Declarations, definitions, init

Each definition is a declaration, but not each declaration is also a definition.

Declarations

• a declaration is a statement that introduces a name into a scope
• declare variables/functions before use
• declarations say how something can be used, not how it’s implemented
• in function declaration, named parameters are not necessary, but useful

Definitions

• a definition fully specifies the entity declared
• sets aside memory for the variable

Initialisation

ways of initialising:

• = syntax — double d = 2;
• () syntax — vector<int> v(10);
  • specifies number of elements
• {} syntax — vector<int> v{1,2,3};
  • gives a “vector literal“

with const, initialisation is mandatory