diff --git a/sched/env_findvar.c b/sched/env_findvar.c
index 2ed10aede41..b789a101d0a 100644
--- a/sched/env_findvar.c
+++ b/sched/env_findvar.c
@@ -41,6 +41,7 @@
 
 #ifndef CONFIG_DISABLE_ENVIRON
 
+#include <stdbool.h>
 #include <string.h>
 #include <sched.h>
 
@@ -56,7 +57,7 @@
  * Function: env_cmpname
  ****************************************************************************/
 
-static boolean env_cmpname(const char *pszname, const char *peqname)
+static bool env_cmpname(const char *pszname, const char *peqname)
 {
   /* Search until we find anything different in the two names */
 
@@ -66,9 +67,9 @@ static boolean env_cmpname(const char *pszname, const char *peqname)
 
   if ( *pszname == '\0' && *peqname == '=' )
     {
-      return TRUE;
+      return true;
     }
-  return FALSE;
+  return false;
 }
 
 /****************************************************************************
diff --git a/sched/mq_internal.h b/sched/mq_internal.h
index 6a40144d401..e362ec2fbd4 100644
--- a/sched/mq_internal.h
+++ b/sched/mq_internal.h
@@ -45,6 +45,7 @@
 
 #include <sys/types.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <limits.h>
 #include <mqueue.h>
 #include <sched.h>
@@ -114,7 +115,7 @@ struct msgq_s
   int16_t      nwaitnotfull;  /* Number tasks waiting for not full */
   int16_t      nwaitnotempty; /* Number tasks waiting for not empty */
   uint8_t      maxmsgsize;    /* Max size of message in message queue */
-  boolean      unlinked;      /* TRUE if the msg queue has been unlinked */
+  bool         unlinked;      /* true if the msg queue has been unlinked */
 #ifndef CONFIG_DISABLE_SIGNALS
   FAR struct mq_des *ntmqdes; /* Notification: Owning mqdes (NULL if none) */
   pid_t        ntpid;         /* Notification: Receiving Task's PID */
diff --git a/sched/mq_receive.c b/sched/mq_receive.c
index cd7748c3f37..aff9e3be88f 100644
--- a/sched/mq_receive.c
+++ b/sched/mq_receive.c
@@ -38,15 +38,18 @@
  ************************************************************************/
 
 #include <nuttx/config.h>
+
 #include <sys/types.h>
+#include <stdbool.h>
 #include <errno.h>
 #include <mqueue.h>
 #include <debug.h>
 #include <nuttx/arch.h>
+
 #include "mq_internal.h"
 
 /************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ************************************************************************/
 
 /************************************************************************
@@ -119,7 +122,7 @@ ssize_t mq_receive(mqd_t mqdes, void *msg, size_t msglen, int *prio)
   irqstate_t   saved_state;
   ssize_t      ret = ERROR;
 
-  DEBUGASSERT(up_interrupt_context() == FALSE);
+  DEBUGASSERT(up_interrupt_context() == false);
 
   /* Verify the input parameters and, in case of an error, set
    * errno appropriately.
diff --git a/sched/mq_timedreceive.c b/sched/mq_timedreceive.c
index a13a8a632e7..1100331eb85 100644
--- a/sched/mq_timedreceive.c
+++ b/sched/mq_timedreceive.c
@@ -41,6 +41,7 @@
 
 #include <sys/types.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <unistd.h>
 #include <errno.h>
 #include <mqueue.h>
@@ -53,7 +54,7 @@
 #include "mq_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -196,7 +197,7 @@ ssize_t mq_timedreceive(mqd_t mqdes, void *msg, size_t msglen,
   irqstate_t   saved_state;
   int          ret = ERROR;
 
-  DEBUGASSERT(up_interrupt_context() == FALSE);
+  DEBUGASSERT(up_interrupt_context() == false);
 
   /* Verify the input parameters and, in case of an error, set
    * errno appropriately.
diff --git a/sched/mq_timedsend.c b/sched/mq_timedsend.c
index 7bdbbb7e1da..412d2b8b471 100644
--- a/sched/mq_timedsend.c
+++ b/sched/mq_timedsend.c
@@ -41,6 +41,7 @@
 
