C Keywords
keyword is predefined reserved word. this are defined by compiler and this are used to special purpose. this are used to declare variables, conditional statement, function statement, user defined data type etc. So that is very important is how to use keyword in our source code. In this post we are learn about how to use keyword in c programming language.
Description of c keywords
There is supported total 32 keywords. there are as follows.
int
int is data type. integer variable are capable to store the value of 2 bytes for 32 bit compiler ,and 4 bytes of 64 bit compiler. declare integer variables as follows.
int variable_list;int : keyword
variable_list : variable name
/*
Example to use int keyword
*/
/*Header file*/
#include <stdio.h>
/*
int : keyword
global : variable name
*/
int global=12;
int main(){
/*
int : keyword
local : variable name
*/
int local=10;
printf("\n Global : %d ",global);
printf("\n Local : %d ",local);
return 0;
}Output:
Global : 12
Local : 10 int keyword also use when function return integer value
float
float is an data type of c programming language.
/*
Example to use float keyword
*/
/*Header file*/
#include <stdio.h>
//function declaration
float sum(float no1,float no2);
//return sum of two float numbers
float sum(float no1,float no2){
return no1+no2;
}
int main(){
//float variables
float num1=12.0f,num2=10.0f;
printf("Sum of [%f + %f] is : %f",num1,num2,sum(num1,num2));
return 0;
}
Output
Sum of [12.000000 + 10.000000] is : 22.000000char
char is an data type. compiler is allocate one byte memory of character variables.
/*
Example to use char keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
//char variables
char capital_a='A',small_a='a';
printf("Value of capital_a is : %c ASCII [%d]\n",capital_a,capital_a);
printf("Value of small_a is : %c ASCII [%d]\n",small_a,small_a);
return 0;
}
Value of capital_a is : A ASCII [65]
Value of small_a is : a ASCII [97]
double
double is an data type.
/*
Example to use double keyword
*/
/*Header file*/
#include <stdio.h>
//function declaration
double salary(int);
double salary(int days){
double count=1000;//per day
return days*count;//return double value
}
int main(){
int day=10;
//double variable
double money=salary(day);
printf("Joy is works %d day their salary is %lf ",day,money);
return 0;
}
Output
Joy is works 10 day their salary is 10000.000000long
/*
Example to use long keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
//long keyword use before int and double
long int number=10;
long double dbl_value=123.33;
printf("long int number : %ld\n",number);
printf("long double dbl_value : %Lf\n",dbl_value);
return 0;
}Output:
long int number : 10
long int dbl_value : 123.330000
signed
/*
Example to use signed keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
//signed keyword use before int
signed int ivar=10;
printf("signed int ivar : %d\n",ivar);
return 0;
}Output:
signed int ivar : 10unsigned
/*
Example to use unsigned keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
//unsigned keyword
unsigned int postive_int=10;
printf("unsigned int postive_int: %i\n",postive_int);
return 0;
}Output:
unsigned int postive_int: 10short
/*
Example to use short keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
//short keyword
short int month=10;
printf("short int month: %d\n",month);
return 0;
}Output:
short int month: 10const
/*
Example to use const keyword
*/
/*Header file*/
#include <stdio.h>
//constant PI variable
const float PI=3.14159265;
int main(){
//constant max_month int variable
const int max_month=12;
printf("Value of PI : %f\n",PI);
printf("Value of max_month : %d",max_month);
return 0;
}Output:
Value of PI : 3.141593
Value of max_month : 12do
/*
Example to use do keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
int month=1;
//do is keyword
do{
printf("%d\n",month);//print month value
month++;
}while(month<=12);//terminate condition
return 0;
}Output:
1
2
3
4
5
6
7
8
9
10
11
12while
/*
Example to use while keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
int counter=1;
//while is keyword
while(counter<=5){
printf("counter : %d\n",counter);
counter++;
}
return 0;
}Output:
counter : 1
counter : 2
counter : 3
counter : 4
counter : 5
for
/*
Example to use for keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
//for is keyword
for(int i=1;i<=10;i++){
printf("%d\n",i*2);//print
}
return 0;
}Output:
2
4
6
8
10
12
14
16
18
20
if
/*
Example to use if keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
if(10>5){
printf("10 is greater than 5");
}
return 0;
}Output:
10 is greater than 5else
/*
Example to use else keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
if(10>15){
printf("10 is greater than 15");
}else{
printf("10 is less then 15");
}
return 0;
}Output:
10 is less then 15continue
/*
Example to use continue keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
int status=8;
for(int i=1;i<status;i++){
if(i==3||i==5) continue;//continue statement
printf("%d\n",i);
}
return 0;
}Output:
1
2
4
6
7break
break statement are use inside a loop and switch case. that are stop the execution of loop and switch case.
