I see at least three problems (without running it): 
1. f is never initialized to zero 
2. 102400? 1024000? Huh? 
3. Quite possibly, in a modern virtual memory based operating system, malloc will not return NULL when running out of physical and/or swap memory. It might return NULL when running out of virtual memory in the process adress space. 

Linux's man page for malloc says: 
"By default, Linux follows an optimistic memory allocation strategy. This means that when malloc() returns non-NULL there is no guarantee that the memory really is available. This is a really bad bug. In case it turns out that the system is out of memory, one or more processes will be killed by the infamous OOM killer." 

OOM killer kills random memory-heavy processes. Not good on a production system. OTOH, the author only said something about a generic UNIX system, not Linux... but probably system performance will at least be severely affected in most circumstances where no per-process limits are set. 

Sebastian

 Sebastian:

"By default, Linux follows an optimistic memory allocation strategy. This means that when malloc() returns non-NULL there is no guarantee that the memory really is available. This is a really bad bug. In case it turns out that the system is out of memory, one or more processes will be killed by the infamous OOM killer."

See, I told you Linux can't be counted on for production systems!