 #include <sys/types.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <unistd.h>
 #include <mqueue.h>
 #include <wdog.h>
@@ -53,7 +54,7 @@
 #include "mq_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -192,7 +193,7 @@ int mq_timedsend(mqd_t mqdes, const char *msg, size_t msglen, int prio,
   irqstate_t   saved_state;
   int          ret = ERROR;
 
-  DEBUGASSERT(up_interrupt_context() == FALSE);
+  DEBUGASSERT(up_interrupt_context() == false);
 
   /* Verify the input parameters -- setting errno appropriately
    * on any failures to verify.
diff --git a/sched/mq_unlink.c b/sched/mq_unlink.c
index 7d77e266d67..0f1e63e4884 100644
--- a/sched/mq_unlink.c
+++ b/sched/mq_unlink.c
@@ -39,13 +39,15 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <mqueue.h>
 #include <sched.h>
+
 #include "os_internal.h"
 #include "mq_internal.h"
 
 /************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ************************************************************************/
 
 /************************************************************************
@@ -131,7 +133,7 @@ int mq_unlink(const char *mq_name)
 
           else
             {
-              msgq->unlinked = TRUE;
+              msgq->unlinked = true;
             }
 
           ret = OK;
diff --git a/sched/os_internal.h b/sched/os_internal.h
index cda7dc61ceb..d37000b6a53 100644
--- a/sched/os_internal.h
+++ b/sched/os_internal.h
@@ -41,13 +41,15 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
+
 #include <sys/types.h>
+#include <stdbool.h>
 #include <queue.h>
 #include <sched.h>
 #include <nuttx/kmalloc.h>
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /* OS CRASH CODES */
@@ -136,7 +138,7 @@ typedef struct pidhash_s  pidhash_t;
 struct tasklist_s
 {
   DSEG volatile dq_queue_t *list; /* Pointer to the task list */
-  boolean prioritized;            /* TRUE if the list is prioritized */
+  bool prioritized;               /* true if the list is prioritized */
 };
 typedef struct tasklist_s tasklist_t;
 
@@ -240,41 +242,39 @@ extern const tasklist_t g_tasklisttable[NUM_TASK_STATES];
  * Public Function Prototypes
  ****************************************************************************/
 
-extern void    task_start(void);
-extern int     task_schedsetup(FAR _TCB *tcb, int priority,
-                               start_t start, main_t main);
-extern int     task_argsetup(FAR _TCB *tcb, const char *name,
-                             const char *argv[]);
-extern int     task_deletecurrent(void);
+extern void task_start(void);
+extern int  task_schedsetup(FAR _TCB *tcb, int priority, start_t start,
+                            main_t main);
+extern int  task_argsetup(FAR _TCB *tcb, const char *name, const char *argv[]);
+extern int  task_deletecurrent(void);
 
-extern boolean sched_addreadytorun(FAR _TCB *rtrtcb);
-extern boolean sched_removereadytorun(FAR _TCB *rtrtcb);
-extern boolean sched_addprioritized(FAR _TCB *newTcb,
-                                    DSEG dq_queue_t *list);
-extern boolean sched_mergepending(void);
-extern void    sched_addblocked(FAR _TCB *btcb, tstate_t task_state);
-extern void    sched_removeblocked(FAR _TCB *btcb);
-extern int     sched_setpriority(FAR _TCB *tcb, int sched_priority);
+extern bool sched_addreadytorun(FAR _TCB *rtrtcb);
+extern bool sched_removereadytorun(FAR _TCB *rtrtcb);
+extern bool sched_addprioritized(FAR _TCB *newTcb, DSEG dq_queue_t *list);
+extern bool sched_mergepending(void);
+extern void sched_addblocked(FAR _TCB *btcb, tstate_t task_state);
+extern void sched_removeblocked(FAR _TCB *btcb);
+extern int  sched_setpriority(FAR _TCB *tcb, int sched_priority);
 #ifdef CONFIG_PRIORITY_INHERITANCE
-extern int     sched_reprioritize(FAR _TCB *tcb, int sched_priority);
+extern int  sched_reprioritize(FAR _TCB *tcb, int sched_priority);
 #else
 #  define sched_reprioritize(tcb,sched_priority) sched_setpriority(tcb,sched_priority)
 #endif
 extern FAR _TCB *sched_gettcb(pid_t pid);
-extern boolean sched_verifytcb(FAR _TCB *tcb);
+extern bool sched_verifytcb(FAR _TCB *tcb);
 
