# WHAT IS A COMPUTER?
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The word **Computer** is derived from the word **“Compute”**, which means **calculation and automation in the digital world**.
A **computer** is an **electronic device** that accepts data, processes it, stores it, and provides meaningful information to users. It performs operations accurately and follows the instructions given by the user.
A computer does not work emotionally; it works logically and provides exact results based on the data and commands received.
Thus, a computer can be defined as an electronic device with the ability to:
* Accept data and instructions from users
* Process the data into useful information
* Store data and instructions
* Perform arithmetic and logical operations
* Execute commands given by users accurately and efficiently
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# CHARACTERISTICS OF A COMPUTER
### 1. Accuracy
Computers perform calculations with a very high degree of accuracy and can solve complex calculations within seconds.
### 2. Speed
A computer is known for its high speed and can process millions of operations quickly.
### 3. Reliability
Computers are reliable devices that provide consistent and accurate results.
### 4. Versatility
Computers are used in different fields such as business, education, healthcare, communication, and technology.
### 5. Storage Capacity
Computers have a large storage capacity and can store huge amounts of data such as GB (Gigabytes) and TB (Terabytes).
### 6. Automation
Computers can execute programs automatically without continuous human intervention.
### 7. No IQ (No Intelligence of Their Own)
Computers are not intelligent by themselves. They only perform tasks according to user instructions.
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# WHAT IS CPU?
**CPU (Central Processing Unit)** is called the **brain of the computer**.
It performs:
* Calculations
* Data processing
* Arithmetic operations such as addition, subtraction, multiplication, and division
* Execution of instructions
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# WHAT IS ALU?
**ALU (Arithmetic Logic Unit)** is a part of the CPU.
It performs:
* Arithmetic operations (+, −, ×, ÷, %)
* Logical operations and comparisons
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# WHAT IS CONTROL UNIT (CU)?
The **Control Unit (CU)** controls and manages all operations inside the computer.
Functions:
* Controls data flow
* Coordinates between components
* Executes instructions step by step
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# WHAT ARE PERIPHERAL DEVICES?
Peripheral devices are external devices connected to a computer system.
Examples:
* Keyboard
* Mouse
* Monitor
* Printer
* Scanner
* Speakers
These devices help the computer receive input and provide output.
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# TYPES OF MEMORY
There are two main types of memory:
## 1. Primary Memory
Memory directly accessed by the CPU.
Example:
* RAM
## 2. Secondary Memory
Memory used for long-term storage.
Examples:
* Hard Disk
* SSD
* CD/DVD
### RAM (Random Access Memory)
* Primary memory
* High speed
* Temporary (Volatile)
### ROM (Read Only Memory)
* Permanent memory
* Stores important system instructions
* Data remains stored even after power off
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# HOW IS COMPUTER MEMORY MEASURED?
Computers work on the **Binary Number System**, which uses **0 and 1**.
## Bit
The smallest unit of data.
## Byte
1 Byte = 8 Bits
## Kilobyte (KB)
1 KB = 1024 Bytes
## Megabyte (MB)
1 MB = 1024 KB
## Gigabyte (GB)
1 GB = 1024 MB
## Terabyte (TB)
1 TB = 1024 GB
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# HARDWARE AND SOFTWARE
## Hardware
Hardware refers to the physical parts of a computer.
Examples:
* CPU
* Keyboard
* Mouse
* Monitor
* Printer
## Software
Software refers to programs and instructions that tell hardware what to do.
Examples:
* Operating System
* Browser
* Applications
* Games
* MS Word
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