Skip to main content

Enumerated Data Type


Enumeration (or enum) is a user defined data type in C. It is mainly used to assign names to integral constants, the names make a program easy to read and maintain.The symbolically declared members are integer constants. The keyword enum is used to declare an enumeration type. The general construct used to declare an enumeration type is
enum tag_name {member1, member2, member3,..,member} variable1, variable2,..,variable n
In this declaration, either tag_name or variable may be omitted or both may be present. But at least one of them must exist in this declaration construct.
The members are integer constants. By default the first member member1 assigned value 0 member2 assigned value 1 and so on.
Eg:
enum week{Mon, Tue, Wed,Thu,Fri,Sat};
enum week day;
// Or
enum week{Mon, Tue, Wed,Thu,Fri,Sat}day;

#include <stdio.h>
enum day {sunday, monday, tuesday, wednesday, thursday, friday, saturday};
int main()
{
enum day d = thursday;
printf("The day number stored in d is %d", d);
return 0;
}
We can explicitly assign values also.Two enum names can have same value. For example, in the following C program both ‘Failed’ and ‘Freezed’ have same value 0.
#include <stdio.h>
enum State {Working = 1, Failed = 0, Freezed = 0};
 int main()
{
   printf("%d, %d, %d", Working, Failed, Freezed);
   return 0;
}
Output:
1, 0, 0
If we do not explicitly assign values to enum names, the compiler by default assigns values starting from 0. For example, in the following C program, sunday gets value 0, monday gets 1, and so on.
#include <stdio.h>
enum day {sunday, monday, tuesday, wednesday, thursday, friday, saturday};
 int main()
{
    enum day d = thursday;
    printf("The day number stored in d is %d", d);
    return 0;
}
Output:
The day number stored in d is 4

We can assign values to some name in any order. All unassigned names get value as value of previous name plus one.
#include <stdio.h>
enum day {sunday = 1, monday, tuesday = 5, wednesday, thursday = 10, friday, saturday};
 int main()
{
    printf("%d %d %d %d %d %d %d", sunday, monday, tuesday,
            wednesday, thursday, friday, saturday);
    return 0;
}
Output:
1 2 5 6 10 11 12
The value assigned to enum names must be some integeral constant, i.e., the value must be in range from minimum possible integer value to maximum possible integer value.
All enum constants must be unique in their scope. For example, the following declaration fails in compilation.
enum state  {working, failed};
enum result {failed, passed};

Enum vs Macro
We can also use macros to define names constants. For example we can define ‘Working’ and ‘Failed’ using following macro.
#define Working 0
#define Failed 1
#define Freezed 2
There are multiple advantages of using enum over macro when many related named constants have integral values.
a) Enums follow scope rules.
b) Enum variables are automatically assigned values. Following is simpler
enum state  {Working, Failed, Freezed};


Comments

Popular posts from this blog

Files in C

A file is a repository of data that is stored in a permanent storage media, mainly in secondary memory. In order to use the files we should learn how to read information from a file and how to write information into a file. A very important concept in C is the stream.The stream is a common logical interface to the various devices( files).A stream is linked to a file while using an open operation. A stream is disassociated from a file while using a close operation. The current location, also referred to as the current position, is the location in a file where the next fie access will occur.There are two types of streams text and binary. The following are some difference between text and binary files ·Text file is human readable because everything is stored in terms of text. In binary file everything is written in terms of 0 and 1, therefore binary file is not human readable. ·A newline(\n) character is converted into the carriage return-linefeed combination before being written to the d…

KTU C programming question paper and evaluation scheme

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY SECOND SEMESTER B.TECH DEGREE EXAMINATION, MAY 2017 CS 100 COMPUTER PROGRAMMING (CS, IT) SCHEME OF EVALUATION
PART A 1 An identifier is a sequence of characters invented by the programmer or to identify or name a specific object. The sequence of characters may be letters, digits, and special character ‘_’known as an underscore Rules: i)Identifiers should start with alphabets. ii)Identifiers are case sensitive iii)A numeric digit should not be the first character iv)Identifier name should not be a keyword v)Identifier may be of any reasonable length 1mark






2mark 2 Associativity defines the direction, left to right or right to left in which operator act upon its operands Unary operators have associativity is from right to left. For examplein the expression &--x, pre decrement works first and then address of operator works Direction + example<

Linear and Binary Search in C

Searching is one of the most common problems that arise in computing. Searching is the algorithmic process of finding a particular item in a collection of items. A search typically answers either True or False as to whether the item is present. On occasion it may be modified to return where the item is found. Search operations are usually carried out on a key field. Consider searching for a given value k in an array A of size n. There are 2 basic approaches: sequential search and binary search.
Linear (Sequential) Search When data items are stored in a collection such as a list or array , we say that they have a linear or sequential relationship. Each data item is stored in a position relative to the others. In C array, these relative positions are the index values of the individual items. Since these index values are ordered, it is possible for us to visit them in sequence. This process gives rise to our first searching technique, the sequential search. Starting at the first item in …