 #if CONFIG_NFILE_DESCRIPTORS > 0 || CONFIG_NSOCKET_DESCRIPTORS > 0
-extern int     sched_setupidlefiles(FAR _TCB *tcb);
-extern int     sched_setuptaskfiles(FAR _TCB *tcb);
-extern int     sched_setuppthreadfiles(FAR _TCB *tcb);
+extern int  sched_setupidlefiles(FAR _TCB *tcb);
+extern int  sched_setuptaskfiles(FAR _TCB *tcb);
+extern int  sched_setuppthreadfiles(FAR _TCB *tcb);
 #if CONFIG_NFILE_DESCRIPTORS > 0 && CONFIG_NFILE_STREAMS > 0
-extern int     sched_setupstreams(FAR _TCB *tcb);
-extern int     sched_flushfiles(FAR _TCB *tcb);
+extern int  sched_setupstreams(FAR _TCB *tcb);
+extern int  sched_flushfiles(FAR _TCB *tcb);
 #endif
-extern int     sched_releasefiles(FAR _TCB *tcb);
+extern int  sched_releasefiles(FAR _TCB *tcb);
 #endif
 
-extern int     sched_releasetcb(FAR _TCB *tcb);
-extern void    sched_garbagecollection(void);
+extern int  sched_releasetcb(FAR _TCB *tcb);
+extern void sched_garbagecollection(void);
 
 #endif /* __OS_INTERNAL_H */
diff --git a/sched/os_start.c b/sched/os_start.c
index 6f36f58a625..3c25b7008cb 100644
--- a/sched/os_start.c
+++ b/sched/os_start.c
@@ -38,6 +38,7 @@
  ****************************************************************************/
 
 #include  <sys/types.h>
+#include  <stdbool.h>
 #include  <debug.h>
 #include  <string.h>
 
@@ -66,7 +67,7 @@
 #endif
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -174,18 +175,18 @@ pid_t g_worker;
 
 const tasklist_t g_tasklisttable[NUM_TASK_STATES] =
 {
-  { NULL,                    FALSE },  /* TSTATE_TASK_INVALID */
-  { &g_pendingtasks,         TRUE  },  /* TSTATE_TASK_PENDING */
-  { &g_readytorun,           TRUE  },  /* TSTATE_TASK_READYTORUN */
-  { &g_readytorun,           TRUE  },  /* TSTATE_TASK_RUNNING */
-  { &g_inactivetasks,        FALSE },  /* TSTATE_TASK_INACTIVE */
-  { &g_waitingforsemaphore,  TRUE  },  /* TSTATE_WAIT_SEM */
+  { NULL,                    false },  /* TSTATE_TASK_INVALID */
+  { &g_pendingtasks,         true  },  /* TSTATE_TASK_PENDING */
+  { &g_readytorun,           true  },  /* TSTATE_TASK_READYTORUN */
+  { &g_readytorun,           true  },  /* TSTATE_TASK_RUNNING */
+  { &g_inactivetasks,        false },  /* TSTATE_TASK_INACTIVE */
+  { &g_waitingforsemaphore,  true  },  /* TSTATE_WAIT_SEM */
 #ifndef CONFIG_DISABLE_SIGNALS
-  { &g_waitingforsignal,     FALSE },  /* TSTATE_WAIT_SIG */
+  { &g_waitingforsignal,     false },  /* TSTATE_WAIT_SIG */
 #endif
 #ifndef CONFIG_DISABLE_MQUEUE
-  { &g_waitingformqnotempty, TRUE  },  /* TSTATE_WAIT_MQNOTEMPTY */
-  { &g_waitingformqnotfull,  TRUE  }   /* TSTATE_WAIT_MQNOTFULL */
+  { &g_waitingformqnotempty, true  },  /* TSTATE_WAIT_MQNOTEMPTY */
+  { &g_waitingformqnotfull,  true  }   /* TSTATE_WAIT_MQNOTFULL */
 #endif
 };
 
diff --git a/sched/pthread_completejoin.c b/sched/pthread_completejoin.c
index fa91e4a6a43..fff3b46cf25 100644
--- a/sched/pthread_completejoin.c
+++ b/sched/pthread_completejoin.c
@@ -37,15 +37,19 @@
  * Included Files
  ************************************************************************/
 