/*
Example to use break keyword
*/
/*Header file*/
#include <stdio.h>
int main(){
int i=1;
for(i;;i++){
printf("%d\n",i);
if(i==4){
break;//break statement
}
}
switch(i){
case 1:
printf("Case 1 execute\n");
break;//break statement
case 3:
printf("Case 3 execute\n");
break;
case 4:
printf("Case 4 execute\n");
break;
default:
printf("Missing case\n");
}
return 0;
}Output:
1
2
3
4
Case 4 executeswitch
/*
Example to use switch keyword
*/
/*Header file*/
#include <stdio.h>
//function declaration
void message(int,int,int);
void sum(int,int);
void sub(int,int);
void mul(int,int);
void sum(int value1,int value2){
printf("Sum [%d + %d] is : %d\n",value1,value2,value1+value2);
}
void sub(int value1,int value2){
printf("Sub [%d - %d] is : %d\n",value1,value2,value1-value2);
}
void mul(int value1,int value2){
printf("Mul [%d * %d] is : %d\n",value1,value2,value1*value2);
}
void message(int i,int num1,int num2){
//switch case
switch(i){
case 1:
sum(num1,num2);
break;
case 2:
sub(num1,num2);
break;
case 3:
mul(num1,num2);
break;
default:
printf("Invalid option\n");
}
}
int main(){
message(1,5,2);
message(3,5,4);
message(5,2,3);
return 0;
}Output:
Sum [5 + 2] is : 7
Mul [5 * 4] is : 20
Invalid option
default
/*
Example to use default keyword
*/
/*Header file*/
#include <stdio.h>
void task(int info){
switch(info){
case 1:
printf("value is 1\n");
break;
//default
default :
printf("This is default case value is: %d\n",info);
}
}
int main(){
task(1);
task(3);
return 0;
}Output:
value is 1
This is default case value is: 3sizeof
/*
Example to use sizeof
*/
/*Header file*/
#include <stdio.h>
int main(){
printf("size of int : %zu\n",sizeof(int));
printf("size of char : %zu\n",sizeof(char));
printf("size of float : %zu\n",sizeof(float));
printf("size of double : %zu\n",sizeof(double));
return 0;
}Output:
size of int : 4
size of char : 1
size of float : 4
size of double : 8
union
/*
Example to use union
*/
/*Header file*/
#include <stdio.h>
int main(){
union Employee{
int id,age;
double salary;
};
union Employee s1;
//basic example to print size of union
printf("sizeof union Employee s1 : %zu",sizeof(s1));
return 0;
}Output:
sizeof union Employee s1 : 8enum
/*
Example to use enum
*/
/*Header file*/
#include <stdio.h>
enum weekDay{mon=1, tue, wed, thur, fri, sat, sun};
int main(){
int i=0;
for(i=mon;i<=sun;i++){
printf("day : %d\n",i);
}
return 0;
}Output:
day : 1
day : 2
day : 3
day : 4
day : 5
day : 6
day : 7
struct
/*
Example to use struct
*/
/*Header file*/
#include <stdio.h>
//define structure of book
struct Book{
int pages;
float price,weight;
};
int main(){
//start execution
struct Book b1,b2;
b1.pages=200;
b1.price=500.24;
b1.weight=450;
b2.pages=100;
b2.price=300.34;
b2.weight=350;
printf("Book b1 info\n");
printf("Pages %d\n",b1.pages );
printf("Weight %f\n",b1.weight );
printf("price %f\n",b1.price );
printf("\nBook b2 info\n");
printf("Pages %d\n",b2.pages );
printf("Weight %f\n",b2.weight );
printf("price %f\n",b2.price );
return 0;
}Output:
Book b1 info
Pages 200
Weight 450.000000
price 500.239990
Book b2 info
Pages 100
Weight 350.000000
price 300.339996typedef
/*
Example to use typedef
*/
/*Header file*/
#include <stdio.h>
//define structure of book
typedef struct Book{
int pages;
float price,weight;
}bookinfo;
int main(){
//start execution
bookinfo b1,b2;
b1.pages=20;
