Computer Hardware: CPU and ALU

Main Computer Parts

• A computer is a machine that manipulates data based on a list of instructions, known as a program.
• A computer is an electronic device that accepts data as input, processes it, and provides information as output.
• The main components of a computer are hardware and software.

Hardware

• Hardware refers to the physical components that constitute a computer, including attached devices like input and output units, and secondary storage.
• Input units include devices like keyboards, mice, and scanners.

Central Processing Unit (CPU)

• The CPU is a component installed on the motherboard that serves as the computer's "electronic brain", and handles data processing.
• The CPU determines the computer type (e.g., P1, P2, P3).
• The CPU consists of the Arithmetic and Logic Unit (ALU) and the Control Unit.

Arithmetic and Logic Unit (ALU)

• The ALU executes calculations (addition, subtraction, multiplication, division) and logical processes (greater than, less than, equal to, etc.).

Control Unit

• The Control Unit supervises all computer units, directing work based on program instructions, and manages data access from input to main memory.
• It also handles data transfer between main memory and the ALU, and information flow from main memory to output and secondary storage.
• Registers, are temporary storage areas within the ALU and Control Unit, such as an Accumulator.
• Program counters, utilized in the control unit, store the address of the next command for execution.

Memory Unit

• Computer memory serves as a temporary storage area for data and instructions required by the CPU.
• Programs are loaded from storage before execution, enabling direct CPU access and needed for all computers.

Primary Memory

• Primary memory, or "main/internal memory," resides on the motherboard and is directly connected to the CPU.
• Primary memory stores small amounts of data, either from the manufacturer or the user.

RAM

• Some primary memory activities include: storing computer data in the input storage area, interim results in the working storage area, program orders in the program storage area, and final results in the output storage area.

• Also known as "random access memory," RAM temporarily stores data that is currently in use.

• RAM needs power to function, and loses its data when the computer is turned off, classing is as Volatile Memory.

• RAM is classified into two parts, SRAM and DRAM.

• SRAM (Static RAM)

  • SRAM retains its content as long as power is supplied.
  • SRAM does not need to be refreshed often.
  • SRAM is faster but more expensive than DRAM.

• DRAM (Dynamic RAM)

  • DRAM only holds data when electricity is available, needing periodic refreshing.
  • DRAM operates slower than SRAM.
  • DRAM is cheaper and needs less space.

ROM

• Also known as "Read-Only Memory," ROM primarily allows only reading of the stored data.
• Manufacturers usually store information in this memory, retaining the data even after the computer is off thus not being volatile.
• ROM contains the BIOS of the system.
• PROM (Programmable Read-Only Memory): Data can be stored once and cannot be altered therefore being unchangeable.
  • While initially written by the manufacturer, blank PROM chips can be programmed with special tools.
• EPROM (Erasable PROM): Data can be changed or erased through ultraviolet rays.
  • EPROM is much more expensive than PROM.
• EEPROM (Electrically Erasable PROM): It can be erased by electrical charges one byte at a time instead of erasing the entire chip with ultraviolet rays.

Secondary Memory

• Secondary Memory stores personal data in computer systems, allowing easy retrieval when needed and is a fundamental component of the computer system.
• Secondary memory is non-volatile, so data is retained when the power is off.
• Sequential Access: Data is searched sequentially or line by line until found (e.g., magnetic tape).
• Direct Access: The computer can directly access the user's intended information (e.g., magnetic disk, optical disk).

Magnetic Tape

• Magnetic tape resembles music cassette tapes and is used to store media like music and movies.
• It's not suited for storing data due to its sequential access that reads data line by line, thus lacking in accurate data location.

Magnetic Disk

• Magnetic Disks are a widely used storage medium for direct access secondary storage.

• Data saves automatically with the "save" button and do not lose data when there is a power loss because it is non-volatile.

• Operating Systems commonly store or install systems here, and include hard disks and floppy disks.

• Hard Disk (Hard Drive or Fixed Drive)

  • Hard disks house all files and data stored on the computer, and an average computer contains a 250GB-500GB hard drive.
  • For protection from virus risks, hard disks are divided into several parts, labeled with English letters (C:, D:, E:, etc.).

• Floppy Disk

  • These removable disks transfer data from one computer to another, being a round flat piece of Mylar plastic coated with a ferric oxide.
  • Floppy disks earlier came in 5 1/4" format and were then replaced by 3 1/2" disks due to lower storage capacity.
  • Now a days floppy disks are not used because of less storage and high rate.