+#include <nuttx/config.h>
+
 #include <sys/types.h>
+#include <stdbool.h>
 #include <pthread.h>
 #include <errno.h>
 #include <debug.h>
+
 #include "os_internal.h"
 #include "pthread_internal.h"
 
 /************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ************************************************************************/
 
 /************************************************************************
@@ -74,7 +78,7 @@
  *
  ************************************************************************/
 
-static boolean pthread_notifywaiters(FAR join_t *pjoin)
+static bool pthread_notifywaiters(FAR join_t *pjoin)
 {
   int ntasks_waiting;
   int status;
@@ -111,9 +115,9 @@ static boolean pthread_notifywaiters(FAR join_t *pjoin)
        */
 
       (void)pthread_takesemaphore(&pjoin->data_sem);
-      return TRUE;
+      return true;
     }
-  return FALSE;
+  return false;
 }
 
 /************************************************************************
@@ -158,11 +162,11 @@ int pthread_completejoin(pid_t pid, FAR void *exit_value)
     }
   else
     {
-      boolean waiters;
+      bool waiters;
 
       /* Save the return exit value in the thread structure. */
 
-      pjoin->terminated = TRUE;
+      pjoin->terminated = true;
       pjoin->exit_value = exit_value;
 
       /* Notify waiters of the availability of the exit value */
diff --git a/sched/pthread_create.c b/sched/pthread_create.c
index 4f3d05bdc1c..b49698122a4 100644
--- a/sched/pthread_create.c
+++ b/sched/pthread_create.c
@@ -38,7 +38,9 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
+
 #include <sys/types.h>
+#include <stdbool.h>
 #include <string.h>
 #include <pthread.h>
 #include <sched.h>
@@ -47,13 +49,14 @@
 #include <queue.h>
 #include <nuttx/kmalloc.h>
 #include <nuttx/arch.h>
+
 #include "os_internal.h"
 #include "clock_internal.h"
 #include "env_internal.h"
 #include "pthread_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -204,7 +207,7 @@ static void pthread_start(void)
 
   /* Report to the spawner that we successfully started. */
 
-  pjoin->started = TRUE;
+  pjoin->started = true;
   (void)pthread_givesemaphore(&pjoin->data_sem);
 
   /* Pass control to the thread entry point.  The argument is
diff --git a/sched/pthread_detach.c b/sched/pthread_detach.c
index dc835293030..52ea63ca538 100644
--- a/sched/pthread_detach.c
+++ b/sched/pthread_detach.c
@@ -40,6 +40,7 @@
 #include <nuttx/config.h>
 
 #include <sys/types.h>
+#include <stdbool.h>
 #include <pthread.h>
 #include <errno.h>
 #include <debug.h>
@@ -48,7 +49,7 @@
 #include "pthread_internal.h"
 
 /************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ************************************************************************/
 
 /************************************************************************
@@ -121,7 +122,7 @@ int pthread_detach(pthread_t thread)
            * thread exits
            */
 
-          pjoin->detached = TRUE;
+          pjoin->detached = true;
         }
 
       /* Either case is successful */
diff --git a/sched/pthread_internal.h b/sched/pthread_internal.h
index 55d58d49f2f..1770ff1b50a 100644
--- a/sched/pthread_internal.h
+++ b/sched/pthread_internal.h
@@ -40,13 +40,16 @@
  * Included Files
  ****************************************************************************/
 
