**C Instructions With Examples**

I hope before continuing to this tutorial you must have
written the basic printf() and scanf() programs. If you didn’t then I strongly
recommend you to do it. Read previous tutorials from here.

Anyways so far we have covered the very basic programs of C.
We have used many instructions in it. So today I will tell you about the C
instructions.

**What are C Instructions?**

There are basically three types of C instructions.

1. Type Declaration Instruction

2. Arithmetic Instruction

3. Control Instruction

We have covered first two types of instructions already in
our previous turorials but I will tell you about certain nuances of these
instructions now. So lets try to analyse them one by one.

**Type Declaration Instruction**

As its name suggests it is used to declare type of variables
in C language. It is must that you have to declare the type of variable before
using it. And it is also must that these type declaration instruction should be
provided in the beginning of the program (just after the main()).

Now lets learn about some variations in them.

a) We can initialize the variable at the time of its
declaration.

Example

int a=3;

char a=’d’;

int a=7*3*2;

b) Remember the order of variables while declaring them.

**Example**

int i=3,j=5; is same as int j=5,i=3;

However,

float a=5.5,b=a+7.1; is alright, but

float b=a+7.1,a=5.5; is not valid.

It is because in the above declaration we are trying to use
variable a even before defining it.

**c) Another interesting point while declaring variables is**

Below instruction will work

int a,b,c,d;

a=b=c=10;

However, the following statement would not work.

int a=b=c=d=10 ;

Now again we are trying to use variables even before
defining them.

I hope now you must have understand the importance of type
declaration instruction. So we can only use variables after defining them. And
these definition should be written at the starting of main() body. We cannot
define variables anywhere else in the program. If you do so, it will result in
an error.

**Arithmetic Instruction**

General form of an arithmetic instruction follow rules given
below.

i) It should contain one assignment operator i.e. =.

ii) On the left side of =, there should be one variable.

iii) On the right side of =, there should be variables and
constants.

iv) And those variables and constant will be connected by
some arithmetic operators like +,-,*,/,%.

**Example**

int a=12;

float b,c=2.2;

b=c+a/6.1*8;

**What are operands?**

These variables and constants together are called operands.
These operands are connected by arithmetic operators.

How the execution of arithmetic instructions takes place?

Firstly all the variables and constants on the right hand
side of assignment operator (=) is calculated. After that the result will be
stored in the variable on the left hand side of assignment operator.

Now let’s checkout certain nuances of arithmetic operators

1. It is compulsory to use only one variable on the left
hand side of =.

Example

c=a*b is correct,

whereas a*b=c is incorrect.

2. A operator named modular operator (%) is also used in C.
This modular operator will return the remainder to left hand side variable of
assignment operator. It cannot be used with floats. It will return the same
sign as the numerator has.

**Example**

-5%2=-1

5 %-2=1

**Control Instruction**

This instruction is used to shift the control of program as
per the user or programmer wants. This instruction contains decision making,
looping and more. This is a bit advance topic. We will cover this topic in our
later tutorials.