1. Embedded Systems Development Selecting a language for a real-time embedded system

2. Embedded Systems In order to select a language for real-time embedded system we need to ask two questions –What languages are available? –What do we want from these languages?

3. Embedded Systems There are four criteria that we can adopt for language selection –Essential features –Primary features –Secondary features –Perfomance

4. Embedded Systems Essential features –Assembley language MC interface –Absolute addressing –Access/control of H/W –Bit manipulation –Interrupt handling –Pointers –Specification for time delays –Processor extensions

5. Embedded Systems The primary features are: –Well defined language standard –Well defined behaviour –Strong data typing/ Rigorous control structures –Modular structure - seperate compilation –Exception handling –Tasking facilities –RTOS/RTEX interfaces –Maths library well defined

6. Embedded Systems The secondary features are: –Good syntax and layout –Multitasking - language and rt support –Interfaces to other HLLs –Safety critical subset/features –Comprehensive libraries –Object Orientated programming constructs

7. Embedded Systems The performance features are: –Setting task deadlines –Evaluation of code execution times –Deterministic code –Selection of scheduling strategies –Timing analysis mechanism

8. Embedded Systems Ada Modularity separate compilation tasking exception handling reliable readable portable large language complex weak tasking model no safety critical no OOP (Ada95)

9. Embedded Systems C highly efficient easy to learn powerful widely available lots of tools/GUIs difficult to read portability problems no OOP interface undefined behaviour weak type checking

10. Embedded Systems C++ builds on C Object orientated good type checking portable HLL interfaces difficult to read memory leakage library incompatibility

11. Embedded Systems Modula2 Modular construction Systems programming Concurrency interrupt handling portable not widely used few compilers no OOP

12. Embedded Systems Oberon/Oberon2 Modular Concurrency interrupt handling Systems programming OOP Support not widely used no standard limited OOP model

13. Embedded Systems Assembly language and MC interface –Ada - standard library package or pragma –C - embedded with asm or function call –C++ - similar to C –Modula2 - no defined standard facilties –Oberon-2 - highly systems dependant

14. Embedded Systems Absolute addressing –Ada - type ADDRESS in SYSTEM package –C - uses pointers –C++ - as with C or library interfaces –Modula2 - SYSTEM library –Oberon-2 - as with Modula2

15. Embedded Systems Well defined language standard? –Ada - Yes –C - Yes but compiler differences exist –C++ - still evolving –Modula2 - Yes but few around –Oberon-2 - informal standard

16. Embedded Systems Well defined behaviour? –Ada - yes few differences –C - No large discrepancies –C++ - No better than C –Modula2 - yes rigorous –Oberon-2 - evolving but strict

17. Embedded Systems Strong type checking? –Ada - yes very strong –C - very weak use of pointers –C++ - better than C but pointer problems –Modula2 - strongly typed –Oberon-2 - strongly type OOP features?

18. Embedded Systems Rigorous control structures? –Ada - yes but has goto –C - care needed with switch, for and jumps –C++ - similar to C –Modula2 - yes but has EXIT/RETURN –Oberon-2 similar to Modula2

19. Embedded Systems Modular structure/ seperate compilation? –Ada - Yes built into language –C - Yes, pointer problems –C++ - no explicitly modular - can have class –Modula2 - Yes, implemantation & definition –Oberon-2 - similar to Modula2, implementation

20. Embedded Systems Exception handling –Ada - standard for language & user defined –C - no standard use jumps –C++ - version 3.0 support it –Modula2 - no standard - some support –Oberon-2 - no standard

21. Embedded Systems Tasking? –Ada - yes built in –C - no can be implemented with pointers –C++ no can be implemented –Modula2 - yes using PROC –Oberon-2 - can be implemented

22. Embedded Systems Syntax and layout –Ada - Good highly readable –C - well specificed syntax but bad overall –C++ - even worse than C –Modula2 - highly readable EBNF/VDM –Oberon-2 - very readable EBNF

23. Embedded Systems Multitasking rt support –Ada - integral part of language –C - not supported –C++ - not supported libraries? –Modula2 - implemented using coroutines –Oberon-2 - optional library feature