+#include <nuttx/config.h>
+
 #include <sys/types.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <pthread.h>
 #include <nuttx/compiler.h>
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -66,9 +69,9 @@ struct join_s
 {
   FAR struct join_s *next;       /* Implements link list */
   uint8_t        crefs;          /* Reference count */
-  boolean        started;        /* TRUE: pthread started. */
-  boolean        detached;       /* TRUE: pthread_detached'ed */
-  boolean        terminated;     /* TRUE: detach'ed+exit'ed */
+  bool           started;        /* true: pthread started. */
+  bool           detached;       /* true: pthread_detached'ed */
+  bool           terminated;     /* true: detach'ed+exit'ed */
   pthread_t      thread;         /* Includes pid */
   sem_t          exit_sem;       /* Implements join */
   sem_t          data_sem;       /* Implements join */
diff --git a/sched/pthread_once.c b/sched/pthread_once.c
index b2db0ab5f4e..dc0fcd2bd7b 100644
--- a/sched/pthread_once.c
+++ b/sched/pthread_once.c
@@ -39,13 +39,14 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <pthread.h>
 #include <sched.h>
 #include <errno.h>
 #include <debug.h>
 
 /********************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ********************************************************************************/
 
 /********************************************************************************
@@ -104,7 +105,7 @@ int pthread_once(FAR pthread_once_t *once_control, CODE void (*init_routine)(voi
       sched_lock();
       if (!*once_control)
         {
-          *once_control = TRUE;
+          *once_control = true;
 
           /* Call the init_routine with pre-emption enabled. */
 
diff --git a/sched/sched_addprioritized.c b/sched/sched_addprioritized.c
index 824dc32d651..d937dcee3ed 100644
--- a/sched/sched_addprioritized.c
+++ b/sched/sched_addprioritized.c
@@ -40,13 +40,14 @@
 #include <nuttx/config.h>
 
 #include <stdint.h>
+#include <stdbool.h>
 #include <queue.h>
 #include <assert.h>
 
 #include "os_internal.h"
 
 /************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ************************************************************************/
 
 /************************************************************************
@@ -80,7 +81,7 @@
  *   list - Points to the prioritized list to add tcb to
  *
  * Return Value:
- *   TRUE if the head of the list has changed.
+ *   true if the head of the list has changed.
  *
  * Assumptions:
  * - The caller has established a critical section before
@@ -94,12 +95,12 @@
  *   match the state associated with the list.
  ************************************************************************/
 
-boolean sched_addprioritized(FAR _TCB *tcb, DSEG dq_queue_t *list)
+bool sched_addprioritized(FAR _TCB *tcb, DSEG dq_queue_t *list)
 {
   FAR _TCB *next;
   FAR _TCB *prev;
   uint8_t sched_priority = tcb->sched_priority;
-  boolean ret = FALSE;
+  bool ret = false;
 
   /* Lets do a sanity check before we get started. */
 
@@ -131,7 +132,7 @@ boolean sched_addprioritized(FAR _TCB *tcb, DSEG dq_queue_t *list)
           tcb->blink = NULL;
           list->head = (FAR dq_entry_t*)tcb;
           list->tail = (FAR dq_entry_t*)tcb;
-          ret = TRUE;
+          ret = true;
         }
       else
         {
@@ -156,7 +157,7 @@ boolean sched_addprioritized(FAR _TCB *tcb, DSEG dq_queue_t *list)
           tcb->blink  = NULL;
           next->blink = tcb;
           list->head  = (FAR dq_entry_t*)tcb;
-          ret = TRUE;
+          ret = true;
         }
       else
         {
diff --git a/sched/sched_addreadytorun.c b/sched/sched_addreadytorun.c
index 503d15f985e..51e219342b5 100644
--- a/sched/sched_addreadytorun.c
+++ b/sched/sched_addreadytorun.c
@@ -39,13 +39,14 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <queue.h>
 #include <assert.h>
 
 #include "os_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -83,7 +84,7 @@
  *   btcb - Points to the blocked TCB that is ready-to-run
  *
  * Return Value:
- *   TRUE if the currently active task (the head of the 
+ *   true if the currently active task (the head of the 
  *     g_readytorun list) has changed.
  *
  * Assumptions:
@@ -97,10 +98,10 @@
  *
  ****************************************************************************/
 
-boolean sched_addreadytorun(FAR _TCB *btcb)
+bool sched_addreadytorun(FAR _TCB *btcb)
 {
   FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
-  boolean ret;
+  bool ret;
 
