Notes, summaries, assignments, exams, and problems for Computers

Database Management System (DBMS) Functions

A DBMS is a set of programs that provide access to data. Its primary functions include:

Core DBMS Capabilities

1. Facilitate Data Access: Enables easy access to data, including graphical representations.
2. Data Consistency and Integrity:
   • Consistency: Ensures any change respects the database integrity rules.
   • Integrity: Enforces restrictions (e.g., Laboral Age > 16).
   • Registration: Prevents duplicate entries (e.g., student not repeated).
   • Table Constraints: Limits on table size (e.g., N students per group < 35).
   • Relationships: Ensures referential integrity (e.g., a producer must have a valid vendor code existing in the suppliers table).
3. Database Security:
   • Making and retrieving Backups.
   • Reaction to system failures.

Audio editing is the process of manipulating and refining sound recordings. To understand this, it's essential to distinguish between analog and digital sound.

Analog vs. Digital Sound

Analog sound consists of continuous waves, while digital sound is represented by discrete values.

Analog Signals

Analog signals, which constitute analog sound, can take on all values of frequency and amplitude within a given range. They are continuous representations of sound waves.

Digital Signals

In contrast, digital signals, used for digital sound, take discrete values in both time and amplitude. For sound to be edited on a computer, it must first be digitized.

Digitizing Audio: Analog to Digital Conversion

The process of converting an analog signal into a digital... Continue reading "Digital Audio Fundamentals: Capture, Playback, and Processing" »

Model 802
IEEE defined in the 80s
Responsible for defining communication,
transmission, and use of LANs.

802.1: Definition Network International
We define that the network devices should be identified by 48 bits where the first 3 bytes are defined by the IEEE. This identifier must be unique for each product.

802.2: Logical Link Control (LLC)
It defines the controls for the transmission, i.e., defines handshaking.

802.3: Method of Access to the Medium
It defines the access method or wireless LAN, and collisions are resolved by the present CSMA/CA and CSMA/CD.

802.5: Token Ring
It defines the logical and physical topologies of Token Ring.

802.11: Wireless Networks (WiFi)
Establishes standards for speed, frequency, and scope in local wireless transmissions.... Continue reading "Understanding IEEE 802 Standards for Networking" »

Understanding MS-DOS CONFIG.SYS Configuration

The CONFIG.SYS file is crucial for configuring various system components, including MS-DOS, hardware, and applications, ensuring they function as intended.

System configuration information is primarily stored in the CONFIG.SYS file.

What is CONFIG.SYS?

It is a text file that contains special commands that configure computer components such as hardware (memory, keyboard, mouse, printer) for use by MS-DOS and applications.

It is the first file that runs when you start MS-DOS.

Location of CONFIG.SYS

It is usually located in the root directory, C:\.

CONFIG.SYS Runtime

MS-DOS executes this file each time you start your computer. However, if needed, you can instruct the system to skip it.

Why Modify CONFIG.SYS?

Repeaters

Repeaters: are network elements that regenerate the electrical signal that arrives in order to restore it to its original level, thus avoiding problems that might occur due to excessive attenuation. They operate at the physical layer of the OSI model, since they work with signals.

Hubs

A hub has the advantage of simply copying bits from other network segments. It requires no special configuration, being based on the physical layer. It serves no network addresses, protocols, services, etc. It simply repeats the signal from the network at high speed. It does not isolate the traffic problems generated by the network in each of the segments.

Bridges

Bridges: provide some capacity or element of control. They can accept and forward the frames... Continue reading "Understanding Repeaters, Hubs, Bridges, Switches, and VLANs" »

Data Link Protocols

LAPB, LAPF, and LAPD

These are Data Link protocols:

• LAPB (Link Access Procedure, Balanced): A subset of HDLC, providing asynchronous balanced mode (ABM) for point-to-point links between user systems and packet-switching network nodes.
• LAPF (Link Access Procedure for Frame-Mode Bearer Services): Includes a control protocol (similar to HDLC) and a core protocol (subset of the control protocol). LAPF control uses ABM and 7-bit sequence numbers. LAPF core has flag, address, information, and FCS fields, but no control field.
• LAPD (Link Access Procedure, D-Channel): Provides data link control over the ISDN D channel. Uses ABM, 7-bit sequence numbers, a 16-bit CRC FCS, and a two-part address field for device and logical user identification.

Oracle Tablespaces and Data Storage

System tablespaces and the required sysaux tablespace are created when the database is created and must be online.

The System tablespace is used for core functionality, for example, the data dictionary tables.

The auxiliary Sysaux tablespace is used for additional database components, such as the Enterprise Manager repository.

A tablespace accounts for one or more data files.

Data files belong to one tablespace.

User process: It begins when the user database server requests a connection to Oracle.

Process server: Connects to the Oracle instance and starts when a user establishes a session.

Background processes: Start the Oracle instance.

Oracle is a server management system database that provides an open, comprehensive,... Continue reading "Oracle Tablespaces, Segments, and Data Blocks Explained" »

Understanding Computer Memory

Memory Types

Main Memory

Main memory is integrated into the system's firmware and directly governed by the CPU. It stores the boot process, data from the stack, memory-resident programs, and the user program currently executing.

Types of Main Memory:

• Ferrite memories (obsolete)
• Integrated memory:
  • RAM (Random Access Memory)
  • ROM (Read-Only Memory)
  • PROM (Programmable ROM)
  • EPROM (Erasable Programmable ROM)
  • OTP Memory (One-Time Programmable ROM)
  • EAROM (Electrically Alterable ROM)

Cache Memory

Cache memory is located within the CPU and communicates directly with it. It stores frequently used data to reduce access time from main memory.

Mass Memory

Mass memory refers to storage devices with higher capacity, typically peripherals.

Types

Client-Server Model

• The client-server model defines the structure of communicating applications and their synchronization.
• It consists of two interacting processes:
  • Server Process
  • Client Process
• Client and server are inseparable; one cannot exist without the other.

Server

• This process awaits hearing on a given server port. It continuously waits for remote client processes to connect.
• Authentication
• Security and information privacy in the system where they reside.
• Must be able to handle requests from multiple clients simultaneously.
• Important: All clients will be connected to the same server port.

In general, we say that a computer is a server when its operating system runs one or more server processes (FTP, HTTP, DNS, etc.).

Client

• It is a process that sends

Video Capture and Storage

Factors Affecting Video Capture Speed

Which of the following is not a factor in the loss of speed in video capture to your computer?

• CD/DVD speed

Recommended Hard Disk Data Transfer Rate

For video capture, the recommended minimum hard disk data transfer rate is:

• 2.5 Mb/sec
• 5.0 Mb/sec
• 4.5 Mb/sec
• 3.5 Mb/sec

Peak Writing Definition

The amount of information a hard drive can write consistently in one second is called Peak Writing.

Data Compression

Compression Process

Compression is the process of removing or restoring data to reduce the size of a file.

Synchronous vs. Asynchronous Compression

When the algorithmic compression process takes the same amount of time as the decompression process, it is called Synchronous.

Audio Formats and