Control Structures

​Express Semantics

• Semantics

  • Meaning... What you are doing

  • Important in Computer Science

• Syntax

  • Grammar... How do you express invalid "sentences".

  • Varies by language, frequently changes

• Valid syntax dose not imply correct Semantics.

  • Cows Ievitate regularly

    • Valid syntax

    • Doesn't make sense (students do this a lot in C++)

Conflicting Ideals

• Type safety

• Run-time performance

• Portability across platforms

• Compatibility with other code

• Ease of construction

• Ease of maintenance

Programming Goals

• Abstraction

• Correctness

• Efficiency

• Robustness

• Readability

• Reuse

• Modularity

Control Structures

Sequence

• The ordering of statements

• Can include function calls

• Essentially no "Decisions" are made

Sequence

Selection

• Also called "branching"

• Allows a block of code to be executed or not based on a "Decision/Question"

• Allows for different paths through the code

Selection

Iteration

• Also called "iteration" and "looping"

• Allows a block of code to be executed repeatedly until a condition is satisfied

Iteration