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LBC, Session 11 Advanced Data types FPT APTECH COMPUTER EDUCATION HANOI Objectives • • • • • • • • • • • Explain structures and their use Define structures Declare structure variables Explain how structure elements are accessed Explain how structures are initialized Explain how assignment statements are used with structures Explain how structures can be passed as arguments to functions Use arrays of structures Explain the initialization of structure arrays Explain how structure pointers can be passed as arguments to functions Explain the typedef keyword LBC/Session 11 2 Structures • A structure consists of a number of data items, which need not be of the same data type, grouped together • The structure could hold as many of these items as desired 1 I I L L U S I O N B A C H 1 Variable L L U Name of the book Author Edition S I O N Array LBC/Session 11 3 Defining a Structure • Forms a template for creating structure variables • The variables in the structure are called structure elements or structure members • Example: struct cat { char bk_name [25]; char author [20]; int edn; float price; }; LBC/Session 11 4 Declaring Structure Variables • Once the structure has been defined, one or more variables of that type can be declared • Two ways of declaring struct variables. Right after the close bracket of struct declaration. Separated from the struct declaration. LBC/Session 11 5 Declaring Structure Variables (cont.) struct cat { char bk_name[25]; char author[20]; int edn; float price; } books1, books2; struct cat { char bk_name[25]; char author[20]; int edn; float price; }; struct cat books1, books2; Or: struct cat books1; struct cat books2; LBC/Session 11 6 Accessing Structure Elements Structure elements are referenced through the use of the dot operator (.), also known as the membership operator Syntax: structure_name.element_name Example: scanf(“%s”, books1.bk_name); LBC/Session 11 7 Initializing Structures • Can be initialized at the time of declaration struct employee { int no; char name [20]; }; • Variables emp1 and emp2 of the type employee can be declared and initialized as: struct employee emp1 = {346, “Abraham”}; struct employee emp2 = {347, “John”}; LBC/Session 11 8 Assignment Statements Used with Structures-1 • Possible to assign the values of one structure variable to another variable of the same type using a simple assignment statement • If var1 and var2 are structure variables of the same type, the following statement is valid var2= var1; LBC/Session 11 9 Assignment Statements Used with structures - 2 • In cases where direct assignment is not possible, the built-in function memcpy() can be used • Syntax: memcpy (char * destn, char &source, int nbytes); • Example: memcpy (&books2, &books1, sizeof(struct cat)); LBC/Session 11 10 Structures within Structures Possible to have one structure within another structure. A structure cannot be nested within itself struct issue { char borrower [20]; char dt_of_issue[8]; struct cat books; }issl; The way to access the elements of this structure is similar to the one applied for normal structures, issl.borrower To access elements of the structure cat, a part of structure issue, issl.books.author LBC/Session 11 11 Passing Structures as Arguments • Parameters of a function can be structures. • This facility is used to pass groups of logically related data items together instead of passing them one by one • The type of the argument should match the type of the parameter LBC/Session 11 12 Array of Structures • A common use of structures is in arrays of structures • A structure is first defined, and then an array variable of that type is declared • Example: struct cat books[50]; • To the access the variable named author of the fourth element of the array books: books[4].author LBC/Session 11 13 Initialization of Structure Arrays • Structure arrays are initialized by enclosing the list of values of its elements within a pair of braces • Example: struct unit { char ch; int i; }; struct unit { {'a', {'b', {'c', }; series[3] = 100} 200} 300} LBC/Session 11 14 Example of structure arrays struct strucintcal { char name[20]; int numb; float amt; }; void intcal(struct strucintcal); void main() { struct strucintcal customers[50]; int i; LBC/Session 11 15 Example of structure arrays (cont.) /* Accepts data into the structure */ for (i=0; i operator is used to access the elements of a structure using a pointer • Example: struct cat *ptr_bk; ptr_bk = &books; printf(“%s”, ptr_bk->author); • Structure pointers passed as arguments to functions enable the functions to modify the structure elements directly LBC/Session 11 18 Example of Pointers to Structures struct strucintcal { char name[20]; int numb; float amt; }; void intcal(struct strucintcal); void main() { struct strucintcal *ptr_customers; int i, n; LBC/Session 11 19 Example of Pointers to Structures (cont.) printf("\nEnter the number of customers: "); scanf(“%d”,&n); ptr_customers=(struct structintcal *) malloc(n *sizeof(struct strucintcal)); clrscr(); /* Accepts data into the structure */ for (i=0; iname); LBC/Session 11 20 Example of Pointers to Structures (cont.) printf("\nEnter Customer number: "); scanf("%d", ptr_customers+i)->numb); printf("\nEnter Principal amount: "); scanf("%f", ptr_customers+i)-> amt); intcal(*(ptr_customers+i)); } getch(); } void intcal(struct strucintcal){} LBC/Session 11 //see slide 16 21 The typedef keyword • A new data type name can be defined by using the keyword typedef • Does not create a new data type, but defines a new name for an existing type • Syntax: typedef type name; • typedef cannot be used with storage classes LBC/Session 11 22 Example of typedef typedef float deci; typedef deci point; void main() { float num1; deci num2; point sum; printf("\nEnter the values of num1 and num2: "); scanf(“%f%f”,&num1, &num2); sum= num1 + num2; printf("\n The summary of num1 and num2 is: %f“, sum); getch(); } LBC/Session 11 23 [...]... strucintcal customers[50]; int i; LBC /Session 11 15 Example of structure arrays (cont.) /* Accepts data into the structure */ for (i=0; inumb); printf("\nEnter Principal amount: "); scanf("%f", ptr_customers+i)->... Possible to have one structure within another structure A structure cannot be nested within itself struct issue { char borrower [20]; char dt_of_issue[8]; struct cat books; }issl; The way to access the elements of this structure is similar to the one applied for normal structures, issl.borrower To access elements of the structure cat, a part of structure issue, issl.books.author LBC /Session 11 11 Passing... rate * yrs) / 100; printf ("\nThe customer name is %s", abc.name); printf("\nThe customer number is %d", abc.numb); printf("\nThe amount is %f", abc.amt); printf("\nThe interest is %f", si); return; } LBC /Session 11 17 Pointers to Structures • Structure pointers are declared by placing an asterisk(*) in front of the structure variable’s name • The -> operator is used to access the elements of a structure... ptr_customers+i)-> amt); intcal(*(ptr_customers+i)); } getch(); } void intcal(struct strucintcal){} LBC /Session 11 //see slide 16 21 The typedef keyword • A new data type name can be defined by using the keyword typedef • Does not create a new data type, but defines a new name for an existing type • Syntax: typedef type name; • typedef cannot be used with storage classes LBC /Session 11 22 Example of typedef typedef... facility is used to pass groups of logically related data items together instead of passing them one by one • The type of the argument should match the type of the parameter LBC /Session 11 12 Array of Structures • A common use of structures is in arrays of structures • A structure is first defined, and then an array variable of that type is declared • Example: struct cat books[50]; • To the access the... author of the fourth element of the array books: books[4].author LBC /Session 11 13 Initialization of Structure Arrays • Structure arrays are initialized by enclosing the list of values of its elements within a pair of braces • Example: struct unit { char ch; int i; }; struct unit { {'a', {'b', {'c', }; series[3] = 100} 200} 300} LBC /Session 11 14 Example of structure arrays struct strucintcal { char name[20];... float num1; deci num2; point sum; printf("\nEnter the values of num1 and num2: "); scanf(“%f%f”,&num1, &num2); sum= num1 + num2; printf("\n The summary of num1 and num2 is: %f“, sum); getch(); } LBC /Session 11 23 ... into the structure */ for (i=0; iname); LBC /Session 11 20 Example of Pointers to Structures (cont.) printf(" Enter Customer... struct strucintcal *ptr_customers; int i, n; LBC /Session 11 19 Example of Pointers to Structures (cont.) printf(" Enter the number of customers: "); scanf(“%d”,&n); ptr_customers=(struct structintcal... LBC /Session 11 15 Example of structure arrays (cont.) /* Accepts data into the structure */ for (i=0; i