Keywords in C Programming
Description of all Keywords in C
auto
- auto is used to define a variable of storage class automatic. For example:
auto int var1;
- This statement suggests that var1 is an auto-storage class variable and int-type data. Variables declared within feature bodies are default automatic.
- Every time a task is executed, they are recreated. Since automatic variables are local to a function, local variables are also called automatic variables.
break and continue
- The break statement is used to jump out of the innermost enclosing loop (while, do, for or switch statements) explicitly and pass control to next statement immediately following the loop.
- In other hand, continue statement is used to skip certain statements inside the loop.
for (i=1;i<=10;++i){
if (i==3)
continue;
if (i==7)
break;
printf("%d ",i);
}
The output of the given code is:
1 2 4 5 6
- It is because, when i=3, continue statement comes to effect and skips 3 and when i=7, break statements come to effect and terminates the loop.
switch, case and default
- The switch statement tests the value of a expression and test with the different "case" values. We can use "default" value, if it doesn't matches any of "case" values. For example:
switch(option){
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;
}
char
- The char keyword is used for indicating the variable is of the type character. For example:
char variable0;
Here, variable0 is a variable of type character.
const
const makes the value of a pointer or a variable unmodified.
const int a=5;
In this example, a is the constant and its value is 5. This value cannot be changed in program.
do and while
while and do are used for looping in C. For example:
i=2;
while (i<10) {
print("%d ",i)
i++;
}
Output of the program
2 3 4 5 6 7 8 9.
If programmer finds easy to write statements to be executed before writing test condition, do...while loop is used.
int i;
do {
print("%d ",i);
i++;
}
while (i<10)
double and float
- double and float are used for indicating floating type variables. Keywords float and double represents single precision and double precision floating point data respectively. For example:
float variable1;
double variable2;
Here, variable1 is single precision floating type variable whereas, variable2 is a double precision floating type variable.
if and else
- if and else are used in decision making in C.
if (i==1)
printf("i is 1.")
else
prinf("i is not 1.")
If value of i is other than 1, output will be :
i is not 1
enum
- enum is used to define enumerated type data type. Enumerated data type creates a set of constant of type int. For example:
enum enum_var{
var1;
var2;
var3;
};
- Here, a enumerated variable enum_var is created having tags: var1, var2 and var3.
extern
- Keyword extern is used for indicating the variable is external and is declared outside every function and can be accessed by any function. For example:
#include <stdio.h>
extern i=5;
void print1(){
printf ("%d ",i);
}
int main() {
printf("%d ",i);
}
return 0;
}
Output of the given code is:
5 5
for
- Keyword for is used for looping in C. For example:
for (i=0;i<9;++i){
printf("%d ",i);
}
Output of the code given:
0 1 2 3 4 5 6 7 8
goto
- Keyword goto is used for unconditional jump to a labeled statement inside that function. For example:
for(i=1;i<5;++i){
if (i==10)
goto error;
}
printf("i is not 10");
error:
printf("Error, count can't be 10");
Output of the given code: 1 2 3 4 5 6 7 8 9 10
int
- int is used for indicating the variable is of type integer.
int var0;
Here, var0 is a variable of type integer.
short, long, signed and unsigned
- short, long, signed and unsigned are type modifiers that alters the meaning of base data type to yield new type.
short int var1;
long int var2;
signed int var3;
unsigned int var4;
Here, the int type variable is modified to short int, long int, signed int and unsigned int respectively.
Range of int type data types
- Datatypes Range
- short int -32768 to 32767
- long int -2147483648 to 214743648
- signed int -32768 to 32767
- unsigned int 0 to 65535
return
- Keyword return terminates the execution of current function and returns the value to the calling function.
int func(){
int b=5;
return b;
}
This function func() returns 5 to to the calling function.
sizeof
- sizeof is used to find the number of bytes of an object.
#include <stdio.h>
int main(){
printf("%u bytes.",sizeof(char));
}
Output of the given code:
1 bytes.
Here, sizeof(...) is used to find the number of bytes of type char.
register
- Variable of storage class register are much faster than normal variables.
register int var1;
- Here, var1 is the variable of storage class register.
static
- static is used for indicating the variable is of storage class static. The value of the static variables persists until the end of the program. For example:
static int var;
- Here, var is a variable of storage class static.
struct
- struct is used in creating a structure which provide means to group different types of variable under one name for easier handling.
struct student{
char name[80];
float marks;
int age;
}s1,s2;
Here, struct keyword is used in creating a structure of tag name student and variables of type "struct student".
typedef
- Keyword typedef is used to explicitly associate a type with an identifier.
typedef float kg;
kg bear,tiger;
- Here, the use of typedef is to create a type kg and this kg type is used in declaring variables bearand tiger.
union
- Union is used in creating a union which provide means to group different types of variable under one name for easier handling.
union student {
char name[80];
float marks;
int age;
}
Here, union keyword is used in creating a union of tag name student and variables of type "union student".
void
- void is used to indicate that a function takes no arguments or returns no value.
void no_return(int a){
.....
}
Here, function no_return( ) can take value but, can't return value because, the return type is void.
volatile
- volatile is used to create a volatile object. A volatile object can be modified in unspecified way by the hardware.
const volatile number
- Here, number is a volatile object. Since, number is constant variable, program can't change it but, hardware can change it because, it is a volatile object.
auto
- auto is used to define a variable of storage class automatic. For example:
auto int var1;
- This statement suggests that var1 is an auto-storage class variable and int-type data. Variables declared within feature bodies are default automatic.
