Variables :
A variable is a Container which stores a 'Value'. like In Kitchen, we have containers storing Rice, Wheat, Sugar etc. Similar to that Variables in C Stores value of a Constant
e.g.
int a=3; // a is integer and assigned as '3'
float b=3.5 // b is Real No. which is assigned as '3.5'
char x='A' // x is a Characters which is assigned to 'A'
Rules for naming variables in C :
➔ First Character must be an alphabet or underscore(_)
➔ No Commas, blanks allowed
➔ No Special Symbol other than (_) allowed.
➔ Variable names are case sensitive
➔ We must create meaningful variable names in our programs. This enhances readability
of our program
Constants :
➔ An entity whose value doesn't change is called as a constant.
➔ A Variable is an entity whose value can be changed.
Types of Constant :
➔ Integer Constant ➟ 12, -2, 5, 8
➔ Real Constant ➟ 23.5, -423.32, 7.0
➔ Character constant ➟ 'a', '$' (Must be enclose within single quotes)
Keywords :
These are reserved words, whose meaning is already known to the Compiler.
There are 32 keywords available in C :
auto double int struct
break long else switch
case return enum typedef
char register extern union
const short float unsigned
continue signed for void
default sizeof goto volatile
do static if while
Basic Structure of a C Program ➟
➔ All C programs have to follow a basic structure.
➔ A C program starts with a main function and executes instructions present inside it
➔ Each instruction is terminated with a semicolon(;)
Some rules which are applicable to all the C programs ➟
➔ Every program execution starts from main() function
➔ All the statements are terminated with a semicolon
➔ Instruction are Case-Sensitive
➔ Instruction are executed in the same order in which they are written
Comments ➟
➔ Comments are used to clarify something about the program in plain language.
It is a way for us to add notes to our program.
➔ Comments in a program are not executed and are ignored.
There are two types of comment :
➔ Single line comment :
// This is Single Line Comment
➔ Multi-line Comments :
/* This is Multi-Line
Comment */
Compilation and Execution :
A complier is a computer program which converts a C program into machine language so that it can be easily understood by the Computer.
A C program is written in plain text.
This plain text is combination of Instruction in a particular sequence. The compiler performs some basics checks and converts the program into an executable.
first.c ➔ C Compiler ➔ first.exe
program in VS Code (with gcc it compile the program) (gives output )
Library Functions :
C language has a lot of valuable library functions which is used to carry out certain
tasks for instance printf function is used to print value on the screen
syntax : printf("This is %d", i);
➔ %d for integers
➔ %f for real numbers
➔ %c for character
Types of variable :
➔ Integer variables ➟ int a = 3 ;
➔ Real variables ➟ float a = 5.3 ;
➔ Character variable ➟ char a = 'A' ;
Syntax :
# include<stdio.h>
// Lets learn about Variables in C Programming Language
int main(){
int age = 22 ; // integer variable
int class = 12 ;
printf("Hey Dude! I'm %d Years old \n", age);
printf("and I'm in class : %d", class);
return 0; }
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