Day#2 [ 21 Days — C Programming ]

4 min readOct 5, 2021

Today we will learn variables , keywords and data-types in C , most important we will make out first C Program which is to print “Hello World!!!” .

So be ready with pen and paper and make proper notes so you can revise easily .

If you are not familiar to these don’t worry we will see one by one .

Print “Hello World!!!”

You are familiar with this code except 3rd line .

Line-3 : printf is a function and it is used to show output . Whatever you want to print write in printf with double quote .

Example:

printf(“Tick-Tick”) -> It will show Tick-Tick to the console/Output.

All functions are defined in particular header file . printf function is defined in “stdio.h” header file , So if you don’t include “stdio.h” it will give you error that printf function is not defined .

We will see more header files and their functions .

Assignment : Print your name .

you can try to print more things like .

“\n” is used to move cursor in new line , try yourself by using \n at different places and see the results .

Variables and Datatypes in C

Variable is the name given to a memory location . It store the value and we can modify value .

Since value can be your name, your age or any number so there are different-different datatypes which defines the types of variables . So let’s see datatypes used in C Programming -

int : Store Numeric Value
char : Store Character
float : Store Floating value with single precision
double : Store Floating value with double precision

So let’s see some variables -

int a = 2;
float b = 3.14;
char c = ‘A’;
double d = 22.12;

Keywords in C

Keywords are reserved words that you can’t use in your program for any other purpose because they are defined for specific purpose .

There are total 32 keywords in C .

Here is a list of Keywords -

auto
break
case
char
const
continue
default
do
double
else
enum
extern
float
for
goto
if
int
long
register
return
short
signed
sizeof
static
struct
switch
typedef
union
unsigned
void
volatile
while

Print Variables

Previously we have printed Hello World!!!, name etc.

we use special format specifiers to print variables which starts with % and then type of variables .

Here are format specifiers -

int : %d
float : %f
char : %c;
double : %lf
long : %ld
long long : %lld
long double : %Lf
octal : %o
hexadecimal : %x
unsigned int : %u

printf(“c =%c\nf = %f”,c,f); first %c will be replaced by value of c and second %f will be replaced by the value of variable f.

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