b1.price=60.24;
b1.weight=250;
b2.pages=100;
b2.price=300.34;
b2.weight=350;
printf("Book b1 info\n");
printf("Pages %d\n",b1.pages );
printf("Weight %f\n",b1.weight );
printf("price %f\n",b1.price );
printf("\nBook b2 info\n");
printf("Pages %d\n",b2.pages );
printf("Weight %f\n",b2.weight );
printf("price %f\n",b2.price );
return 0;
}Output:
Book b1 info
Pages 20
Weight 250.000000
price 60.240002
Book b2 info
Pages 100
Weight 350.000000
price 300.339996
auto
/*
Example to use auto
*/
/*Header file*/
#include <stdio.h>
int main(){
//auto storage class
auto int value= 10;
printf("Value : %d",value);
return 0;
}Output:
Value : 10register
/*
Example to use register
*/
/*Header file*/
#include <stdio.h>
int main(){
//register storage class
register int value= 10;
printf("Value : %d",value);
return 0;
}Output:
Value : 10extern
/*
Example to use extern
*/
/*Header file*/
#include <stdio.h>
int main(){
//extern storage class
extern int no1,no2;
printf("no1 : %d\n",no1);
printf("no2 : %d\n",no2);
return 0;
}
int no1=10,no2=12;Output:
no1 : 10
no2 : 12
static
/*
Example to use static
*/
/*Header file*/
#include <stdio.h>
void func_call(){
static int status=1;
printf("status : %d\n",status);
status++;
}
int main(){
//calling function
func_call();
func_call();
return 0;
}Output:
status : 1
status : 2
goto
goto statement is a jump statement. there are capable to change the execution flow within program. look at view this example.
/*
Example to use goto
*/
/*Header file*/
#include <stdio.h>
int main(){
//start execution of program
int num=1;
lable:
printf("%d\n",num);
num++;
//condition
if(num<5)
goto lable;//goto level
return 0;
}Output:
1
2
3
4
return
/*
Example to use return
*/
/*Header file*/
#include <stdio.h>
//function declaration
int sum(int ,int );
int sum(int no1,int no2){
return no1+no2;// return sum of two number
}
int main(){
//start execution of program
int num1=3,num2=10;
printf("\nSum is : %d",sum(num1,num2));
return 0;
}Output:
Sum is : 13volatile
volatile is a qualifiers that is applied to c variable when declared variable. compiler and understand that behaviour. the volatile variable are change at any time without any action required. look at view this example we are change constant variable value.
/*
Example of volatile
*/
/*Header file*/
#include <stdio.h>
int main(){
const volatile int num=10;
//typecast then assign const volatile variable address
int *ptr=(int*)&num ;
printf("\n Num is : %d",num);
*ptr=12;
printf("\n*ptr : %d",*ptr);
return 0;
}Output:
Num is : 10
*ptr : 12void
void is data type there are use in following situations.
1) when function are not returning any value.
2) when function are not accept any arguments.
3) using pointer data type
Example:
/*
Example of void
*/
/*Header file*/
#include <stdio.h>
//function declaration
void info(int);
void message(void);
//in this case void are use function return type
void info(int num){
printf("Value of num is : %d\n",num);
}
//in this case void are use function return type and paramter list
void message(void){
printf("Hello programmers\n");
}
int main(){
message();
int num=10;
info(num);
void *ptr=&num ;
printf("Value of void *ptr : %d\n",*((int*)ptr));
return 0;
}Output:
Hello programmers
Value of num is : 10
Value of void *ptr : 10
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