Data Type Tutorials

For java Tutorial log on to myjavaquestionbank.blogspot.in                                  Introducing C data type

Every programming language deals with some data. For example to print any message it requires charterer or string type of data. To solve any mathematic expression it requires integral as well as real number (floating type) of data. C is very rich in data type. We can broadly divide all data type in c in three categories:

1. Primitive or fundamental data type

2. Derived data type

3. User defined data type

List of data type in c

A complete picture of all c data types has been represented by following figure.

Note: Apart from these basic data type there are few other data types which have been defined inside header files which will be discussed later. 

C data type modifiers

There are some keywords in c which modify the meaning the meaning of above mentioned basic data type in c. On the basis of properties of modifier we can categories the modifier in following eight groups.

1. Size modifier

2. Signed modifier

3. Constant modifier

4. Volatile modifier

5. Storage class

6. Pointer modifier

7. Function modifier

8. Interrupt

All modifiers in c have been represented by following table:

In the above table modifier ending with * indicates they are not keyword of c language. These modifiers are called as nothing modifier since there is not any special keyword in which represents those modifiers. If you will not write any thing it then compiler will understand you are writing nothing modifier of those groups.

Meaning of following word in the above table:

nothing: It is not short as well as not long.

not_const:  It is not constant. You can modify.

Not_volatile: It is not volatile.

not_interrupt: It is not sending interrupt signal.

Important points:

1. Nothing modifier must be default modifier of that group.

2. In LINUX GCC compiler there is not any concept of pointer modifier.

Default modifier in c

    If you will not write any modifiers of a particular group then c compiler will take default modifier of that group. Default modifier of each group has written in the following table:

 

1. Default modifier of storage class is auto when we declared the variable inside any function and default modifier of storage class is static when we declared variable outside of all functions. In other word we can say if variable has declared locally then default storage class is auto and if it has declared globally then default storage class of variable is extern.

2. Default storage class of function is extern.

3. Default modifier of pointer modifier depends upon memory model. For detail knowledge click following link:

WHAT IS MEMORY MODEL IN C?

Modifiers in c

Explanation of modifiers in c programming language by examples and questions

Rules for using modifier in c

Rule 1: We cannot use two modifiers of same groups in any particular data type of c.

For example, following declaration of c are illegal:

short long int i;

static auto char c;

signed unsigned int array[5];

pascal cdecl display();

Following are valid declaration of c:

const volatile float f;

signed static long volatile int i;

Question: Is following declaration is valid in c?

1.   intnear * far * huge *p;

2.  char const * const *c;

3.  short short int i;

4.  const const int i;

Rule 2: We can write modifier either before the data type or after the data type. For example, both of following declaration is correct:

unsigned char c;

char unsigned c;

Rule 3: Order of modifier including data type doesn’t affect the meaning of declaration. For example all of the following have same meaning:

int const short extern i;

int extern const short i;

int short extern const i;

const int short extern i;

extern short const int i;

Rule 4: There is one exception in rule 3. POINTER, FUNCTION and INTERRUPT modifier must be written after the data type. For example, in the following declaration:

unsigned const char far *c;

char unsigned const *c;

char far unsigned const *c;

const char far unsigned *c;

far char const unsigned *c;

const unsigned far char *c;

First four declarations are valid as well as equivalent. But last two declarations are invalid.

Range of data types in c

Following table illustrate the range or maximum or minimum value of data types in TURBO C++ and Borland c++ compilers.  

 

Note: In the above table range of float, double and long double has written only for positive numbers. But this range is also true for negative numbers i.e. for range of float is -3.4*10^38 to -3.4*10^ (-38) and so on.

 

Interview Question: Why range of signed char is -128 to 127 not -127 to 128?

const modifier in c

Explanation of const modifier in c programming language by examples, questions and answers:

In c all variables are by default not constant. Hence, you can modify the value of variable by program. You can convert any variable as a constant variable by using modifier const which is keyword of c language.

Properties of constant variable:

1. You can assign the value to the constant variables only at the time of declaration. For example:

const int i=10;

float const f=0.0f;

unsigned const long double ld=3.14L;

2. Uninitialized constant variable is not cause of any compilation error. But you cannot assign any value after the declaration. For example:

const int i;

If you have declared the uninitialized variable globally then default initial value will be zero in case of integral data type and null in case of non-integral data type. If you have declared the uninitialized const variable locally then default initial value will be garbage.

3. Constant variables executes faster than not constant variables.

4. You can modify constant variable with the help of pointers. For example:

#include

int main(){

    int i=10;

    int *ptr=&i;

    *ptr=(int *)20;

    printf("%d",i);

    return 0;

}

Output: 20