Structures Chapter 4

Structures Variables of simple data types such as float , char, and int represent one item of information A structure is collection of simple variables. Variables can be of different types Data items in structure called members of the structure A structure is collection of data while a class is collection of both data and functions Members of structure are public by default while in class members are private by default

Syntax of Structure Syntax Example Struct structure-name { member_type1 member_name1; member_type2 member_name2; member_type3 member_name3; . . } struct-variable; Struct part { int modelnumber; int partnumber; float cost; } part1;

Example ////////////////////////////////////// struct part { int modelnumber; int partnumber; float cost; }; int main() part part1; part1.modelnumber = 6244; part1.partnumber = 373; part1.cost = 217.55; cout<<“Model: ”<< part1.modelnumber; cout<<“, Part: ”<< part1.partnumber; cout<<“, cost $: ”<< part1.cost; return 0; }

structures The structure definition is only blue print for creation of variables Defining a structure variable reserves space in memory part part1; part part2; is similar when we are defining a variable e.g. int var1 Members of structures are accessed by its variable following dot operator (member access operator) part1.modelnumber = 6244

Cont’d Another way to initialize structure members are part part1 = {6244,373,217.55}; One structure variable can be assigned to another part2 = part1; The value of each member of part1 is assigned to corresponding member of part2 One structure variable can assigned to another only when they are of the same structure type

Structure within structures Structures can be nested within other structures Example struct Distance { int feet; float inches; }; ////////////////////////////////// struct Room Distance length; Distance Width; } int main() { Room dining; dinning.length.feet = 13; dinning.length.inches =6.5; dinning.width.feet = 10; dinning.width.inches =0.0; Float l = dinning.length.feet + dinning.length.inches/12; Float w= dinning.width.feet + dinning.width.inches/12; Cout<<“Dining room area is ”<< l*w; return 0; }

Enumeration Another way to define own data type is enumeration Enumerated types work when you know in advance a finite list of values that a data type can take on e.g. enum days_of_weeks { Sun, Mon, Tue, Wed, Thu, Fri, Sat}; An enum defines a set of all names that will be permissible values of type. These permissible values are called enumeration Also enumeration is list of values and each value has its specific name

Cont’d Variable can be defined like in structure days_of_week day1, day2; These variables can be given any of the values listed in the enum declaration. E.g. day1 = Mon; , day2 = Thu; day1 = halloween; // illegal Enumerations are treated internally as integers First name in list is given value 0, next name is 1 and so on.

Example enum days_of_week{Sun, Mon, Tue, Wed, Thu, Fri, Sat}; int main() { days_of_week day1, day2; day1 = Mon; day2 = Thu; int diff = day2 – day1; // can do integer arithmetic cout<<“days between = ”;<<diff<<endl; if(day1<day2) cout<<“day1 comes before day2 ”; return 0; }