Computer Systems: Hardware and Software

Introduction to Computer Systems

• This study guide covers computer components, software, operating systems, file systems, programming languages, and compilers.

Computer Definition and Functionality

• A computer processes information to produce a desired result.
• Computers process data through accepting input, processing input based on predefined rules (programs), and producing output.
• Computers are comprised of both software and hardware components.
• Computers function solely on given instructions, lacking intelligence or the ability to think independently.
• Solving problems through computers requires devising a method, breaking it into simple steps, and providing step-by-step instructions.
• A set of instructions for a computer to achieve a specific task is called a computer program (or software).
• Professional programs are called software, while the physical system is called hardware.

Hardware

• Hardware includes all physical components of a computer system that can be touched, such as the monitor, mouse, keyboard, hard disk drive, and system unit components like the motherboard, chips, and memory.
• A peripheral is a device like a disk drive, printer, modem or joystick connected to and controlled by a computer's microprocessor.

Hardware: Input Devices

• Input devices enter information into a computer, translating human-understandable data into computer-readable form.
• Input devices include touch screens, touchpads, scanners, microphones, pen inputs, trackballs, cameras, barcode readers, gamepads, electronic whiteboards, joysticks, and webcams.
• Standard keyboards have 104 keys, with the QWERTY layout being the most common.

Hardware: Output Devices

• Output devices, like printers, video displays, and speakers, present data from a computer to a user in human-readable form.
• Additional examples of output devices include monitors, plotters, projectors, computer output microfilm, LCD projection panels, headphones, and speech synthesizers.

Hardware: Input/Output (I/O) Devices

• Some hardware can provide data to a computer and receive data from it, depending on the situation.
• I/O devices include CD-R/RW, DVD, Blu-ray drives, digital cameras, fax machines, floppy diskette drives, hard drives, modems, NICs (network interface cards), SD Cards, sound cards, touch screens, and USB flash drives.

Computer System

• A "computer system" refers to a complete system that consists of all necessary modules or devices connected to the computer.
• A computer system combines three main hardware components: input devices, output devices, and the Central Processing Unit (CPU).
• The CPU, referred to as the computer, controls the system's operations by carrying out instructions in the operating system program and executing instructions when a program is run.

Central Processing Unit (CPU)

• The CPU consists of a processor and memory, with the processor containing control and arithmetic-logic units (ALU).
• The control unit fetches instructions from memory, decodes them, and directs the system to execute the indicated operations.
• The ALU performs arithmetic or logical operations using special registers and circuits.
• The memory unit, also known as internal, primary, main memory, or random access memory (RAM), stores instructions (programs) and data being executed, temporarily storing instructions and data for immediate use.

Program Execution

• CPUs are designed to perform simple operations on data, such as reading, adding, subtracting, multiplying, and dividing numbers.
• CPUs understand instructions written in machine language included in its instruction set, with each brand of CPU having its own instruction set.
• CPUs must perform multiple operations to carry out meaningful calculations.
• Programs are copied from secondary memory to RAM each time the CPU executes them.
• The CPU executes programs in cycles: fetching the next instruction from memory, decoding the fetched instruction to determine the operation, and executing the operation.

Primary Memory: RAM

• RAM is a type of memory accessed directly by the processor, also referred to as main or internal memory, and is largely classified into two types.
• Random Access Memory (RAM) is used for immediate tasks on a temporary basis and is volatile, meaning stored data is erased after usage.
• Dynamic RAM requires constant refreshing, typically in milliseconds, to retain data.
• Static RAM does not erase data as long as the system remains powered on but data is erased when shut down.

Primary Memory: ROM

• Read-Only Memory (ROM) is a permanent storage form containing data that is read-only and cannot be edited.
• The data stored in ROM is used to boot the system.
• Types of ROM include Masked ROM, Programmable ROM, Erasable and Programmable ROM, and Electrically Erasable and Programmable ROM.

Memory Types

• Volatile Memory: Loses its data when power is shut off; RAM and cache memory are examples.
• Non-Volatile Memory: Retains data when power is removed; ROM is one example.

