User Defined data Types

Transcription

1 User Defined data Types

2 typedef datatype user_defined_data_type typedef int salary; salary emp1,emp2; salary x; typedef char sentence[50]; sentence header,footer; char header[50],footer[50]; 5/1/2006 Computer Programming TA 103 BE I year 2

3 enumerated data types An enumerated data type stores specific values enum productpen,pencil,eraser,paper}; members of an enumerated data types are constants. e.g. pen,pencil are constants. members are unique and cannot be duplicate. enum product p1; p1=pen; members of an input variable cannot be used with an input function like scanf; Members are assigned integer values by the compiler. By default the first member gets the value 0, second get 1 and so on. 5/1/2006 Computer Programming TA 103 BE I year 3

4 overriding default values enum productpen=1,pencil,eraser,paper} 5/1/2006 Computer Programming TA 103 BE I year 4

5 There is no data type in C that allows you to store different types in one unit.however, you can store all this information as one unit in a structure and use the structure to write records in a file. 5/1/2006 Computer Programming TA 103 BE I year 5

6 The variables contained in a structure are called its members. The data types of these members can be different. Structures can contain arrays and pointers. 5/1/2006 Computer Programming TA 103 BE I year 6

7 Member names with in a structure are unique. However, different structures can have the members with the same name. There is no limit on number of members a structure can contain. 5/1/2006 Computer Programming TA 103 BE I year 7

8 #include<stdio.h> struct date int day; char month[15]; int year; }; main () } 5/1/2006 Computer Programming TA 103 BE I year 8

9 The declaration of a structure does not reserve any bytes in memory for the structure. The declaration only indicates the variables that can be stored in a structure. 5/1/2006 Computer Programming TA 103 BE I year 9

10 #include<stdio.h> struct date int day; char month[15]; int year; }; main () struct date dat1,dat2; } 5/1/2006 Computer Programming TA 103 BE I year 10

11 #include<stdio.h> struct date int day; char month[15]; int year; } dat1,dat2; main () } 5/1/2006 Computer Programming TA 103 BE I year 11

12 #include<stdio.h> struct int day; char month[15]; int year; } dat1,dat2; main () } 5/1/2006 Computer Programming TA 103 BE I year 12

13 #include<stdio.h> typedef struct int day; char month[15]; int year; } date; main () date day1,day2; } 5/1/2006 Computer Programming TA 103 BE I year 13

14 structure variables can be accessed by using dot operator. e.g. dat1.day=6; or printf( %d, dat2.year); 5/1/2006 Computer Programming TA 103 BE I year 14

15 When a structure is passed as an argument to a function, structure is defined before a function. Entire structure or a member of a structure can b passed to a function as an argument. 5/1/2006 Computer Programming TA 103 BE I year 15

16 #include<stdio.h> struct date int month; int day; int year; }; void PrintDate(struct date) ; main () struct date today = 4,18,2006}; PrintDate(today); } void PrintDate(struct date dt) printf( Month = %d, dt.month); printf( Day = %d, dt.day); printf( Year = %d, dt.year); } 5/1/2006 Computer Programming TA 103 BE I year 16

17 #include<stdio.h> struct BankAccount int ActNo; char *name; int balance; }; struct BankAccount adjust(struct BankAccount); main() struct BankAccount customer = 333, sham, 3000}; printf( %d %s %d \n, customer.actno, customer.name, customer.balance); customer=adjust(customer); printf( %d %s %d \n, customer.actno, customer.name, customer.balance); } struct BankAccount adjust(struct BankAccount cust) cust.actno=645; cust.name= ram ; cust.balance=4000; return cust; } 5/1/2006 Computer Programming TA 103 BE I year 17

18 5/1/2006 Computer Programming TA 103 BE I year 18