Name: Reg. #:201 -EE- Date: Structures

Transcription

1 Name: Reg. #:201 -EE- Date: A structure is a collection of one or more variables, possibly of different types, grouped together under a single name for convenient handling. Structures are collections of related variables under one name. Structures may contain variables of many different data types in contrast to arrays that contain only elements of the same data type. Pointers and structures facilitate the formation of more complex data structures such as linked lists, queues, stacks and trees. Structure Definition Structures are derived data types as they are constructed using objects of other types. Consider the following structure definition: struct person char gender; int age; struct person *ptr; ; Keyword struct introduces the structure definition. The identifier person is the structure tag, which names the structure and is used with the keyword struct to declare variables of structure type. In this example, the structure type is struct person. Variables declared within the braces of the structure definition are the structure s members. Members of the same structure type must have unique names, but two different structure types may contain members of the same name without conflict. Each structure definition must end with a semicolon. The definition of structure person contains three members of type char and int and pointer to struct person. Structure members can be variables of primitive data types (e.g., int, float, etc.), or aggregates, such as arrays and other structures. A structure containing a member that is a pointer to the same structure type is referred to as self referential structure. Self referential structures are used to build linked data structures. Structure definitions do not reserve any space in memory; rather each definition creates a new data type that is used to define variables. Structure variables are defined like variables of other types. The definition struct person p1, p[50], *pptr; Structures declares p1 to be a variable of type struct person, declares p to be an array with 50 elements of type struct person and declares pptr to be a pointer to struct person. The only valid operations that may be performed on structures are the following: Assigning structure variables to structure variables of the same type, taking the address (&) of a structure variable, accessing the members of a structure variable and using the sizeof operator to determine the size of the structure variable. 1/6

2 Initializing Structures Structures can be initialized using initializer lists as with arrays. To initialize a structure follow the variable name in the definition with an equal sign and a brace-enclosed, comma-separated list of initializers. For example the declaration struct person p2 = F, 22; creates variable p2 to be of type struct person and initializes members gender to F and age to 22. If there are fewer initializers in the list than members in the structure, the remaining members are automatically initialized to 0 (or NULL if the member is a pointer). Structure variables defined outside a function definition (i.e., externally) are initialized to zero or NULL if they are not explicitly initialized in the external definition. Structure variables may also be initialized in assignment statements by assigning a structure variable of the same type, or by assigning values to the individual members of the structure. Accessing Members of Structures Two operators are used to access members of structures: The structure member operator (.) also called dot operator and the structure pointer operator (->) also called the arrow operator. The structure member operator accesses a structure member via the structure variable name. For example to print member age of structure variable p2, use the statement printf( %d, p2.age); // display age of p2 The structure pointer operator consisting of a minus (-) sign and greater than (>) sign with no intervening spaces accesses a structure member via a pointer to the structure. Assume that the pointer pptr has been declared to point to struct card and that the address of structure p2 has been assigned to pptr. To print member age of structure p2 with pointer pptr, use the statement printf( %d, p2 -> age); // display age of p2 Following program shows how to use an array of structures. char name; float price; int pages; ; b[5]; int a; 2/6

3 for(a=0;a<=4;a++) printf("enter name, price and pages\n"); scanf("%c%f%d",&b[a].name,&b[a].price,&b[a].pages); for(a=0;a<=4;a++) printf("%c%f%d\n",b[a].name,b[a].price,b[a].pages); The values of a structure variable can be assigned to another structure variable of the same type using the assignment operator. This is shown in the following program. struct employee char name[10]; int age; int salary; ; struct employee e1 = "Anita", 22, 56800,e2; e2=e1; printf("%s\t%d\t%d\n",e1.name,e1.age,e1.salary); printf("%s\t%d\t%d\n",e2.name,e2.age,e2.salary); Following program illustrates how to pass individual structure elements to a function. void display (char a1[],char a2[],int number); char name[50]; char author[25]; int code; ; 3/6

4 b1 = "Data Structures & Algorithm Analysis in C","Mark Allen Weiss",230; b2 = "Data Structures through C","YPK",230; b3 = "Data Structures using C & C++","Yedidyah Langsam",230; display(b1.name,b1.author,b1.code); display(b2.name,b2.author,b2.code); display(b3.name,b3.author,b3.code); void display (char a1[],char a2[],int number) printf("\n%-40s\t%-20s\t%d\n\n",a1,a2,number); A better way will be to pass the entire structure variable at a time. This method is shown in the following program. char name[50]; char author[25]; int edition; ; void display ( b); b1 = "Data Structures & Algorithm Analysis in C","Mark Allen Weiss",2; display(b1); void display ( b) printf("\n%-40s\t%-20s\t%d\n\n",b.name,b.author,b.edition); Following program illustrates the method to pass the address of a structure variable. char name[50]; char author[25]; int edition; ; 4/6

5 void display ( *b); b1 = "Data Structures & Algorithm Analysis in C","Mark Allen Weiss",2; display(&b1); void display ( *b) printf("\n%-40s\t%-20s\t%d\n\n",b->name,b->author,b->edition); LAB ASSIGNMENT 1) Create a structure to specify data on students given below: Roll number, Name, Department, Course, Year of joining Assume that there are not more than 450 students in the collage. (a) Write a function to print names of all students who joined in a particular year. (b) Write a function to print the data of a student whose roll number is given. 2) Create a structure to specify data of customers in a bank. The data to be stored is: Account number, Name, Balance in account. Assume maximum of 200 customers in the bank. a) Write a function to print the Account number and name of each customer with balance below Rs b) If a customer request for withdrawal or deposit, it is given in the form: Acct. no, amount, code (1 for deposit, 0 for withdrawal) Write a program to give a message, The balance is insufficient for the specified withdrawal. 3) An automobile company has serial number for engine parts starting from AA0 to FF9. The other characteristics of parts to be specified in a structure are: Year of manufacture, material and quantity manufactured. (a) Specify a structure to store information corresponding to a part. (b) Write a program to retrieve information on parts with serial numbers between BB1 and CC6. 4) A record contains name of cricketer, his age, number of test matches that he has played and the average runs that he has scored in each test match. Create an array of structure to hold records of 20 such cricketers and then write a program to read these records and arrange them in ascending order by average runs. 5/6

6 5) There is a structure called employee that holds information like employee code, name, date of joining. Write a program to create an array of the structure and enter some data into it. Then ask the user to enter current date. Display the names of those employees whose tenure is 3 or more than 3 years according to the given current date. 6) Write a menu driven program that depicts the working of a library. The menu options should be: 1. Add book information 2. Display book information 3. List all books of given author 4. List the title of specified book 5. List the count of books in the library 6. List the books in the order of accession number 7. Exit Create a structure called library to hold accession number, title of the book, author name, price of the book, and flag indicating whether book is issued or not. 7) Write a program that compares two given dates. To store date use structure say date that contains three members namely date, month and year. If the dates are equal then display message as "Equal" otherwise "Unequal". 6/6