Basic concepts of programming languages

Basic concepts of programming languages

1. Policy

   • Static
     • Compiler decides an issue
     • At compile time
   • Dynamic
     • Decide when execute program
     • At run time

2. Scope

   • Static or lexical
     • Determine scope of declaration just looking at code
   • Dynamic
     • As program runs, declaration of x could refer to any of several different declarations

3. Environment and States

4. Block

   • Grouping of declarations and statements
   • Block structure
     • Allows blocks to be nested inside eachother

5. Explicit Access Control

   • Use of keywords to support encapsulation by restrincting access
     • public, private, protected

6. Parameters

   • Parameters types
     • Actual
       • Used in the call of the procedure
     • Formal
       • Used in the procedure definition
   • Passing Mechanisms
     • Called-by-Value
       • The actual parameter is evaluated or copied
     • Called-by-Reference
       • Address of actual parameter is passed to the callee as the value of formal parameter
       • Changes to formal parameter thus appear as changes to actual parameter
       • Aliasing
         • Two formal parameter can refer to the same location
     • Called-by-Name
       • The callee executes as if actual parameter were substituted literally for formal parameter

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