   /* Check if pre-emption is disabled for the current running
    * task and if the new ready-to-run task  would cause the
@@ -115,7 +116,7 @@ boolean sched_addreadytorun(FAR _TCB *btcb)
 
       sched_addprioritized(btcb, (FAR dq_queue_t*)&g_pendingtasks);
       btcb->task_state = TSTATE_TASK_PENDING;
-      ret = FALSE;
+      ret = false;
     }
 
   /* Otherwise, add the new task to the g_readytorun task list */
@@ -134,14 +135,14 @@ boolean sched_addreadytorun(FAR _TCB *btcb)
 
       btcb->task_state = TSTATE_TASK_RUNNING;
       btcb->flink->task_state = TSTATE_TASK_READYTORUN;
-      ret = TRUE;
+      ret = true;
     }
   else
     {
       /* The new btcb was added in the middle of the g_readytorun list */
 
       btcb->task_state = TSTATE_TASK_READYTORUN;
-      ret = FALSE;
+      ret = false;
     }
 
   return ret;
diff --git a/sched/sched_mergepending.c b/sched/sched_mergepending.c
index c45010e8c03..1448c009610 100644
--- a/sched/sched_mergepending.c
+++ b/sched/sched_mergepending.c
@@ -39,13 +39,14 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <queue.h>
 #include <assert.h>
 
 #include "os_internal.h"
 
 /************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ************************************************************************/
 
 /************************************************************************
@@ -79,7 +80,7 @@
  *   None
  *
  * Return Value:
- *   TRUE if the head of the g_readytorun task list has changed.
+ *   true if the head of the g_readytorun task list has changed.
  *
  * Assumptions:
  * - The caller has established a critical section before
@@ -90,13 +91,13 @@
  *
  ************************************************************************/
 
-boolean sched_mergepending(void)
+bool sched_mergepending(void)
 {
   FAR _TCB *pndtcb;
   FAR _TCB *pndnext;
   FAR _TCB *rtrtcb;
   FAR _TCB *rtrprev;
-  boolean ret = FALSE;
+  bool ret = false;
 
   /* Initialize the inner search loop */
 
@@ -142,7 +143,7 @@ boolean sched_mergepending(void)
               g_readytorun.head = (FAR dq_entry_t*)pndtcb;
               rtrtcb->task_state = TSTATE_TASK_READYTORUN;
               pndtcb->task_state = TSTATE_TASK_RUNNING;
-              ret = TRUE;
+              ret = true;
             }
           else
             {
diff --git a/sched/sched_removereadytorun.c b/sched/sched_removereadytorun.c
index f09b5fc9910..46f148150a7 100644
--- a/sched/sched_removereadytorun.c
+++ b/sched/sched_removereadytorun.c
@@ -39,13 +39,14 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <queue.h>
 #include <assert.h>
 
 #include "os_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -78,7 +79,7 @@
  *   rtcb - Points to the TCB that is ready-to-run
  *
  * Return Value:
- *   TRUE if the currently active task (the head of the 
+ *   true if the currently active task (the head of the 
  *     g_readytorun list) has changed.
  *
  * Assumptions:
@@ -87,11 +88,12 @@
  *   a good idea -- use irqsave()).
  * - The caller handles the condition that occurs if the
  *   the head of the g_readytorun list is changed.
+ *
  ****************************************************************************/
 
-boolean sched_removereadytorun(FAR _TCB *rtcb)
+bool sched_removereadytorun(FAR _TCB *rtcb)
 {
-  boolean ret = FALSE;
+  bool ret = false;
 
   /* Check if the TCB to be removed is at the head of the ready
    * to run list.  In this case, we are removing the currently
@@ -109,7 +111,7 @@ boolean sched_removereadytorun(FAR _TCB *rtcb)
       sched_note_switch(rtcb, rtcb->flink);
 
       rtcb->flink->task_state = TSTATE_TASK_RUNNING;
-      ret = TRUE;
+      ret = true;
     }
 
   /* Remove the TCB from the ready-to-run list */
diff --git a/sched/sched_verifytcb.c b/sched/sched_verifytcb.c
index 5b91e77d23e..af7cdebe14a 100644
--- a/sched/sched_verifytcb.c
+++ b/sched/sched_verifytcb.c
@@ -39,6 +39,7 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <sched.h>
 
