PD1: Chapter 3: Concerning Variables

• What is the definition of a variable in C# according to the C# language reference?

  A variable is defined in the C# language reference: C#6.0 draft specification.
• What are the two types of variables in C#?

  • Instance variable: declared outside any method, belongs to the instance of the class.
  • Local variable: defined inside a code block (like a method).
• Why is it important to distinguish between instance and local variables?

  Because a variable is either an instance variable or a local variable, never both, never neither.
• What is the scope of an instance variable in C#?

  The scope of an instance variable is the complete class.
• How does the scope of a local variable differ from that of an instance variable?

  A local variable is known only within its defining method, while an instance variable is known throughout the entire class.
• What is the significance of the textual position of a local variable's definition?

  A local variable can only be used after its definition, making the textual position important.
• What happens when a local variable has the same name as an instance variable?

  The local variable shadows the instance variable within the common scope.
• How does the compiler distinguish between a local variable and an instance variable with the same name?

  The compiler refers to the closest encapsulating definition, which is the local variable.

  
• What must be done to refer to an instance variable when a local variable with the same name exists?

  You must prefix the instance variable name with "this." to refer to it.
• What is the lifetime of a local variable in a method?

  The lifetime of a local variable is from the execution start to the execution end of that method.
• How does the default value assignment differ between local and instance variables?

  A local variable does not get a default value unless explicitly assigned, while an instance variable gets a default value when defined without an explicit value.
• What is the default value for numerical datatypes in C#?

  The default value for numerical datatypes is 0.
• What is the default value for the boolean datatype in C#?

  The default value for the boolean datatype is False.
• What are the guidelines for naming instance and local variables in C#?

  • Instance variable names must start with an underscore.
  • Local variable names are not allowed to start with an underscore.
• What is the rule of thumb for choosing between instance and local variables?

  Use a local variable when possible, and an instance variable only when a local variable is not sufficient.
• What are the implications of using instance variables in terms of code complexity?

  • Unnecessary instance variables introduce extra complexity.
  • Each code update must consider all instance variables.
  • More instance variables increase potential errors.
• What does it mean that C# is a static typed language?

  It means each variable definition contains the datatype of that variable.
• What are compile time errors in a statically typed language like C#?

  Errors detected during compilation due to type mismatches.
• What is the definition of variable initialization?

  Initialization is the assignment of the first value to a variable.
• What is the difference between initialization and assignment?

  Initialization is the first assignment to a variable, while assignment can occur multiple times.
• What are the key takeaways from Chapter 3 regarding variables?

  • Instance and local variables are not the same.
  • A variable has an associated scope, different from its lifetime.
  • Some variables have a default value.
  • Choosing between instance and local variables influences code quality.