diff --git a/ueforth/common/opcodes.h b/ueforth/common/opcodes.h
index 48e4946..f0e03fa 100644
--- a/ueforth/common/opcodes.h
+++ b/ueforth/common/opcodes.h
@@ -35,8 +35,10 @@ typedef uint64_t udcell_t;
   X("OVER", OP_OVER, DUP; tos = sp[-1]) \
   X("DROP", OP_DROP, DROP) \
   X("@", OP_AT, tos = *(cell_t *) tos) \
+  X("L@", OP_LAT, tos = *(int32_t *) tos) \
   X("C@", OP_CAT, tos = *(uint8_t *) tos) \
   X("!", OP_STORE, *(cell_t *) tos = *sp; --sp; DROP) \
+  X("L!", OP_LSTORE, *(int32_t *) tos = *sp; --sp; DROP) \
   X("C!", OP_CSTORE, *(uint8_t *) tos = *sp; --sp; DROP) \
   X("FILL", OP_FILL, memset((void *) sp[-1], tos, *sp); sp -= 2; DROP) \
   X("MOVE", OP_MOVE, memmove((void *) sp[-1], (void *) *sp, tos); sp -= 2; DROP) \
diff --git a/ueforth/plan.txt b/ueforth/plan.txt
index 1c9bff6..a815e03 100644
--- a/ueforth/plan.txt
+++ b/ueforth/plan.txt
@@ -47,7 +47,7 @@ CORE
 0= 0< + UM/MOD */MOD 
 AND OR XOR
 DUP SWAP OVER DROP
-@ C@ ! C! FILL MOVE
+@ L@ C@ ! L! C! FILL MOVE
 SP@ SP! RP@ RP! >R R> R@
 EXECUTE BRANCH 0BRANCH DONEXT DOLIT
 ALITERAL CELL
diff --git a/ueforth/posix/posix.fs b/ueforth/posix/posix.fs
index 17d39bf..2860d44 100644
--- a/ueforth/posix/posix.fs
+++ b/ueforth/posix/posix.fs
@@ -21,6 +21,12 @@ z" write" 3 sysfunc write
 z" lseek" 3 sysfunc lseek
 z" exit" 1 sysfunc sysexit
 z" fork" 0 sysfunc fork
+z" mmap" 6 sysfunc mmap
+z" munmap" 2 sysfunc munmap
+
+( Errno )
+z" __errno_location" 0 sysfunc __errno_location
+: errno ( -- n ) __errno_location l@ ;
 
 ( Default Pipes )
 0 constant stdin
@@ -56,3 +62,13 @@ z" fork" 0 sysfunc fork
 : posix-bye   0 sysexit ;
 ' posix-bye is bye
 
+( I/O Error Helpers )
+: 0ior ( n -- n ior ) dup 0= if errno else 0 then ;
+
+( Words with OS assist )
+z" malloc" 1 sysfunc malloc
+z" free" 1 sysfunc sysfree
+z" realloc" 2 sysfunc realloc
+: allocate ( n -- a ior ) malloc 0ior ;
+: free ( a -- ior ) sysfree 0 ;
+: resize ( a n -- a ior ) realloc 0ior ;