C Tutorial

C Tutorial C Language Environment Setup Execution flow of C program C printf and Scanf C Data type C Token Variable in C Operators in C Comments in C Escape Sequence in C C – Storage Classes C Decision control statement Loop Statement in C Break, continue and goto statement in C Type Casting in C Function in C Recursion in C String in C C Array Pointer in C Dynamic memory allocation C –Structure Nested Structure in C Union in C File Handling in C C pre-processor Static Function In C Sizeof In C Selection Sort In C Scope Of Variables In C Runtime Vs Compile Time In C Random Access Lseek In C Queue Implementation In C Pseudo Code In C Prototype In C Pointer To Pointer In C Pointer Arithmetic In C Passing Array To Function In C Null Character In C Merge Sort In C Macros In C Library Functions In C Memory Leak In C Int In C Goto And Labels In C Fibonacci Series In C Fflush In C Derived Data Types In C Data Types In C Const Vs Volatile In C Character Set In C Character Class Tests In C Calloc In C C Pointers Arrays In C Include In C Clrscr In C C Vs Java String Literals In C Types Of Pointers In C Variables In C Volatile In C Why C Is A Middle Level Language Infix To Postfix Program In C Ceil function in C LCM of two numbers in C Quick sort in C Static in C function pointer as argument in C Top Array Keywords in C Add two numbers using the function in C Armstrong program in C using function Array, Declaring Arrays and Array Initialization Limitations of Inline Function in C Merge and Merge sort with example in C Do-While Loop in C For Loop in C While-Loop in C Difference between while and do-while loop in C Array Of Structures in C Data Structures And Algorithms in C Types Of Structures In C How to Avoid Structure Padding in C Use of Structure in C Do WHILE LOOP in C Programming Examples For Loop in C Programming Examples Entry Control Loop in C Exit control loop in C Infinite loop in C Nested loop in C pow() function in C String Handling functions in C

Variable in C

Variable is an identifier that holds data in memory. It is used to identify input data in a program. The value of the variable can change at the time of executions. Let’s consider the syntax of a variable.

Syntax: Datatype variable_name;
Syntax: Datatype  variable_name1, variable_name2,variable_name3…variable nameN.
We can also declare multiple variables with the same data type by using comma (,). Example:
int a, b; // a and b are variable and int is the data type.
char c; // c is a variable and char is the data type.
Rules for declaring the variable:
  • Variable name should start with alphabets or underscore (_).
  • No space is allowed in a variable while declaration.
  • Variable must not be any reserved word or keyword.
Let’s see some example of how to declare the variables.
Valid declaration  Invalid  declaration
int  b; int 2;
char _name; int  a b;
int a4; int  double;

Types of variables in C.
There are various types of variable in C:
  1. local variable
  2. global variable
  3. static variable
  4. automatic variable
  5. external variable
1. Local variable: A local variable is declared inside of the function or block. It must be declared at the start of the block. Example:
void function1()
{
float x= 34.9; // Here x is local variable.
}
2. Global variable A global variable is declared outside of the function or block. The value of the global variable can be changed.
char name=”ABC”; // global variable
void function1()
{
int x=10; // local variable
}
3. Static variable A static variable is declared with the static keyword. It contains its value during the function call. Example:
void function1(){
int x=5;//local variable will print the same value.
static int y=5; //static variable will print the incremented value like: 5,6,7,...N
x=x+1;
y=y+1;
printf("%d,%d",x,y);
}
4. Automatic variable An automatic variable is declared inside the block. The auto keyword is used to declare the automatic variables.
void main()
{
int a=5;// Here a is local variable or also automatic variable.
auto int b=10;//automatic variable
}
5. External variable An external variable is used to share the multiple C source files by using external variables // save it as abc.h
extern int x=5;  //external variable (also global)
//save as prog1.c
#include "myfile.h"
#include <stdio.h>
void printValue()
{
printf("Global variable: %d", global_variable);
}



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