 #include "os_internal.h"
@@ -71,12 +72,12 @@
  * Name: sched_verifytcb
  *
  * Description:
- *   Return TRUE if the tcb refers to an active task; FALSE if it is a stale
+ *   Return true if the tcb refers to an active task; false if it is a stale
  *   TCB handle.
  *
  ****************************************************************************/
 
-boolean sched_verifytcb(FAR _TCB *tcb)
+bool sched_verifytcb(FAR _TCB *tcb)
 {
   /* Return true if the PID hashes to this TCB. */
 
diff --git a/sched/sem_internal.h b/sched/sem_internal.h
index 054946301a1..feb99ef0b3d 100644
--- a/sched/sem_internal.h
+++ b/sched/sem_internal.h
@@ -44,12 +44,13 @@
 #include <nuttx/compiler.h>
 
 #include <stdint.h>
+#include <stdbool.h>
 #include <semaphore.h>
 #include <sched.h>
 #include <queue.h>
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -64,7 +65,7 @@ struct nsem_s
   FAR struct nsem_s *blink;     /* Backward link */
   uint16_t           nconnect;  /* Number of connections to semaphore */
   FAR char          *name;      /* Semaphore name (NULL if un-named) */
-  boolean            unlinked;  /* TRUE if the semaphore has been unlinked */
+  bool               unlinked;  /* true if the semaphore has been unlinked */
   sem_t              sem;       /* The semaphore itself */
 };
 typedef struct nsem_s nsem_t;
diff --git a/sched/sem_open.c b/sched/sem_open.c
index aeb5097eb28..cd9ca6129ab 100644
--- a/sched/sem_open.c
+++ b/sched/sem_open.c
@@ -37,7 +37,10 @@
  * Included Files
  ****************************************************************************/
 
+#include <nuttx/config.h>
+
 #include <sys/types.h>
+#include <stdbool.h>
 #include <stdarg.h>
 #include <limits.h>
 #include <fcntl.h>
@@ -48,7 +51,7 @@
 #include "sem_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -178,7 +181,7 @@ FAR sem_t *sem_open (FAR const char *name, int oflag, ...)
                       sem_init(sem, 0, value);
 
                       psem->nconnect = 1;
-                      psem->unlinked = FALSE;
+                      psem->unlinked = false;
                       psem->name = (FAR char*)psem + sizeof(nsem_t);
                       strcpy(psem->name, name);
 
diff --git a/sched/sem_trywait.c b/sched/sem_trywait.c
index 27eb6a60c86..d50dc106dda 100644
--- a/sched/sem_trywait.c
+++ b/sched/sem_trywait.c
@@ -39,6 +39,7 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <semaphore.h>
 #include <sched.h>
 #include <errno.h>
@@ -48,7 +49,7 @@
 #include "sem_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -102,7 +103,7 @@ int sem_trywait(FAR sem_t *sem)
 
   /* This API should not be called from interrupt handlers */
 
-  DEBUGASSERT(up_interrupt_context() == FALSE)
+  DEBUGASSERT(up_interrupt_context() == false)
 
   /* Assume any errors reported are due to invalid arguments. */
 
diff --git a/sched/sem_unlink.c b/sched/sem_unlink.c
index 79f8be0104f..ec08641803d 100644
--- a/sched/sem_unlink.c
+++ b/sched/sem_unlink.c
@@ -39,6 +39,7 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <semaphore.h>
 #include <sched.h>
 #include <queue.h>
@@ -47,7 +48,7 @@
 #include "sem_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -126,7 +127,7 @@ int sem_unlink(FAR const char *name)
 
           else
             {
-              psem->unlinked = TRUE;
+              psem->unlinked = true;
             }
           ret = OK;
         }
diff --git a/sched/sem_wait.c b/sched/sem_wait.c
index f723b721504..747d7cd48bb 100644
--- a/sched/sem_wait.c
+++ b/sched/sem_wait.c
@@ -39,6 +39,7 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <semaphore.h>
 #include <errno.h>
 #include <assert.h>
@@ -48,7 +49,7 @@
 #include "sem_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -101,7 +102,7 @@ int sem_wait(FAR sem_t *sem)
 
