Chapter 6 Structures

1. Chapter 6Structures Ku-Yaw Chang canseco@mail.dyu.edu.tw Assistant Professor, Department of Computer Science and Information Engineering Da-Yeh University

2. Structures • A structure • A collection of one or more variables, possibly of different types, grouped together under a single name for convenient handling. • Also called records in some language, notably Pascal • Examples • An employee is described by a set of attributes • Name • Address • Social security number • Salary • A point is a pair of coordinates • A rectangle is a pair of points Structures

3. 6.1 Basics of Structures • A point • x coordinate (integer) • y coordinate (integer) • The above two components can be placed in a structure declared like this: struct point { int x; int y;}; • A structure tag • an optional name: point • Members • x and y Structures

4. More examples struct card { char * face; char * suit;}; struct employee { char firstName[20]; char lastName[20]; int age; char gender; double hourlySalary;struct employee person; /* error*/ struct employee * ePter; /* pointer */}; 6.1 Basics of Structures Structures

5. 6.1 Basics of Structures • A structure declaration • Reserve no storage (memory) • Structure variables are defined like variables of other types • struct point pt; • struct card aCard, deck[52], * cardPtr; • struct card { char * face; char * suit;} aCard, deck[52], * cardPtr; Structures

6. 6.1 Basics of Structures • A member of a particular structure is referred to in an expression by a construction of the form – dot operatorstructure-name . member • For example, • To print the coordinates of the point pt • printf(“%d, %d”, pt.x, pt.y); • To compute the distance from the origin (0,0) to pt • double dist, sqrt(double);dist = sqrt( (double)pt.x * pt.x + (double)pt.y * pt.y) Structures

7. 6.1 Basics of Structures • A member of a particular structure can also be referred by arrow operator • For example, • struct card aCard, * cardPtr;cardPtr = &aCard;printf(“%s”, cardPrt->suit); Structures

8. 6.1 Basics of Structures • Structures can be nested • struct rect { struct point pt1; struct point pt2;}; • For example, • struct rect screen;screen.pt1.x Structures

9. 6.7 typedef • typedef • Create new data type names • typedef int Length; • Make the name Length a synonym for int • Length len, maxlen; • typedef char * String; • Make String a synonym for char * or character pointer • String p; • Typedef struct tnode * Treeptr; Structures

10. 6.8 Unions • A union • A variable that may hold (at different times) objects of different types and sizes • Provide a way to manipulate different kinds of data in a single area of storage • Example • union u_tag {intival; float fval; char * sval;} u; • The variable u will be large enough to hold the largest of three types. Structures

11. To be continued…