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typedef in C is used to create alternative names to the existing data types. It will be used when naming of the predefined data types becomes slightly complicated to use in the programs.
typedef is basically a reserved keyword that we use in order to create an alias name for a specific data type.
Syntax
typedef data_type new_your_data_type;Example
typedef float my_float;
my_float b= 5.0;Example Code
#include<stdio.h>
int main()
{
typedef int myint;
myint a = 5; // int a = 5;
printf("a=%d",a);
return 0;
}Output
a=5Creating typedef for structures
Method 1
Syntax
typedef struct tagname
{
statement(S);
} alias_name;Example
typedef struct student
{
int rollno;
char name[10];
} stud;
stud s1, st[20];Method 2
Syntax
struct tagname
{
statement(S);
};
typedef struct tagname alias_name var_list;Example Code
struct phonebook
{
NAME pname; // pname is a variable of type name
char mob_no[11];
};
typedef struct phonebook phentry;Example: Using typedef for structures
#include<stdio.h>
typedef struct name
{
char first_name[20];
char last_name[20];
}NAME; // NAME is a new datatype for struct name
struct phonebook
{
NAME pname; // pname is a variable of type name
char mob_no[11];
};
typedef struct phonebook phentry; // phentry is a new datatype for struct phonebook
int main()
{
phentry p1,p2; // p1 and p2 are variables for phentry
printf("Enter the details of the first person:\n");
printf("Enter the first name of the person \t");
gets(p1.pname.first_name);
printf("Enter the last name of the person \t");
gets(p1.pname.last_name);
printf("Enter the mobile number of the person \t");
gets(p1.mob_no);
printf("Enter the details of the second person:\n");
printf("Enter the first name of the person \t");
gets(p2.pname.first_name);
printf("Enter the last name of the person \t");
gets(p2.pname.last_name);
printf("Enter the mobile number of the person \t");
gets(p2.mob_no);
printf("****Details are****\n");
printf("---------------------\n");
printf("%s\t %s\t %10s\n",p1.pname.first_name,p1.pname.last_name,p1.mob_no);
printf("%s\t%s\t%10s\n",p2.pname.first_name,p2.pname.last_name,p2.mob_no);
}Output
C:\TDM-GCC-64>gcc 4_typedef1.c -o 4t1
C:\TDM-GCC-64>4t1
Enter the details of the first person:
Enter the first name of the person abi
Enter the last name of the person kumar
Enter the mobile number of the person 123456
Enter the details of the second person:
Enter the first name of the person ram
Enter the last name of the person laxman
Enter the mobile number of the person 23456
****Details are****
---------------------
abi kumar 123456
ram laxman 23456Views: 0