# What Makes a Computer a Computer?

Throughout history, humans have built tools to help them solve problems. Computers were originally built to help humans with the thinking we do, such as solving equations and tracking stars in the sky.

Computers were designed to manipulate information needed to perform 4 different tasks. All computers have these same 4 tasks:

1. Take input
2. Store information
3. Process information
4. Output the results

## Binary and Data

Wires and circuits carry all the information inside a computer.

### Binary Number System

The Binary Number System is executed using only two digits: 0 and 1

Any number can be represented with the Binary Number System by multiplying each integer in increments of two (starting with the last integer) and adding the results together.

For example: 1001 = 9

(1 x 8) + (0 x 4) + (0 x 2) + (1 x 1)

Text, images, graphics, sound, photos and videos can all be represented by the Binary Number System.

### Text

Each individual letter is identified by a number 1-26 according to location in the American Alphabet. From there, the number is converted into binary. Each word and paragraph follow the same system.

### Photos, Videos and Graphics

These images are broken down into pixels. Each pixel is made up of colors. The colors displayed are made possible by the Binary Number System. A single photo is made of millions of pixels.

### Sound

The waveform is created using the Binary Number System. The more bits a sound file has, the higher range it will have.

## Circuits and Logic

### Simple Circuit

A simple circuit takes an electric signal and flips it.

For example:

• 1 changes to 0
• 0 changes to 1

### Complicated Circuit

A complicated circuit takes multiple signals & combines them to give different results.

### Logic Gates

By connecting different circuits together, we can make more complex circuits that perform more complex calculations.

This circuit takes in 2 bit and adds them together to calculate the sum. To add larger numbers, put two circuits side-by-side. Different electrical currents can perform other calculations, like substraction and multiplication.

### Modern Computers

Why are smaller computers faster? Electricity travels a shorter distance in a smaller circuit. Electricity moves at just about the speed of light. A smaller computer means the electricity has a shorter distance to travel. Modern circuits can perform billions of calculations per second.

## CPU, Memory, Input and Output

The Central Processing Unit, known as the CPU, calculates information. This is the masterchip that controls the other parts of the computer. The CPU knows which circuits to use and when to use them. Here is the process:

• The keybord converts a letter into a number
• Numbers are sent as binary into the computer
• The CPU calculates how to display pixel-by-pixel
• Memory tells it how to draw (The CPU runs these instructions and stores it as pixels in the memory)
• Pixel information is sent as binary to the screen
• The screen converts the binary information into pixels that make up what you see

## Hardware and Software

### Hardware

The circuits, chips, wires, speakers plugs and other elements located inside the computer make up the hardware.

### Software

The code running on the machine is known as software, like Python, Ruby and Blockly. This type of code is written in a format that resembles stanard English before it is sent to the CPU. Now the CPU changes the code into binary and sends it to the display.

## Vocabulary

• Bit: smallest piece of info
• Adder: this circuit takes in 2 bit and adds them together to calculate the sum
• CPU: Central Processing Unit
• Hardware: physical elements inside the machine
• Software: code running on the machine
• Operating system: the master program that manages how software uses the hardware of a computer