Introduction to Computer Science

Computer Science Overview

• Computer science involves studying the theory, experimentation, and engineering behind computer design and utilization.
• Computer science delves into the theoretical underpinnings of information and computation.
• The field also covers practical techniques for their implementation and application in computer systems.
• Computer science utilizes a scientific and practical approach, systematically studying computation, its applications, the feasibility, structure, and mechanization of algorithms.
• Algorithms are methodological procedures underlying the acquisition, representation, processing, storage, communication, and access to information.
• Computer graphics emphasize real-world visual applications.
• Programming language theory explores different approaches to describing computation.
• The study of computer programming examines various aspects of programming language use and complex systems.
• Human-computer interaction focuses on making computers and computations useful, usable & universally accessible.
• Computer Science branches into engineering, communication, and other fields like AI and NLP.
• The engineering branch includes computer, software, and hardware engineering.
• The communication branch includes basic and mobile networking, and distributed systems.
• Other computer science fields are artificial intelligence, NLP, GIS, remote sensing, and pervasive computing.

Computer Definition

• A computer is an electronic device taking input such as raw data like numbers, text, sound, images, animations, or video.
• It processes the data and presents meaningful information as output.

Data & Information

• Data is raw, unorganized facts that require processing.
• Data can be a collection of symbols representing a thing, a concept, or an event.
• Data is any collection of figures arranged by a general principle or convention.
• Data processing is rearranging collected data to desire it more useful, involves collecting, arranging, and representing facts with rules.
• Information is processed, organized, structured, or presented data in a specific context to provide utility.
• When input is information, the process is called information processing.

Computer Systems Evolution

• Early computer systems had multiple users per computer.
• Current computer systems have one primary user per computer and multiple computers per user.

Computer Generations

• Computer generations are categorized by technological advancements, though specific dates are not definitively agreed upon.
• The four generations are distinguished by electronic circuit elements used, storage media, computer language, OS type, and memory access time.
• Computer generations are categorized by hardware improvements, typically with tenfold or better increases in speed and reliability.

First Generation (1950s)

• Vacuum tubes were used as key electronic components.
• Input was mainly via punched cards, with magnetic drums for internal storage.
• Operated at millisecond speeds, handling over 10,000 additions per second.
• Used primarily for scientific calculations.

Second Generation (Early 1960s)

• Transistors replaced vacuum tubes as the main circuit component.
• Transistors were smaller, faster, and more reliable than vacuum tubes.
• Magnetic cores were used for main storage.
• Speed improved to microseconds, allowing over 200,000 additions per second.
• Business applications became more common with large data files stored on magnetic tape and disk.
• Examples: IBM 1620 (scientific), IBM 1401 (small to medium commercial), and IBM 7094 (large scientific).
• COBOL and FORTRAN high-level languages were introduced.
• Batch operating systems facilitated rapid magnetic tape file processing.

Third Generation (Late 1960s, Early 1970s)

• Characterized by solid-state logic and integrated circuits (ICs).
• Computer storage shifted from magnetic cores to integrated circuit boards for modularity and compatibility.
• Software importance grew, using sophisticated OS, and improved programming languages.
• Optical scanning and plotters were new input/output methods.
• Example systems include the IBM System/360 and IBM 1130.

Fourth Generation (Late 1970s, Early 1980s)

• Marked by greatly expanded storage and improved circuitry.
• Utilized large-scale integrated circuits (LSI) with hundreds of thousands of transistors on a silicon chip.
• Computer memory operated at nanosecond speeds; large computers could add 15 million numbers per second.

Fifth Generation

• Architecture is still in progress which adapts to technological changes.
• A simple and natural methodology for solving problems is being sought.
• Uses intelligent processors that can draw inferences.
• Users will also be able to interact with them in natural languages such as English, and German.

Computer Classification

• Computers are classified based on method of processing, application, and physical attributes.

Classification by Processing Method

Analog Computers

• Operate by measuring continuous variables like pressure, temperature, voltage, and current.
• Analog computers are designed for special purposes.
• Examples include thermometers, voltmeters, speedometers, and gasoline pumps.

Digital Computers

• Operate by counting discrete variables.
• They operate on numbers/digits representing numbers, letters, or symbols.
• Digital computers offer higher accuracy and speed than analog ones.
• Examples include abaci, desk computers, pocket computers, and most general-purpose machines.

