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INTRODUCTION TO PROGRAMMING

I am collating my study notes as part of my education into Computer Programming. In an attempt to increase and improce my own learning, and to help others also (learn by teaching) I will be sharing my notes, as neatly presented as possible, for others to follow along with if they so wish. This is Lesson 3's notes.

EARLIER LESSONS

Lesson 1 Notes
Lesson 2 Notes

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INTRODUCTION TO COMPUTER PROGRAMMING – STUDY NOTES

LESSON 3

OPERATORS

LINK: Operators

Operators allow you to operate on an element of the program.

Assignment

=
This means to apply the value of. For example x = y means to apply the value of x to y. It is not the same meaning as standard mathematics where it means equal to.

Arithmetic Operators

+Addition
-Subtraction
*Multiplication
/Division
%Modulo

Modulo = remainder of a division operation.

Example 143 / 3 = 47.66 (standard division) but if you take only the whole numbers, then the modulo of that operation is 143 / 3 = 47, WITH a remainder of 2. In other words, 47 * 3 = 141 and the difference between 143 and 141 is 2 (This is the modulo, or the remainder). There is a need for such an operator within programming languages.

Compound Operators

+= : x+=y is the same as saying x=x+y
-+ : x-=y is the same as saying x=x-y
*+ : x=y is the same as saying x=xy
/= : x/=y is the same as saying x=x/y
%= : x%=y is the same as saying x=x%y

This allows for a slightly shorter way of writing out these operators.

Unary Operators

++ : X++ is the same as saying x=x+1 (used a lot in loops)
-- : X-- is the same as saying x=x-1 (used a lot in loops)
! : Means NOT.
Example : x=true, then !x would then be false (ie - NOT true)

Prefix Operator vs Suffix Operator

LINK: Increment and Decrement Operators

When the ++ or -- is set as a prefix as opposed to a suffix like earlier described, then the value of the variable that it relates to is handled differently. The variable is increased FIRST then assigned to the new variable.

Prefix Example:
x = 3
y = ++x
In this example x is assigned (=) the value of 3, and then because of the PREFIX in the second line, x is increased by 1 to 4 (++x) BEFORE y is assigned that value. Now both x and y have the value of 4.

The suffix example would create a different answer.

Suffix Example
x = 3
y = x++
In this example x is assigned (=) the value of 3, and then because of the SUFFIX in the second line, x is increased by 1 to 4 (x++) AFTER y is assigned that value. So y is assigned the value of x which is 3, THEN x is increased by 1 to 4.

This seemingly minor but significant difference can lead to logical errors in your program if you apply the wrong use of suffix/prefix.

Suffix = value is assigned first before it is increased.
Prefix = value is increased first before it is assigned.

Relational/Comparison Operator

Used to compare 2 values.
Will always evaluate to a Boolean value (TRUE or FALSE).

== : equal to
!= : not equal to
> : greater than
< : less than
>= : greater than or equal to
<= : less than or equal to

- Logical Operator

Used to tell the computer to do an operation when certain conditions or mix of conditions are met. Such as condition 1 AND condition 2; condition 1 OR condition 2. Also the NOT operator.

! : NOT :
&& : AND : True only when both conditions are true.
|| : OR : True if one or the other is true.

Operator Precedence

There is an order to which operators are evaluated. There is an order of importance.
All the languages use the same precedence.

LINK: C++ Example
LINK: JavaScript Example

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FURTHER DATA

cpp.sh - C++ shell website
Scratchpad - Shift + F4 on Firefox - Javascript shell
Dev C++ - A free, portable, fast and simple C/C++ IDE
Code::Blocks - A free C, C++ and Fortran IDE
Ideone - an online compiler and debugging tool which allows youto compile source code and execute it online in more than 60 programming languages.

My Posts

Introduction From a Newbie Programmer.

Introduction to Computer Programming - part 1 (Lesson 1)

Introduction to Computer Programming - part 2 (Lesson 2)

Images from unsplash.com.

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