Introduction to CPU Components and Operations

CPU Components

• The CPU is composed of two parts: the Control Unit and the Arithmetic Logic Unit (ALU).
• The Control Unit directs and controls other parts of the computer.
• The ALU executes arithmetic (+, -, ÷, x) and logical operations (AND, OR, XOR, NOT).

Registers

• Registers are temporary CPU storage areas for instructions, data, and addresses.
• Registers are faster than main memory.
• They are used to store, accept, and transfer data.

Bits and Bit Patterns

• A bit is a binary digit (either 0 or 1).
• Bit patterns represent information like numbers, text, images, and sound.

Boolean Operations

• Boolean operations manipulate one or more true/false values.
• Examples include AND, OR, XOR (exclusive OR), and NOT.

Gates

• Gates are devices that compute Boolean operations.
• They are often implemented as electronic circuits.
• They serve as building blocks for computers.
• VLSI (Very Large Scale Integration) involves using multiple gates on a single chip.

Memory Types

• Memory refers to the primary storage used for holding instructions and data being executed.
• It is also known as primary memory, main storage, internal storage, or RAM (Random Access Memory).
• Data in memory is typically lost when the computer is turned off.

Mass Storage

• Mass storage, also known as secondary storage, is used for storing data and programs for later use.

Magnetic Disk Storage

• Magnetic disk storage uses magnetized spots on a surface to represent data.
• Floppy disks were once used due to their portability and backup capabilities but are no longer common.
• Hard disks (HD) consist of rigid platters coated with magnetic oxide.
• Hard disks are known for their speed and capacity, with storage capacities reaching hundreds of gigabytes.
• Both removable and non-removable hard drives are available.

Hard Disk Organization

• Track is the circular portion of the disk surface that passes under the read/write head.
• Sector is a small arc on a track where information is recorded. Each sector typically holds 512 bytes of data.
• Zone recording allocates more sectors to outer tracks for more efficient storage use.
• Cluster is a fixed number of adjacent sectors treated as one unit of storage (typically 2-8 sectors).
• Cylinder consists of the same track number on all platters in a disk pack.

Hard Disk Access Speed

• Access time is the time it takes to read data from a hard disk.
• It comprises three components: seek time, head switching time, and rotational delay.
• Seek time is the time needed for the access arm to move over the desired track.
• Head switching refers to activating the specific read/write head for the targeted track and surface.
• Rotational delay is the time required for the desired data to rotate under the read/write head.

Magnetic Tape Storage

• Data is stored as magnetic spots on tape.
• Types include 3.5-inch reels, 3.5-inch cartridges, and cassette tapes.
• Tape storage capacity is measured in characters per inch (CPI) or bytes per inch (BPI).

Disk vs. Tape Storage

• Disks offer faster access and greater reliability but are more expensive.
• Tapes are mainly used for backups due to their lower cost.

Optical Disk Storage

• Data is represented by spots created using lasers on a metallic surface.

Compact Disks (CDs)

• CD-ROM drives can only read data from CDs.
• CD-R drives can write to a disk once.
• CD-RW drives can erase and rewrite data multiple times.

Digital Versatile Disk (DVD)

• Using a shorter wavelength laser, DVDs can store larger amounts of data than CDs.
• DVD drives can read both DVDs and CDs.
• DVDs are popular for storing full-length movies with improved sound quality compared to CDs.

Blue-ray Disks

• Blue-ray disks offer approximately five times more storage capacity than DVDs.

Flash Memory

• Flash memory is non-volatile RAM.
• Flash drives and Secure Digital (SD) Memory cards are popular examples.
• Advantages include reduced power consumption and smaller size compared to disk drives.

Files

• A file is a unit of data in mass storage systems.
• Fields are groups of characters within a file.
• Key fields are used to identify records.
• Physical record is a block of data conforming to the characteristics of a storage device.
• Logical record is a natural division of data within a file, which could be paragraphs or pages for text documents.

File Storage and Retrieval

• Buffer is a temporary storage area used during data transfers.
• Key identifies records uniquely.

Representing Information as Bit Patterns

• ASCII uses 7-bit patterns to represent text characters, primarily for English.
• Unicode utilizes 16-bit patterns for broader language support, covering languages like Chinese, Japanese, and Hebrew.

Representing Numeric Values

• Binary notation uses bits to represent numbers in base two.
• Overflow occurs when a value is too large for the computer to represent.
• Truncation happens when a value cannot be represented accurately.

Representing Images

• Bit map techniques utilize pixels (picture elements) to represent images.
• Each pixel is represented by one or more bits, depending on the image's complexity.
• RGB (Red, Green, Blue) color model uses three bytes per pixel to represent color intensity.
• Analytic geometry techniques, such as TrueType and PostScript, provide scalable image representations.

Representing Sound

• Sampling techniques record sound by capturing the amplitude of the sound wave periodically.
• The sample rate specifies the number of samples captured per second (e.g., 8000 samples per second).
• The captured numeric values are then transmitted to the receiving end.