Category: Variables and Keywords

The sizeof keyword evaluates the size of data (a variable or a constant).

#include <stdio.h>
int main()
{
    printf("%u bytes.",sizeof(char));
}

To learn more, visit C operators.

Output

1 bytes.

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register

The register keyword creates register variables which are much faster than normal variables.

register int var1;

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static

The static keyword creates a static variable. The value of the static variables persists until the end of the program. For example:

static int var;

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struct

The struct keyword is used for declaring a structure. A structure can hold variables of different types under a single name.

struct student{
    char name[80];
     float marks;
     int age;
}s1, s2;

To learn more, visit C structures.

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typedef

The typedef keyword is used to explicitly associate a type with an identifier.

typedef float kg;
kg bear, tiger;

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union

A union is used for grouping different types of variables under a single name.

union student {
    char name[80];
    float marks;
    int age;
}

To learn more, visit C unions.

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void

The void keyword meaning nothing or no value.

void testFunction(int a) {
  .....
}

Here, the testFunction() function cannot return a value because its return type is void.

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volatile

The volatile keyword is used for creating volatile objects. A volatile object can be modified in an unspecified way by the hardware.

const volatile number

Here, number is a volatile object.

Sincenumber is a constant, the program cannot change it. However, hardware can change it since it is a volatile object.

The int keyword is used to declare integer type variables. For example:

int count;

Here, count is an integer variable.

short, long, signed and unsigned

The short, long, signed and unsigned keywords are type modifiers that alter the meaning of a base data type to yield a new type.

short int smallInteger;
long int bigInteger;
signed int normalInteger;
unsigned int positiveInteger;

Data types	Range
short int	-32768 to 32767
long int	-2147483648 to 214743648
signed int	-32768 to 32767
unsigned int	0 to 65535

return

The return keyword terminates the function and returns the value.

int func() {
    int b = 5;
    return b;
}

The goto statement is used to transfer control of the program to the specified label. For example:

for(i=1; i<5; ++i)
{
    if (i==10)
    goto error;
}
printf("i is not 10");
error:
    printf("Error, count cannot be 10.");

Output

Error, count cannot be 10.

The extern keyword declares that a variable or a function has external linkage outside of the file it is declared.

for

There are three types of loops in C programming. The for loop is written in C programming using the keyword for. For example:

for (i=0; i< 9;++i){
  printf("%d ",i);
}

Output

0 1 2 3 4 5 6 7 8

Enumeration types are declared in C programming using keyword enum. For example:

enum suit
{
    hearts;
    spades;
    clubs;
    diamonds;
};

Here, an enumerated variable suit is created having tags: hearts, spades, clubs, and diamonds.

In C programming, if and else are used to make decisions.

if (i == 1)
   printf("i is 1.")
else
   printf("i is not 1.")

If the value of i is other than 1, the output will be :

i is not 1

Keywords double and float are used for declaring floating type variables. For example:

float number;
double longNumber;

Here, number is a single-precision floating type variable whereas, longNumber is a double-precision floating type variable.

char

The char keyword declares a character variable. For example:

char alphabet;

Here, alphabet is a character type variable.

const

An identifier can be declared constant by using the const keyword.

const int a = 5;

do…while

int i;
do 
{
   printf("%d ",i);
   i++;
}
while (i<10)

The switch and case statement is used when a block of statements has to be executed among many blocks. For example:

switch(expression)
{
    case '1':
    //some statements to execute when 1
    break;
    case '5':
    //some statements to execute when 5
    break;
    default:
    //some statements to execute when default;
}

The break statement terminates the innermost loop immediately when it’s encountered. It’s also used to terminate the switch statement.

The continue statement skips the statements after it inside the loop for the iteration.

for (i=1;i<=10;++i){
   if (i==3)
   continue;
   if (i==7)
   break;
   printf("%d ",i);
} 

Output

1 2 4 5 6

When i is equal to 3, the continue statement comes into effect and skips 3. When i is equal to 7, the break statement comes into effect and terminates the for loop. To learn more, visit C break and continue statement