RTOS Key Words with Definitions

1. RTOS Keywords with Definitions
Comprehensive Overview for
Learning RTOS

2. RTOS (Real-Time Operating System)
• An operating system designed to process data
and events within a strict time deadline, used
in embedded and time-critical systems.

3. Task/Thread
• A basic unit of execution in RTOS. Multiple
tasks can run concurrently and independently.

4. Task Scheduling
• The method by which an RTOS decides the
order in which tasks are executed.

5. Preemptive Scheduling
• A scheduling method where the highest-
priority task is executed by interrupting the
currently running lower-priority task.

6. Cooperative Scheduling
• Tasks voluntarily give up control to allow other
tasks to run.

7. Context Switching
• The process of saving and loading task states
during switching between tasks.

8. Multitasking
• Running multiple tasks seemingly in parallel by
switching between them rapidly.

9. Priority
• A value assigned to tasks; higher-priority tasks
are executed before lower-priority ones.

10. Interrupt
• A signal that temporarily halts the CPU to
handle an event (e.g., I/O or timer).

11. ISR (Interrupt Service Routine)
• The function executed in response to an
interrupt.

12. Semaphore
• A signaling mechanism used for task
synchronization or resource management.

13. Mutex (Mutual Exclusion)
• A locking mechanism used to prevent multiple
tasks from accessing a shared resource
simultaneously.

14. Deadlock
• A condition where tasks wait indefinitely for
resources held by each other.

15. Starvation
• A task fails to get CPU time or resources
because higher-priority tasks keep running.

16. Latency
• The time taken by the system to respond to an
event.

17. Jitter
• Variation in response time to the same event
under the same conditions.

18. Kernel
• The core part of RTOS that manages task
scheduling, interrupts, and system resources.

19. Tick Timer
• A periodic timer interrupt used by the RTOS
scheduler to track time and manage
delays/timeouts.

20. Message Queue
• An RTOS service that enables tasks to send
and receive data/messages in a queued
manner.

21. Event Flags
• A synchronization mechanism where tasks
wait for a specific set of flags to be set.

22. Critical Section
• A code segment that must not be interrupted
to prevent data corruption.

23. Watchdog Timer
• A timer that resets the system if software fails
to operate correctly.

24. Real-Time Clock (RTC)
• A clock module used to keep track of the
current time in real-world terms.

25. Embedded System
• A dedicated system that performs a specific
function within a larger system, often with
real-time constraints.

26. Determinism
• The ability of the system to perform
operations within a known time frame.

27. Memory Management
• The process of managing memory allocation
and deallocation for tasks.

28. Thread-safe
• Describes code or functions that operate
correctly when multiple threads access them
simultaneously.

29. Spinlock
• A type of lock where the processor
continuously checks for the lock to become
available, wasting CPU cycles.

30. Idle Task
• A default low-priority task that runs when no
other tasks are ready to execute.

31. Task State
• The current status of a task (e.g., ready,
running, blocked, suspended).

32. Blocked State
• A task is waiting for an event or resource and
is not ready to run.

33. Ready State
• A task is ready to run but waiting for CPU
time.

34. Running State
• A task that is currently being executed by the
CPU.

35. Suspended State
• A task that is paused and will not run until
explicitly resumed.

36. Heap Memory
• Dynamically allocated memory during
runtime.

37. Stack Memory
• Memory used by tasks for function calls and
local variables.

38. Stack Overflow
• Occurs when a task uses more stack memory
than allocated, leading to unpredictable
behavior or crashes.

39. Inter-task Communication (ITC)
• Mechanisms for tasks to communicate and
synchronize (e.g., queues, semaphores, pipes).

40. Signal
• A notification or flag sent between tasks or
from an ISR to a task.

41. Scheduler
• The RTOS component that selects which task
to run based on scheduling policy.

42. Round Robin Scheduling
• Each task gets an equal time slice to execute in
a cyclic order.

43. Time Slice
• A fixed amount of time given to a task in
round-robin scheduling.

44. Dynamic Priority
• Task priorities that can change at runtime
based on system conditions.

45. Static Priority
• Priorities assigned at compile time and do not
change during execution.

46. Rate Monotonic Scheduling (RMS)
• A fixed-priority scheduling algorithm where
shorter period tasks have higher priority.

47. Earliest Deadline First (EDF)
• A dynamic scheduling algorithm where the
task with the closest deadline is scheduled
first.

48. Hard Real-Time System
• A system where missing a deadline is
considered a total system failure.

49. Soft Real-Time System
• A system where deadline misses are tolerable
but degrade performance.

50. Memory Protection Unit (MPU)
• Hardware that restricts access to certain
memory areas to improve safety and security.

51. RTOS Tick
• A periodic interrupt (typically from a timer)
that drives the RTOS timekeeping and
scheduling.

52. Hook Function
• User-defined functions called at specific points
in the RTOS kernel (e.g., task creation,
deletion).

53. Scheduler Locking
• Temporarily disables context switching to
prevent race conditions.

54. Nested Interrupts
• When an interrupt can itself be interrupted by
a higher-priority interrupt.

55. Reentrant Function
• A function that can be safely called by multiple
tasks or interrupts simultaneously.

56. Thread
• A lightweight process; often used
interchangeably with task in many RTOSes.

57. RTOS Porting
• Adapting the RTOS to run on a different
processor or hardware platform.

58. System Call
• A request made by a program to the RTOS
kernel for services (e.g., creating a task).

59. Bootloader
• A small program that initializes the hardware
and loads the RTOS or main firmware.

60. RTOS API
• A set of functions provided by the RTOS for
tasks, timing, communication, etc.