diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9e5ed38..488606d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -125,6 +125,7 @@ set(SOURCES
   src/libc/stdlib/atoll.c
   src/libc/stdlib/calloc.c
   src/libc/stdlib/div.c
+  src/libc/stdlib/exit.c
   src/libc/stdlib/labs.c
   src/libc/stdlib/ldiv.c
   src/libc/stdlib/llabs.c
diff --git a/STATUS b/STATUS
index 6109988..4a7db56 100644
--- a/STATUS
+++ b/STATUS
@@ -102,7 +102,12 @@ DONE:       Function/symbol/macro is defined, builds, links, and is tested
      7.20.1.4  strtol, strtoul, strtoll, strtoull: DONE
 !    7.20.2  Pseudo-random sequence generation functions: TODO
 !    7.20.3  Memory management functions: TODO (check existing code first)
-!    7.20.4  Communication with the environment: TODO
+!    7.20.4.1  abort: BDEPS(raise)
+!    7.20.4.2  atexit: TODO
+     7.20.4.3  exit: DONE       (missing stream flushing/closing/etc)
+     7.20.4.4  _Exit: DONE      (gint only)
+!    7.20.4.5  getenv: TODO
+!    7.20.4.6  system: TODO
 !    7.20.5  Searching and sorting utilities: TODO
      7.20.6.1  abs, labs, llabs: DONE
      7.20.6.2  div, ldiv, lldiv: DONE
diff --git a/include/stdlib.h b/include/stdlib.h
index 37ad1c8..d13e30b 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -3,6 +3,7 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include <bits/exit.h>
 
 /* Dynamic memory management. */
 
@@ -27,6 +28,14 @@ extern void *reallocarray(void *__ptr, size_t __nmemb, size_t __size);
 /* Free a block allocated by `malloc', `realloc' or `calloc'. */
 extern void free(void *__ptr);
 
+/* Communication with the environment. */
+
+/* Exit; calls handlers, flushes and closes streams and temporary files. */
+void exit(int __status);
+
+/* Exit immediately, bypassing exit handlers or signal handlers. */
+void _Exit(int __status);
+
 /* Integer arithmetic functions. */
 
 extern int abs(int __j);
diff --git a/include/target/casiowin-cg/bits/exit.h b/include/target/casiowin-cg/bits/exit.h
new file mode 100644
index 0000000..30e4207
--- /dev/null
+++ b/include/target/casiowin-cg/bits/exit.h
@@ -0,0 +1,8 @@
+#ifndef __BITS_EXIT_H__
+# define __BITS_EXIT_H__
+
+/* Exit codes for CASIOWIN add-ins. */
+#define EXIT_SUCCESS 1
+#define EXIT_FAILURE 0
+
+#endif /*__BITS_EXIT_H__*/
diff --git a/include/target/casiowin-fx/bits/exit.h b/include/target/casiowin-fx/bits/exit.h
new file mode 100644
index 0000000..30e4207
--- /dev/null
+++ b/include/target/casiowin-fx/bits/exit.h
@@ -0,0 +1,8 @@
+#ifndef __BITS_EXIT_H__
+# define __BITS_EXIT_H__
+
+/* Exit codes for CASIOWIN add-ins. */
+#define EXIT_SUCCESS 1
+#define EXIT_FAILURE 0
+
+#endif /*__BITS_EXIT_H__*/
diff --git a/include/target/gint/bits/exit.h b/include/target/gint/bits/exit.h
new file mode 100644
index 0000000..30e4207
--- /dev/null
+++ b/include/target/gint/bits/exit.h
@@ -0,0 +1,8 @@
+#ifndef __BITS_EXIT_H__
+# define __BITS_EXIT_H__
+
+/* Exit codes for CASIOWIN add-ins. */
+#define EXIT_SUCCESS 1
+#define EXIT_FAILURE 0
+
+#endif /*__BITS_EXIT_H__*/
diff --git a/include/target/vhex-generic/bits/exit.h b/include/target/vhex-generic/bits/exit.h
new file mode 100644
index 0000000..f2e1124
--- /dev/null
+++ b/include/target/vhex-generic/bits/exit.h
@@ -0,0 +1,7 @@
+#ifndef __BITS_EXIT_H__
+# define __BITS_EXIT_H__
+
+#define EXIT_SUCCESS 0
+#define EXIT_FAILURE 1
+
+#endif /*__BITS_EXIT_H__*/
diff --git a/src/libc/stdlib/abort.c b/src/libc/stdlib/abort.c
new file mode 100644
index 0000000..2191df9
--- /dev/null
+++ b/src/libc/stdlib/abort.c
@@ -0,0 +1,10 @@
+#include <stdlib.h>
+#include <bits/stdlib.h>
+
+void abort(int rc)
+{
+	/* TODO: Close BFile handles (essential) */
+
+	raise(SIGABRT);
+	_Exit(EXIT_FAILURE);
+}
diff --git a/src/libc/stdlib/exit.c b/src/libc/stdlib/exit.c
new file mode 100644
index 0000000..596a48a
--- /dev/null
+++ b/src/libc/stdlib/exit.c
@@ -0,0 +1,11 @@
+#include <stdlib.h>
+
+void exit(int rc)
+{
+	/* TODO: invoke atexit callbacks */
+	/* TODO: exit: Flush all streams */
+	/* TODO: exit: Close all streams */
+	/* TODO: exit: Remove temporary files */
+
+	_Exit(rc);
+}