontional arrays?
One (of several) ways

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
char **arr = malloc( rows * sizeof *arr );
for ( r = 0 ; r < rows ; r++ ) {
    arr[r] = malloc( cols * sizeof *arr[r] );
}
char **arr = malloc( rows * sizeof *arr );
for ( r = 0 ; r < rows ; r++ ) {
    arr[r] = malloc( cols * sizeof *arr[r] );
}