C Data Types

A data-type in C programming is a set of values and is determined to act on those values. C provides various types of data-types which allow the programmer to select the appropriate type for the variable to set its value.

The data-type in a programming language is the collection of data with values having fixed meaning as well as characteristics. Some of them are an integer, floating point, character, etc. Usually, programming languages specify the range values for given data-type.

C Data Types are used to:

  • Identify the type of a variable when it declared.
  • Identify the type of the return value of a function.
  • Identify the type of a parameter expected by a function.

ANSI C provides three types of data types:

  1. Primary(Built-in) Data Types:
    voidintchardouble and float.
  2. Derived Data Types:
    ArrayReferences, and Pointers.
  3. User Defined Data Types:
    StructureUnion, and Enumeration.

Primary Data Types

Every C compiler supports five primary data types:

voidAs the name suggests, it holds no value and is generally used for specifying the type of function or what it returns. If the function has a void type, it means that the function will not return any value.
intUsed to denote an integer type.
charUsed to denote a character type.
float, doubleUsed to denote a floating point type.
int *, float *, char *Used to denote a pointer type.

Three more data types have been added in C99:

  • _Bool
  • _Complex
  • _Imaginary

Declaration of Primary Data Types with Variable Names

After taking suitable variable names, they need to be assigned with a data type. This is how the data types are used along with variables:Example:

int    age;
char   letter;
float  height, width;

Derived Data Types

C supports three derived data types:

Data TypesDescription
ArraysArrays are sequences of data items having homogeneous values. They have adjacent memory locations to store values.
ReferencesFunction pointers allow referencing functions with a particular signature.
PointersThese are powerful C features which are used to access the memory and deal with their addresses.

User Defined Data Types

C allows the feature called type definition which allows programmers to define their identifier that would represent an existing data type. There are three such types:

Data TypesDescription
StructureIt is a package of variables of different types under a single name. This is done to handle data efficiently. “struct” keyword is used to define a structure.
UnionThese allow storing various data types in the same memory location. Programmers can define a union with different members, but only a single member can contain a value at a given time. It is used for
EnumEnumeration is a special data type that consists of integral constants, and each of them is assigned with a specific name. “enum” keyword is used to define the enumerated data type.

Data Types and Variable Declarations in C


#include <stdio.h>
int main()
    int a = 4000; // positive integer data type
    float b = 5.2324; // float data type
    char c = 'Z'; // char data type
    long d = 41657; // long positive integer data type
    long e = -21556; // long -ve integer data type
    int f = -185; // -ve integer data type
    short g = 130; // short +ve integer data type
    short h = -130; // short -ve integer data type
    double i = 4.1234567890; // double float data type
    float j = -3.55; // float data type

The storage representation and machine instructions differ from machine to machine. sizeof operator can use to get the exact size of a type or a variable on a particular platform.Example:

#include <stdio.h>
#include <limits.h>
int main()
    printf("Storage size for int is: %d \n", sizeof(int));
    printf("Storage size for char is: %d \n", sizeof(char));
    return 0; 
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