2.1 Introduction of the computer:

A computer is an electronic machine that works with data by following instructions called programs. It can do calculations, make decisions, and handle input and output tasks by itself. Computers are used in many areas such as education, business, science, and entertainment.

The functional block diagram of a digital computer is shown in the diagram below. include mainly the input unit, the processing unit, the memory unit, and the output unit.

• The Input Unit is a part of the computer that is used to enter data and instructions. It takes data from the user and sends it to the computer for processing.
• The Processing Unit is the part of the computer that works on the data and instructions given by the user. It is also called the Central Processing Unit (CPU), and it is known as the “brain” of the computer.
• The Memory Unit is a part of the computer that stores data, instructions, and results. It helps the computer remember information while working and even after the work is done.
• The Output Unit is a part of the computer that shows the result after the computer finishes processing the data. It gives the final information to the user in a readable form. Example: Monitor, speaker, and printer.

2.2Input unit

• The Input Unit is a part of the computer that is used to enter data and instructions. It takes data from the user and sends it to the computer for processing.
• Some input devices are discussed below

KeyBoard:

A keyboard is an input device used to enter letters, numbers, and commands into a computer. It works like a typewriter but also includes special keys for performing different tasks. When you press a key, it sends a signal to the computer to type a character or perform an action.

Types of Keys on a Keyboard

Alpha keys: Alpha keys are the keys on a keyboard that include all the letters of the alphabet, from A to Z. They can be used in both uppercase (capital) and lowercase (small) letters, depending on the Shift key or Caps Lock key.Found in the main section of the keyboard.

Numerical keys: Numerical keys are the keys on a keyboard that include all the numbers from 0 to 9. it is used to type numbers and perform calculations.Found in two places on most keyboards Above the alphabet keys (top row) and On the numeric keypad (usually on the right side of the keyboard).

Function keys: Function keys are special keys on a keyboard labeled F1 to F12. They are usually found in a row at the top of the keyboard. Each function key has a special task or shortcut.

Control key: The Control key, often written as Ctrl, is a special key on the keyboard. It is used together with other keys to perform shortcuts or special commands.

Special keys: Special keys are keys on the keyboard that perform specific functions other than typing letters or numbers. They help control the computer or make typing easier.

Examples of Special Keys:

• Enter: Used to give a command or move to the next line.
• Backspace: Deletes the character before the cursor.
• Tab: Moves the cursor to the next space or field.
• Caps Lock: Turns typing letters into all capital letters.
• Shift: Used to type capital letters or special symbols.
• Esc (Escape): Cancels an operation or closes a window.
• Delete: Removes the character after the cursor.

Mouse:

A mouse is a pointing input device used to control the movement of the cursor on a computer screen. It helps users interact with the computer by clicking, selecting, dragging, and dropping items. It has mainly four parts: left, right buttons, scroll wheel, and sensor

Advantages of a Mouse:

1. • Simple and user-friendly for selecting and moving items.
   • Helps quickly move around the screen and open files or programs.
   •  Allows precise clicking and selection, useful in graphic design and games.
   •  Makes it easy to switch between windows, tabs, or tools.
   •  Useful for drawing, photo editing, and other creative tasks.

Scanner

A scanner is an input device that is used to copy pictures, documents, or text from paper into a computer. It works by scanning the image or document and converting it into a digital format that the computer can store, view, or edit.

Features of the scanner:

• Copies printed material into the computer.
• Converts physical documents into digital files like JPEG, PNG, or PDF.
• Helps save and share documents electronically.

Digital camera

A digital camera is an input device that captures photographs and videos in digital form. Instead of using film like old cameras, it stores images as digital files that can be viewed, edited, and shared on a computer or mobile device.

Main Features of the digital cemara:

• Captures images and videos electronically.
• Stores pictures in memory cards or internal storage.
• Allows users to transfer photos to a computer using USB, memory card, or wireless connection.
• Often includes features like zoom, flash, and display screen.

Arithmetic and logic unit and control unit:

• The Arithmetic Logic Unit (ALU) and Control Unit (CU) are essential components of a computer’s Central Processing Unit (CPU), working together to execute programs efficiently.
• The ALU is responsible for performing all mathematical operations, such as addition, subtraction, multiplication, and division, as well as logical operations like comparisons, bitwise operations (AND, OR, XOR, NOT), and data shifts.

• It processes data from registers or memory and returns the results for storage or further use.
• In contrast, the Control Unit acts as the CPU’s coordinator, managing the flow of instructions and data.

• It fetches instructions from memory, decodes them to understand the required actions, and sends control signals to the ALU, registers, and other components to execute those instructions in the correct sequence.
• Together, the ALU and CU enable the CPU to function as the computer’s “brain,” with the CU directing operations and the ALU handling computations. For instance, when a program executes an instruction like adding two numbers, the CU retrieves and decodes the instruction, while the ALU performs the actual addition. This coordinated effort ensures that programs run smoothly, processing data and managing system resources effectively.

2.4 Introduction to the Display Unit.

The major display unit in a computer, often referred to as a monitor or visual display unit (VDU), is an output device that presents visual information, such as text, images, videos, and graphical interfaces, generated by the computer’s central processing unit (CPU) and graphics processing unit (GPU). Below is a detailed explanation of the role and characteristics of the display unit in a computer system, complementing the earlier discussion of the Arithmetic Logic Unit (ALU) and Control Unit (CU).

Types of Display Units

Display units come in various forms, each utilizing different technologies to produce visuals. The most common types include:

1. Liquid Crystal Display (LCD):

   • Uses liquid crystals sandwiched between glass plates to control light and create images.
   • Common in modern monitors and laptops due to low power consumption, thin design, and sharp visuals.
   • Backlit by cold cathode fluorescent lamps (CCFL) or LEDs in newer models.

2. Light-Emitting Diode (LED):

   • A type of LCD that uses light-emitting diodes for backlighting, offering better contrast, energy efficiency, and thinner designs.
   • Variants include Organic LED (OLED), which uses organic compounds for vibrant colors and deep blacks, and Quantum Dot LED (QLED) for enhanced color accuracy.

3. Cathode Ray Tube (CRT):

   • Older technology using electron beams to excite phosphors on a screen to create images.
   • Bulky and power-intensive, largely replaced by LCD and LED displays but historically significant.

4. Plasma Displays:

   • Use ionized gas to illuminate pixels, offering good color reproduction and wide viewing angles.
   • Less common today due to high power consumption and cost.