Optical Disk

• It is a secondary storage medium that stores much more data, while constructed from a plastic disk coated with material.
• Optical disks are popular due to their small size and large storage capacity, and need an optical disk reader.
• The two types of optical disks are CDs and DVDs.
• CD (Compact Disk) stores data, music, movies, and software, with 80 minutes of continuous video and up to 700 MB of space - Data is stored in the form of "Pitts". - There are 2 types of CDs, CD ROM, and CD R/W.
• DVD (Digital Versatile Disk) is a high-capacity storage medium for movies, music, and software, storing up to 4.7 GB. - Requires a DVD drive in your computer, but it also also supports CDs. - There are 2 types of DVDs, DVD ROM, and DVD R/W.

Other Disks

• ZIP Disk: Similar to floppy disks but are larger in thickness and storage.
• Flash: Commonly called Flash Ram, it can transfer data between computers, with a storage capacity between 64MB to 32GB.

Output Units

• The most critical output is the monitor, where software appears as images and other outputs include printers, speakers, etc.

Software

• Software includes programs that are designed to perform a function, where the program is a sequence of instructions to solve a problem.
• The 2 types of software are system software and application software.

System Software

• The system software operates, controls, and extends the computer's own processing capabilities.

• These products are generally prepared by the computer manufacturers with low-level languages, to interact with the hardware.

• System software serves as the interface between the hardware and the end users.

• Common examples are Operating Systems, Utility, Compilers, and more.

• Operating System

  • The OS examples are:
  • DOS (Disk Operating System)
  • Windows (Windows 3.11, Windows 95, Windows NT, Windows 98, Windows me, Windows 2000, Windows XP, Windows 2003......etc.)
  • UNIX
  • LINUX

• Utility Programs:

  • Utility Programs are small systems programs doing specific and simple tasks, like copying a file or arranging data alphabetically or digitally.
  • Editor programs allow users to open files and write programs or data in the file.

• Compilers Programs:

  • These programs translate other programs, from computer languages like Basic, Pascal, and Fortran.
  • Translators will convert the programmer's 'source program' written into a machine language to an 'object program'.

Application Software

• Application software is designed to satisfy a specific need in an environment, like in a computer lab.
• Application software consists of a single program or a range of programs (also known as a software package), which accomplish tasks like spreadsheet packages.
• Common examples are Word Processing, Spreadsheets, Databases, Presentations, Graphics and Web Authoring.
• Features of application software include: being user friendly, high level language writing and simple to understand and use.

Programming Languages

• Any of multiple languages expressing a set of detailed instructions for a digital computer.
• They can be executed in machine language, after a simple substitution in a corresponding assembly language.

Machine Language

• Machine language, or machine/object code, comprises binary digits (bits) read and interpreted by the computer, is the only language computers can understand..
• The operating system dictates how a compiler writes a program to machine language.
• Debugging issues may occur due to the programmer's difficulty in detecting mistakes.
• To create computer programs, programming languages must be used, since the computer can not directly understand the language, and the program code must be compiled.

Assembly Language

• Expresses an order with specific symbols written in English, like "add".
• Differs from computer to computer, so a translated program (Assembler) is needed to convert to machine language.

High-Level Languages

• It is a programming language designed to simplify computer programming, and is multiple steps from the code on the processor.
• High-level source code has syntax read easily, and is converted later to low-level, that CPUs can work with.
• Examples are C++, C#, Cobol, Fortran, Java, JavaScript, Objective C, Pascal, Perl, PHP, Python, and Swift.
• The compilation converts the human readable-syntax of the high-level language into low-level code needed for a specific processor.

Starting Computer

• Start with the Start menu, desktop, and screen saver, move through the control panel, and learn about user accounts, themes, printers, mouse, folder options, sound, file structure, and windows updates.

• You can access programs and settings, by clicking the Windows start menu/icon, in the lower left corner of the screen.

• Below the left hand column is a search box that you can type a name, folder, program, or extension for the PC to locate.

• The shutdown button shuts down the computer properly.

• Other options can be found when you click the arrow on the shutdown button.

  • Switch users will leave the current user logged in and bring you back to the sign in where another user can log in.
  • Log off closes all programs and brings you back to the sign in menu.
  • Lock will require a password to be entered before being able to log back on.
  • Restart shuts down the computer then reboots.
  • Sleep will turn off the monitor and non-essential software.
  • Hibernate is for laptops and places open work on the hard drive and turning the computer off.