Declarations, definitions, init.md (805B)
1 +++ 2 title = 'Declarations, definitions, init' 3 +++ 4 # Declarations, definitions, init 5 Each definition is a declaration, but not each declaration is also a definition. 6 7 ## Declarations 8 - a declaration is a statement that introduces a name into a scope 9 - declare variables/functions before use 10 - declarations say how something can be used, not how it’s implemented 11 - in function declaration, named parameters are not necessary, but useful 12 13 ## Definitions 14 - a definition fully specifies the entity declared 15 - sets aside memory for the variable 16 17 ## Initialisation 18 ways of initialising: 19 20 - = syntax — `double d = 2;` 21 - () syntax — `vector<int> v(10);` 22 - specifies number of elements 23 - {} syntax — `vector<int> v{1,2,3};` 24 - gives a “vector literal" 25 26 with const, initialisation is mandatory