   /* This API should not be called from interrupt handlers */
 
-  DEBUGASSERT(up_interrupt_context() == FALSE)
+  DEBUGASSERT(up_interrupt_context() == false)
 
   /* Assume any errors reported are due to invalid arguments. */
 
diff --git a/sched/sig_ismember.c b/sched/sig_ismember.c
index 77cd520fd06..670ef7bd207 100644
--- a/sched/sig_ismember.c
+++ b/sched/sig_ismember.c
@@ -40,7 +40,7 @@
 #include <signal.h>
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -75,7 +75,7 @@
  *   signo - Signal to test for
  *
  * Return Value:
- *   1 (TRUE), if the specified signal is a member of the set,
+ *   1 (true), if the specified signal is a member of the set,
  *   0 (OK or FALSE), if it is not, or
  *  -1 (ERROR) if the signal number is invalid.
  *
diff --git a/sched/wd_cancel.c b/sched/wd_cancel.c
index f17e0d227c7..ea686cf92aa 100644
--- a/sched/wd_cancel.c
+++ b/sched/wd_cancel.c
@@ -39,6 +39,7 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <assert.h>
 #include <wdog.h>
 #include <nuttx/arch.h>
@@ -47,7 +48,7 @@
 #include "wd_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -156,7 +157,7 @@ int wd_cancel (WDOG_ID wdid)
 
       /* Mark the watchdog inactive */
 
-      wdid->active = FALSE;
+      wdid->active = false;
     }
   irqrestore(saved_state);
   return ret;
diff --git a/sched/wd_create.c b/sched/wd_create.c
index 296ff5c3dde..a383de6a5be 100644
--- a/sched/wd_create.c
+++ b/sched/wd_create.c
@@ -39,6 +39,7 @@
 
 #include <nuttx/config.h>
 
+#include <stdbool.h>
 #include <wdog.h>
 #include <queue.h>
 #include <nuttx/arch.h>
@@ -46,7 +47,7 @@
 #include "wd_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -101,7 +102,7 @@ WDOG_ID wd_create (void)
   if (wdog)
     {
       wdog->next = NULL;
-      wdog->active = FALSE;
+      wdog->active = false;
     }
   return (WDOG_ID)wdog;
 }
diff --git a/sched/wd_internal.h b/sched/wd_internal.h
index 2a64d9eafff..4df2a0e6576 100644
--- a/sched/wd_internal.h
+++ b/sched/wd_internal.h
@@ -43,11 +43,12 @@
 #include <nuttx/config.h>
 
 #include <stdint.h>
+#include <stdbool.h>
 #include <wdog.h>
 #include <nuttx/compiler.h>
 
 /************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ************************************************************************/
 
 /************************************************************************
@@ -66,7 +67,7 @@ struct wdog_s
   FAR void          *picbase;    /* PIC base address */
 #endif
   int                lag;        /* Timer associated with the delay */
-  boolean            active;     /* TRUE if the watchdog is actively timing */
+  bool               active;     /* true if the watchdog is actively timing */
   uint8_t            argc;       /* The number of parameters to pass */
   uint32_t           parm[CONFIG_MAX_WDOGPARMS];
 };
diff --git a/sched/wd_start.c b/sched/wd_start.c
index 31bc3bea0cc..1f37dbf99fd 100644
--- a/sched/wd_start.c
+++ b/sched/wd_start.c
@@ -40,6 +40,7 @@
 #include <sys/types.h>
 
 #include <stdint.h>
+#include <stdbool.h>
 #include <stdarg.h>
 #include <wdog.h>
 #include <unistd.h>
@@ -52,7 +53,7 @@
 #include "wd_internal.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -267,7 +268,7 @@ int wd_start(WDOG_ID wdog, int delay, wdentry_t wdentry,  int argc, ...)
   /* Put the lag into the watchdog structure and mark it as active. */
 
   wdog->lag = delay;
-  wdog->active = TRUE;
+  wdog->active = true;
 
   irqrestore(saved_state);
   return OK;
@@ -330,7 +331,7 @@ void wd_timer(void)
 
               /* Indicate that the watchdog is no longer active. */
 
-              wdog->active = FALSE;
+              wdog->active = false;
 
               /* Get the current task's process ID.  We'll need this later to
                * see if the watchdog function caused a context switch.