Variable declarations at top of function,
separate from initialization.

Use == 0 instead of ! for checking pointers.

Consistent spacing around {, *, casts.

Declare 0-parameter functions as (void) not ().

Integer valued functions return -1 on failure, 0 on success.

do not keep sorted contiguous free list

fix bug in test code of malloc

test malloc

nit in sbrk
indirect block
fix dup to share fd struct