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Understanding the Command Line Interface: Essential Traits and Functions of Operating Systems

This guide explores the fundamental traits and functions of operating systems (OS) and their interaction with hardware. Learn how OS operates on specific processors, managing memory, executing commands, and providing essential interfaces for applications. Discover the significance of file types, naming conventions, and directory structures in managing data. This resource covers internal and external commands, as well as the necessary files for building a DOS environment. Perfect for beginners and those looking to deepen their understanding of OS operations.

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Understanding the Command Line Interface: Essential Traits and Functions of Operating Systems

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  1. Partial DOS Welcome to the Command Line Interface

  2. Operating System Traits • An OS only works with one type of processor • X86 processors for us; Motorola for Mac • Must understand the CPU’s abilities • How much memory it can use • What commands it understands and how to use them - You can write “High Level Code” and compile it for different processors

  3. Traits, cont. • OS starts running immediately after the POST test • Takes control of the computer from the POST test • Continues running until computer is rebooted or shut down • Can’t stop OS without stopping computer

  4. Traits, cont. • Application Programs can’t run without an OS • Word Processor, Spreadsheet, Web browser • Programmers write applications to run under a specific OS • We can compile application(s) for different OSs

  5. Functions of an OS • Must communicate with the hardware • Must create a User Interface • Must present available installed programs • Allow user to add, move and delete installed programs

  6. Organizing Programs and Data • To the computer, its all a file • The OS is one, or more, file(s) • Programs are file(s) • Data is stored in file(s) * Computer can only run three types of files: - .COM files (compiled) - .EXE files (also compiled) - .BAT files (text files)

  7. Types of Files OS files Application files Data Files Games ???

  8. Naming Drives • Use single letter only, followed by a colon • A: and B: reserved for floppy drive(s) • C: to Z: for hard disk, or other, drives • Maximum of 26 drives at any one time • Change drives (change focus) by typing drive letter (and colon) and press <Enter>

  9. Naming Files • 8.3 convention (DOS): • Up to eight characters for name • Up to three characters for file extension • Can’t use “special characters” – stick to letters and numbers and no spaces • My File is not valid • MyFile01 is valid file name • File names must be unique

  10. Directories • Directories can hold data or directories or both • Directory names are eight characters (or less) • Directory names do not have an extension (99.99% of the time – Word Perfect used extensions to baffle users)

  11. Organizing Files • Use directories and subdirectories; start with Root Directory (C:\) Root Directory C:\ Apps Data Stuff This is legal since fully qualified file name is: C:\Data\Jan\MyFile01 Jan Feb Mar MyFile01 MyFile01 File name here is: C:\Data\Feb\MyFile01

  12. Path • Fully Qualified Name is also the Path (to the file): • C:\Data\Jan\MyFile01 File Name Path

  13. Building DOS • Three main files and two optional files • IO.SYS which is basic device drivers • MSDOS.SYS more drivers and where optional files plug into the OS • COMMAND.COM which is the User Interface • IO.SYS and MSDOS.SYS are hidden files; COMMAND.COM is visible file in directory listing • Optional files are: CONFIG.SYS and AUTOEXEC.BAT – both are text files

  14. The Command Prompt Focus Directory (Root) C:\>_ Drive Letter Command Prompt (flashing)

  15. Internal and External • Internal commands are: • Found within COMMAND.COM much like chapters in the textbook • Can be run from any “location” on any drive • External commands are: • Programs in their own file • Have to be available to DOS via directory or path

  16. Internal Commands • DIR for directory listing • CD to change directory • MD to make a directory under the current directory • RD to remove a directory (has to be empty) • DEL to delete a file • COPY to copy a file from one location to another (and, optionally, to change name of file)

  17. External Commands • FDISK to partition a hard disk drive • FORMAT to format (prepare for data) a disk drive • SYS to copy system boot files to the location specified (has to be root directory)

  18. Boot Disk • Enough files (three for DOS) to load an operating system • Windows requires too many files to fit on a boot disk • Remember www.bootdisk.com – it might come in handy one day

  19. Virtual Disk • The boot disk that Windows 98 makes will build a virtual disk in RAM, unpack several files and report to you the drive letter assigned • This is a cute way to get ten pounds into a five-pound bag

  20. New Directories • When you make a (new) directory, DOS (and Windows) creates two files in that directory • One is DOT (.) which holds information about the new directory • The other is Double Dot (..) which holds information about the parent directory

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