Computer Secondary Storage Devices

Secondary Storage Devices

• Programs and important data are stored in secondary storage devices.
• Disk drives are a common type of secondary storage device.
  • Data is stored magnetically on a circular disk.
  • Most computers have an internal disk drive.
  • Some have external disk drives, used for creating backup copies.
• Solid-State Drives (SSDs) are becoming increasingly popular.
  • They do not contain a disk and instead store data in solid-state memory.
  • They have no moving parts.
  • They operate faster than traditional disk drives.

Secondary Storage Devices (continued)

• USB drives are small devices that plug into a computer's Universal Serial Bus (USB) port.
  • They do not contain a disk.
  • Data is stored on flash memory.
  • They are also known as memory sticks and flash drives.
  • They are inexpensive, reliable, and small.
• Optical devices (CD or DVD) store data encoded as a series of pits on the disc's surface.
  • They use a laser to encode the data.
  • They hold large amounts of data.
  • They are a good medium for creating backups.

Cloud Storage

• Cloud storage allows users to store data on a remote server via the internet or a company's private network.
• Users can access their data from many different devices and from any location with a network connection.
• Cloud storage can also be used to backup important data stored on a computer's disk.

Input Devices

• Input devices collect data from people and other devices.
• Any data collected by a computer is called input.
• The hardware component that collects the data is called an input device.

Introduction to Computers and Programming

• People use computers in various settings, including school, work, and home.
• Devices that are considered computers include smartphones, iPods, tablets, and car navigation systems.
• Computers are designed to perform any task that their programs tell them to do.
• Programs are a set of instructions that a computer follows to perform a task.
• Programs are commonly referred to as software.

Programmers and Software Developers

• Programmers or software developers create computer software.
• They have the training and skill to design, create, and test computer programs.
• Computer programs are used in various fields, including business, education, and healthcare.

Hardware and Software

• The physical devices that a computer is made of are referred to as the computer's hardware.
• The programs that run on a computer are referred to as software.
• A computer is a system of devices that work together.

How Computers Store Data

• All data stored in a computer is converted to sequences of 0s and 1s.
• A computer's memory is divided into tiny storage locations known as bytes.
• One byte represents one number.
• A byte is divided into eight smaller storage locations known as bits (binary digits).
• Bits are tiny electrical components that can hold either a positive or negative charge.

Storing Numbers

• The positive charge or on position is represented by the digit 1.
• The negative charge or off position is represented by the digit 0.
• This corresponds to the binary numbering system, where all numeric values are written as a sequence of 0s and 1s.
• Each digit in a binary number has a value assigned to it.
• The largest value that can be stored in a byte with eight bits is 255.
• Two bytes are used for larger numbers, with a maximum value of 65535.

Storing Characters

• Characters are stored in a computer's memory as binary numbers.
• ASCII (American Standard Code for Information Interchange) is a coding scheme used to store characters.
• ASCII is a set of 128 numeric codes.
• Unicode is an extensive encoding scheme that is compatible with ASCII and represents characters for many languages in the world.

Advanced Number Storage

• The binary numbering system can only be used to represent integer numbers.
• Negative numbers are encoded using two's complement.
• Real numbers are encoded using floating-point notation.

Other Types of Data

• Digital data is stored in binary.
• A digital device is any device that works with binary data.
• Digital images are composed of tiny dots of color known as pixels (picture elements).
• Digital sound is broken into small pieces known as samples.

How a Program Works

• A computer's CPU can only understand instructions written in machine language.
• The fetch-decode-execute cycle is used to execute a program.
• The cycle consists of three steps: fetch, decode, and execute.

From Machine Language to Assembly Language

• Computers only understand machine language.
• Machine language is difficult to write.
• Assembly language uses short words known as mnemonics.
• An assembler is used to translate an assembly language program to machine language.

High-Level Languages

• Assembly language is referred to as a low-level language.
• High-level languages allow users to create powerful and complex programs without knowing how the CPU works.
• Examples of high-level languages include Java, C++, Python, Visual Basic, C#, Ada, and Fortran.

Key Words, Operators, and Syntax

• Key words or reserved words have specific meaning and purpose in a programming language.
• Operators perform various operations on data.
• Syntax is a set of rules that must be strictly followed when writing a program.
• Statements are individual instructions written in a programming language.

Compilers and Interpreters

• The statements written in a high-level language are called source code or simply code.
• Source code is translated to machine language using a compiler or an interpreter.
• Syntax error is a mistake, such as a misspelled word, missing punctuation character, or incorrect use of an operator.
• Compiler is a program that translates a high-level language program into a separate machine language program.
• An interpreter is a program that both translates and executes the instructions in a high-level language program.

Types of Software

• Programs generally fit into one of two categories: system software or application software.
• System software controls or enhances the operation of a computer.
• Application software makes a computer useful for everyday tasks.
• Examples of system software include operating systems, utility programs, and software development tools.
• Examples of application software include Microsoft Word, email programs, and web browsers.