Hybrid Computers

• Combine the best features of analog and digital computers.
• Hybrid computers process information by collecting input data via analog methods, converting it to digital quantities.
• The digital values are processed and output from digital to analog.
• For example, ICU analog devices measure vital signs, convert them to digital for monitoring, and alert nurses to abnormalities.

Classification by Application

Special Purpose Computers

• Designed to solve a single type of problem with specific components and uniquely adapted functions.
• Most analog computers are special purpose computers.
• Other examples are public telephone boxes, traffic control systems, and ticket machines.

General Purpose Computers

• Designed to solve a variety of problems using a "stored program concept".
• To solve A set of instructions for a specific problem is read and stored in memory executed step by step.
• The same computer can be applied to solve a variety of problems.
• General computers are more flexible and versatile such as micro, mini, and supercomputers.

Classification by Physical Size

• General-purpose digital computers are classified by capacity and size.

Supercomputers

• The fastest, largest, and most powerful type of computer with operation speeds in hundreds of millions per second.
• Supercomputers have an 80 million character primary memory and a 20 times larger secondary memory.
• Multi-user systems in intercontinental range can conduct complex scientific calculations.
• Used in space technology centers, meteorology stations, astronomical observatories, intercontinental communications, and airline organizations.

Mainframe Computers

• Smaller than supercomputers in size and capacity, as well as lower in speed & memory.
• Multi-user systems handle hundreds of users.
• Older mainframes used punched cards for data input.
• Used predominantly in large organizations.

Minicomputers

• Have relatively lower speed, can handle multi-users, are smaller than mainframes.
• They use terminals for inputs and output.
• Used in smaller organizations.

Microcomputers

• The most widely used type of computer.
• Single-user systems which fit on desktops, and are of varying capacity and easy to handle.
• Sometimes referred to as personal computers.
• A video display unit is used for output.
• Data is entered through the keyboard and by the help of floppy disk.

Computer Systems

• A system includes components, subsystems, or procedures working together to achieve an objective.
• The basic units of a computer system include CPU, Storage Devices, Input Devices, Output Devices and Communication Bus.

Hardware

• Physical equipment of the computer system.

Software

• Is the collection of programs, routines, documentations, rules and operational procedures which tell the computer what to do.

Central Processing Unit (CPU) or Processor

• Referred to as the brain of the system.
• Contains electronic circuits for data processing.
• Performs operations based on instructions from input devices.
• Controls data flow, system entry, memory placement/retrieval, and output direction.
• The CPU contains the Arithmetical Logic Unit and Control Unit.
• ALU (Arithmetical Logic Unit): Takes logical decisions and performs arithmetical calculations.
• CU (Control unit): Controls activities of other units; it receives instructions from memory, decodes them, and decides on routing and storage.

Memory

RAM (Random Access Memory)

• Memory directly accessible by the control unit and ALU.
• Memory locations are accessed directly.
• Memory locations are accessed using address.
• Holds instructions and data elements.
• Data is lost with power is off.

ROM (Read Only Memory)

• Integrated into the computer's circuitry; cannot be altered without altering the circuitry.
• Used to store basic hardware information.

Secondary Storage

• Secondary/auxiliary storage includes media like punched cards, paper tape, magnetic tape, magnetic disk, and magnetic drum.
• Storage media stores data and information permanently.
• Magnetic tapes can be used for data storage.
• Data density and convenience make magnetic tapes a popular secondary storage medium.
• The data is stored on Mylar plastic which is magnetized by a read/write head in either a seven-track or nine-track format.
• Magnetic disks contain metal or plastic platters coated in ferrous oxide for magnetizing data.
• Magnetic disks allow random access to information.
• Example: HDD

Hard Disk Drive (HDD)

• Reads/writes data on disk.
• Is a high-capacity disk made of fixed metal.
• Serves as secondary storage which enables fast accessibility of data.
• Disks are grouped into a disk pack, separated by air spaces for read/write head access.
• Each disk has approximately 200 tracks where information is stored.
• Tracks share the same number.
• Rotates the disk pack at speeds reaching 1,000 revolutions per second.
• The set of tracks available on one movement of the access mechanism is known as a cylinder.
• Disk access time refers to retrieve (or store) data from (or to) disk.

Compact Disk Read Only Memory (CD ROM)

• Thin polycarbonate plastic with a metal layer and lacquer.
• It measures 120mm in diameter.
• Used in multimedia for transferring data from one place to another to secure it.
• It can be used for music and software storage. - It's read-only; manufacture can only put data on them.

