The sizeof keyword evaluates the size of data (a variable or a constant).
#include <stdio.h> int main() { printf("%u bytes.",sizeof(char)); }
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Output
1 bytes.
register
The register keyword creates register variables which are much faster than normal variables.
register int var1;
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;
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;
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typedef
The typedef keyword is used to explicitly associate a type with an identifier.
typedef float kg; kg bear, tiger;
union
A union is used for grouping different types of variables under a single name.
union student { char name[80]; float marks; int age; }
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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.
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.