Memory Storage

• Secondary storage can hold data for extended periods.
• Programs are normally stored in secondary and loaded to main memory when needed.
• Types of secondary memory:
  • Disk drive: magnetically encodes data onto a spinning circular disk
  • Solid state drive: faster than disk drive, no moving parts, stores data in solid state memory
  • Flash memory: portable, no physical disk
  • Optical devices: data encoded optically

Unit of Measurement

• The basic unit of measurement for computer data is the binary digit, or bit.
• A bit is the smallest unit of information, expressed as 1s or 0s; all files and communications use the binary number system.
  • Byte = 8 bits
  • Kilobyte (KB) = 1024 bytes
  • Megabyte (MB) = 1024 Kilobytes
  • Gigabyte (GB) = 1024 Megabytes
  • Terabyte (TB) = 1024 Gigabytes

Computer Speed

• Processing unit speed is measured in Hertz (Hz) relative to the CPU cycle.
  • 1 Hz = 1 cycle per second
  • 1 Megahertz (MHz) = 1 million cycles per second
  • 1 Gigahertz (GHz) = 1 billion cycles per second

Software

• Software is a generic term for organized collections of computer data and instructions.
• System software provides basic non-task-specific computer functions.
• Application software is used by users to accomplish specific tasks.

System Software

• System software manages the computer system, controlling all hardware components.
• It integrates and manages hardware, presenting a functional unit to other software and users without needing to know the low-level details.
• System software includes the operating system, disk formatters, file managers, display managers, text editors, user authentication and management tools, networking, and device control software.
• Operating systems include Linux, Unix, Microsoft Windows, MAC OS, MS-DOS, Ubuntu, Haiku, Android OS, Blackberry OS, and Debian.

Operating System

• The operating system is a program that controls the overall operation of the computer and must be provided before any other program or data.
• Booting/bootstrapping is the process of copying the operating system program from the system disk or hard disk into memory.
• An operating system has three primary functions:
  • Coordinates and manipulates computer hardware.
  • Organizes files on various storage media.
  • Manages hardware errors and data loss.
• Common OS include window 98, Windows NT, MAC OS, and UNIX

Application Software

• Application software performs specific tasks beyond running the computer system.
• It can be a single program, a small collection of programs (software package), or a larger collection (software suite).
• Examples include a a larger collection (software suite) of related but independent programs and packages that have a common user interface or shared data format, such as Microsoft Office, which consists of closely integrated word processor, spreadsheet, database, and database management systems
• Application software is built to perform specific tasks rather than controlling the system like system software.
• Examples include web browsers (Google Chrome, Safari, Opera, Mozilla Firefox), word processors (Microsoft Office, Google Docs, LibreOffice, AppleWorks), calculator software, GPS, and database software (MySQL, WhatsApp Web).

Machine Code/Language

• In machine languages, instructions are written as sequences of 1s and 0s, called bits, that computers directly understand.
• All executable programs are read by the computer in machine language, but they are not always programmed in it.
• Programming directly in machine language is difficult due to instructions being sequences of 1s and 0s.

Programming Languages

• Programming languages are artificial languages that define instruction sequences that computers can process and execute.
• Translation from source code to machine code needs to be automated using a program, such as a compiler.
• Computers cannot understand natural languages like English due to ambiguities.

Compilers

• Asking the computer to carry out instructions in a program is "executing the program" or "running" it.
• Only programs in machine language can be executed, so computer scientists developed compilers to translate programs from other languages into machine language.
• Compilers translate text written in a computer language (source language) into another computer language (target language).
• The original sequence is called source code, and the output is called object code.
• A compiler primarily translates source code from a high-level to a low-level language, which could be machine language.

Low-Level Language

• A low-level language has little to no abstraction from the computer's microprocessor.
• Low-level does not imply that the language is inferior to high-level programming languages but rather refers to the small or nonexistent amount of abstraction between language and machine language
• Low-level languages are close to the "hardware".

High-Level Language

• High-level languages are more abstract and easier to use compared to low-level languages.
• High-level languages use English-like keywords and translate into multiple machine-language instructions. Examples include Pascal, Visual Basic, C++, and Java.