Concurrency is naturally divided into: 

1) Instruction level concurrency, 

2) Statement level concurrency (executing two or more statements simultaneously), 

3) Program unit level concurrency(execute two or more subprogram units simultaneously) and 

4) Program level concurrency (executing two or more programs simultaneously). 


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  2. Louden, “Programming Languages: Principles & Practices” , Cengage Learning
  3. Tucker, “Programming Languages: Principles and paradigms “, Tata McGraw –Hill.
  4. E Horowitz, “Programming Languages”, 2nd Edition, Addison Wesley