- Every time a task is executed, they are recreated. Since automatic variables are local to a function, local variables are also called automatic variables.
break and continue
- The break statement is used to jump out of the innermost enclosing loop (while, do, for or switch statements) explicitly and pass control to next statement immediately following the loop.
- In other hand, continue statement is used to skip certain statements inside the loop.
for (i=1;i<=10;++i){
if (i==3)
continue;
if (i==7)
break;
printf("%d ",i);
}
The output of the given code is:
1 2 4 5 6
- It is because, when i=3, continue statement comes to effect and skips 3 and when i=7, break statements come to effect and terminates the loop.
switch, case and default
- The switch statement tests the value of a expression and test with the different "case" values. We can use "default" value, if it doesn't matches any of "case" values. For example:
switch(option){
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;
}
char
- The char keyword is used for indicating the variable is of the type character. For example:
char variable0;
Here, variable0 is a variable of type character.
const
const makes the value of a pointer or a variable unmodified.
const int a=5;
In this example, a is the constant and its value is 5. This value cannot be changed in program.
do and while
while and do are used for looping in C. For example:
i=2;
while (i<10) {
print("%d ",i)
i++;
}
Output of the program
2 3 4 5 6 7 8 9.
If programmer finds easy to write statements to be executed before writing test condition, do...while loop is used.
int i;
do {
print("%d ",i);
i++;
}
while (i<10)
double and float
- double and float are used for indicating floating type variables. Keywords float and double represents single precision and double precision floating point data respectively. For example:
float variable1;
double variable2;
Here, variable1 is single precision floating type variable whereas, variable2 is a double precision floating type variable.
if and else
- if and else are used in decision making in C.
if (i==1)
printf("i is 1.")
else
prinf("i is not 1.")
If value of i is other than 1, output will be :
i is not 1
enum
- enum is used to define enumerated type data type. Enumerated data type creates a set of constant of type int. For example:
enum enum_var{
var1;
var2;
var3;
};
- Here, a enumerated variable enum_var is created having tags: var1, var2 and var3.
extern
- Keyword extern is used for indicating the variable is external and is declared outside every function and can be accessed by any function. For example:
#include <stdio.h>
extern i=5;
void print1(){
printf ("%d ",i);
}
int main() {
printf("%d ",i);
}
return 0;
}
Output of the given code is:
5 5
for
- Keyword for is used for looping in C. For example:
for (i=0;i<9;++i){
printf("%d ",i);
}
Output of the code given:
0 1 2 3 4 5 6 7 8
goto
- Keyword goto is used for unconditional jump to a labeled statement inside that function. For example:
for(i=1;i<5;++i){
if (i==10)
goto error;
}
printf("i is not 10");
error:
printf("Error, count can't be 10");
Output of the given code: 1 2 3 4 5 6 7 8 9 10
int
- int is used for indicating the variable is of type integer.
int var0;
Here, var0 is a variable of type integer.
short, long, signed and unsigned
- short, long, signed and unsigned are type modifiers that alters the meaning of base data type to yield new type.
short int var1;
long int var2;
signed int var3;
unsigned int var4;
Here, the int type variable is modified to short int, long int, signed int and unsigned int respectively.
Range of int type data types
- Datatypes Range
- short int -32768 to 32767
- long int -2147483648 to 214743648
- signed int -32768 to 32767
- unsigned int 0 to 65535
return
- Keyword return terminates the execution of current function and returns the value to the calling function.
int func(){
int b=5;
return b;
}
This function func() returns 5 to to the calling function.
sizeof
- sizeof is used to find the number of bytes of an object.
#include <stdio.h>
int main(){
printf("%u bytes.",sizeof(char));
}
Output of the given code:
1 bytes.
Here, sizeof(...) is used to find the number of bytes of type char.
register
- Variable of storage class register are much faster than normal variables.
register int var1;
- Here, var1 is the variable of storage class register.
static
- static is used for indicating the variable is of storage class static. The value of the static variables persists until the end of the program. For example:
static int var;
- Here, var is a variable of storage class static.
struct
- struct is used in creating a structure which provide means to group different types of variable under one name for easier handling.
struct student{
char name[80];
float marks;
int age;
}s1,s2;
Here, struct keyword is used in creating a structure of tag name student and variables of type "struct student".
typedef
- Keyword typedef is used to explicitly associate a type with an identifier.
typedef float kg;
kg bear,tiger;
- Here, the use of typedef is to create a type kg and this kg type is used in declaring variables bearand tiger.
union
- Union is used in creating a union which provide means to group different types of variable under one name for easier handling.
union student {
char name[80];
float marks;
int age;
}
Here, union keyword is used in creating a union of tag name student and variables of type "union student".
void
- void is used to indicate that a function takes no arguments or returns no value.
void no_return(int a){
.....
}
Here, function no_return( ) can take value but, can't return value because, the return type is void.
volatile
- volatile is used to create a volatile object. A volatile object can be modified in unspecified way by the hardware.
const volatile number
- Here, number is a volatile object. Since, number is constant variable, program can't change it but, hardware can change it because, it is a volatile object.
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