CHAPTER 4 Structures

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1 CHAPTER 4 Structures Page 1

2 Structures: Arrays are one of the most widely used data structures in programming languages. The limitation of arrays, however, is that all the elements must be of the same type. Structures overcome this problem by allowing the programmer to have an unlimited number of elements (members) of different data types. Structure Definition: Structures are user defined data types built using elements (members) of other data types. Typically there are two steps to implement structures in a program. 1. Create the structure declaration. Normally, structure is declared before the main() function. 2. Define variables of the structure to hold data. Structure variables are created inside the main() function. Structure Declaration General format of a structure declaration: struct structure-name Variable declaration; // more declaration may follow ; struct is a keyword followed by the structure-name(may be any name given by user). Note: A semicolon is required after the closing brace of the structure declaration. Page 2

3 Example: struct student long int ID; char name[100]; float mark[3]; float sum; float average; ; In the above declaration, structure members marks[3], sum and average are the same data types(float). Instead of declaring in three different lines, we can do the same in one line. float marks[3],sum,average; Many programmers prefer to place each member declaration on a separate line, however, for increased readability. Structure Variables: Structure variables are declared like variables of other data types. The general format is: structure-name variable1,variable2, ; Example: For the above structure student, variables can be created like student x,y; student std[10]; student *sptr; Here are some other examples of structure declarations and variable declarations. struct time int hour; int minutes; int seconds; ; Page 3

4 Structure variable can be declared like, time now; Another example is struct date int day; int month; int year; ; Structure variable can be declared like, date today; Accessing Members of Structure: Members of a structure(or a class) are accessed through the member access operators such as 1. The dot operator(.) 2. The arrow operator(->) Using dot (.) operator: Structure members are accessed through dot(.) operator, when the structure variables are normal variables. Example Program: #include<iostream> using namespace std; struct date int day; int month; int year; ; Page 4

5 int main() date today; today.year=2012; cout<<"enter the day"<<endl; cin>>today.day; cout<<"enter the month"<<endl; cin>>today.month; cout<<"today Date is:"<<today.day<<"-"<<today.month <<"-"<<today.year<<endl; return(0); Output: Enter the day 01 Enter the month 03 Today Date is: Using arrow (->) operator: Structure members are accessed through arrow(->) operator, when the structure variables are pointer variables. Example Program: #include<iostream> using namespace std; struct time int hour; int minutes; int seconds; ; Page 5

6 int main() time *t,now; t=&now; cout<<"enter the current hour"<<endl; cin>>now.hour; cout<<"enter the current minutes"<<endl; cin>>now.minutes; cout<<"enter the current seconds"<<endl; cin>>now.seconds; cout<<"the Current Time is"<<t->hour<<":"<<t->minutes<<":" <<t->seconds<<endl; return(0); Output: Enter the current hour 06 Enter the current minutes 10 Enter the current seconds 55 The Current Time is6:10:55 Array of Structures: Array is used to create the number of variables of same data type. So that, array can be used to create the number of structure variables. Example: Write a C++ program that reads the name, ID and average marks of 5 students using array of structures then print this list sorted alphabetically. The program must contain 3 functions for reading, printing and sorting. Page 6

7 Program: #include<iostream> #include<string> using namespace std; struct student char name[20]; long int id; float avg; ; void reading(student[],int); void sorting(student[],int); void printing(student[],int); void swap(student*,student*); int main() student st[5]; reading(st,5); sorting(st,5); printing(st,5); return(0); void reading(student s[],int size) int i; for(i=0;i<size;i++) cout<<"enter the Name of student"<<i<<endl; cin>>s[i].name; cout<<"enter the id of student"<<i<<endl; cin>>s[i].id; cout<<"enter the average marks of student"<<i<<endl; cin>>s[i].avg; Page 7

8 void printing(student s[],int size) int i; for(i=0;i<size;i++) cout<<s[i].name<<"\t\t"<<s[i].id<<"\t\t"<<s[i].avg<<endl; void sorting(student s[],int size ) int i,j; for(i=0;i<size;i++) for(j=0;j<size-1;j++) if(strcmp(s[j].name,s[j+1].name)>0 ) swap(&s[j],&s[j+1]); void swap(student *s1, student *s2) student temp; temp=*s1; *s1=*s2; *s2=temp; Output: Enter the Name of student0 salma Page 8

9 Enter the id of student Enter the average marks of student Enter the Name of student1 ayoob Enter the id of student Enter the average marks of student Enter the Name of student2 qasim Enter the id of student Enter the average marks of student Enter the Name of student3 othman Enter the id of student Enter the average marks of student Enter the Name of student4 maged Enter the id of student Enter the average marks of student ayoob maged othman qasim salma Page 9

10 Exercises: 1. Write a C++ program to read the name, number and salary of 5 employees using array of structures, and then perform the following according to the user choice. 1. Search the employee according to the number 2. Search the employee according to the name 3. Sort the list in ascending order according to the salary 4. Sort the list alphabetically 5. Exit 2. Write a C++ program to read the name, account number and balance amount in the account of 5 customers by using array of structures, and then perform the following according to the user choice. 1. Deposit the amount in their account 2. Withdrawal the amount from their account 3. Display the name, account number and balance of the customers. Page 11

Chapter 10 C Structures, Unions, Bit Manipulations

Chapter 10 C Structures, Unions, Bit Manipulations Skipped! Skipped! and Enumerations Skipped! Page 416 In programming languages, Arrays (Chapter 6) allows programmers to group elements of the same type