Input/Output Devices

Input devices

• This unit enters data into the computer.
• Converts information from a human-understandable form to a computer-understandable one.
• Examples: keyboard, mouse, scanner, light pen, voice synthesizer, CD-ROM drive, etc.

Output Devices

• Obtains data from the computer for examination, analysis, and external distribution.
• Converts results from a machine-understandable form to a human-understandable form.
• Examples include Visual Display Units (VDU), printers, plotters, voice response units, and disk drives.

Communication Bus

• An electronic circuit, which produces a communication path between the computer system components to transfer data.
• Internal Bus bus communicates the CPU, while the External Bus communicates the CPU with memory and peripherals determining computer efficiency.

Computer Software

• Computer hardware is an electronic device which performs a task to solve a problem.
• Precise instructions need to be provided for the hardware to solve the problem .
• A finite set of instructions a computer follows to perform a given job is a program.
• The program is first loaded into memory to be executed in the memory.
• Software is a collection of programs and routines supporting tasks on a computer, including documentation, rules, and procedures.
• Acts as an interface between the user and the electronic components of the computer.
• Computer software is classified into system software and application software.

System Software

• Programs facilitating the work of computer hardware that manage machine resources, and input/output devices.
• Controls hardware performing functions the user cannot or should not handle, makes complex hardware more user-friendly.
• It acts as an intermediary between the user and the hardware.
• It translates programming languages for the computer, serving as communication between the user and computer.

Operating system (OS)

• Coordinates the activity between the user and the computer and serves as an intermediary between programs and hardware.
• Operating system types are classified by the number of programs it can handle at a time.
• and the number of user's it can serve at once at one or different stations

Single-user, Single tasking operating systems

• Runs only one program at a time.
• An existing program must be removed before loading another.

Single-user, multi-tasking operating systems

• Allows a user to run several programs simultaneously.
• Used on desktop and laptop computers today such as Windows, iOS.
• For instance, a Windows can write a document, while downloading a large file from the internet simultaneously.

Multi-user Operating System

• Allows multiple users to take advantage of the computer’s resources simultaneously.
• Needs manage resources and prioritize users so that one may not affect the other.
• Unix and VMX, which are examples of MVS (Multiple Virtual Storage), manage users well.
• Differs from single-user OS with networking capabilities.

Real Time Operating System (RTOS)

• A capable of processing data quickly.
• Used in machinery, scientific instruments, and industrial systems.
• Manages resources effectively, executing operations in consistent timeframes to maintain system stability.

Language Software

• Language software is used to develop application software.
• Also translates programs to machine code.
• Consists of editors and translators.
• A translator converts one or more languages to another language.
• Assemblers, compilers, and interpreters are the three types of translator.

Assembler

• Translates assembly languages into machine code.
• Takes basic computer instructions and converts them into a pattern of bits that the computer’s processor can then use.
• Programmers can write code with assembler instructions whose sequence is known as source code/program.
• The assembler program takes each statement inside a source program and generates a corresponding bit pattern/stream.
• The assembler program output is called either object code or object program.
• Sequence of 0’s and 1’s are sometimes called machine code.
• The object program can then be run desired.

Compiler

• Translates a source program into machine readable code.
• Computer software that translates computer code from one programming language to another

Interpreter

• Translates each instruction of high-level language and executes it before translating the next instruction.
• There are two ways to translate programs written in a high-level language.
• Either to compile or translate via an Interpreter in the most popular method.
• PHP is one of the most common languages that uses the interpreter function.

High-level programming languages Vs Low-level programming languages

• High-level languages simplify computer programming; contain easy-to-read.
• After they syntax, they are converted to low-level, before being recognized by A CPU.
• Examples include: C++, C#, Java, JavaScript, PHP, Python.
• Low-level languages work closer with a computer’s hardware, manage computer semantics, and handle hardware architecture.
• Machine language and assembly language are common.

Procedural vs Structured vs Object-Oriented Programming Languages

• Procedural consists of calls and code. Example Basic
• Structured emphasizes program data from its function. Example C
• Object orientated focuses on objects. Example Java.

Application Software

• Software designed to perform specific tasks, also called application packages.

Malwares

• Computer programs that interfere with computer hardware and operating system with unique traits & characteristics.

Virus Programs

• Malicious program spreads by infecting others.

Worm Virus

• Self-replicates without a program.

Trojan horse

• It is a malicious program disguised as a legitimate program.

Spyware

• Designed to collect data on computer users.

Ransomware

• Infects/ encrypts a system with a ransom for payment. All malware replicates other files by altering them.