System Software and Operating Systems

1. System Software and Operating Systems Chapter 3 in Computing Essentials 2000-2001 (O’Leary and O’Leary)

2. Hardware consists of the parts of the computer you can touch keyboard, mouse, monitor, printer, drives, motherboard, CPU and so on Software is simply a set of instructions (a.k.a. a program), it tells the hardware what to do and when to do it Hardware vs. Software

3. While the software (the instructions) are stored on chips or disks, it is distinct from them Analogy: in the same way that a musical score is distinct from the paper it’s printed on or the CD recording of it Hardware is the part of the computer you can kick; if you can only curse at it it’s software Software within Hardware

4. An “interface” is a boundary or region of contact between two entities and typically where any interaction or exchange takes place The interface between the user and hardware is multi-layered There are interfaces within interfaces Interface

5. The layer closest to the user consists of “application packages” (like Word, Excel and PowerPoint) that help the user perform particular tasks and high-level languages (like C, Basic, Pascal, Fortran, etc.) the layer closest to the software is called the BIOS (Basic Input/Output System) In between lies the “operating system” The various levels

6. The BIOS is a set of instructions stored on a read-only memory (ROM) chip It is sometimes called “firmware” since it occupies the middle ground between software and hardware. (The instructions are built right into the chip.) You may see the term BIOS on the screen soon after you turn on the power BIOS

7. It checks on (detects) the other parts: memory, keyboard, mouse and so on Then it looks for the “boot program” that will load the operating system It always looks to the floppy disk drive first, which is why you shouldn’t have a floppy in the drive when you are booting the system BIOS (cont.)

8. While it is most noticeable during the boot process, the BIOS is used constantly This separation of BIOS from operating system allows for changes in hardware without a major rewriting of the operating system software BIOS (cont.)

9. If one has a new piece of hardware, the interface instructions connecting it and the operating system may not be written into the system’s ROM chip, the software (as opposed to firmware) is needed This software is called a “device driver” Device Drivers

10. Between the high-level (user friendly) applications and the BIOS is the “system software,” most notably the operating system but also language translators and utilities The operating system consists of programs for loading and executing applications, storing or retrieving files, managing the CPU, switching between tasks and so on The Vast In-Between

11. File Viewer: shows you the file or part thereof, esp. if it’s a graphic file File Conversion: takes in one format and turns it into a another File Compression: shrinks the size of stored files Backup: makes a copy of your files in case of a system crash Utilities

12. Diagnostics: are things installed and working properly? Uninstaller: gets rid of applications you no longer want Anti-virus: seek and destroy virus, protection too Screen Saver: it used to be that it literally saved the screen, now mostly entertainment, sometimes security Utilities (Cont.)

13. Desktop Enhancer: organizes desktop Internet manager: manage your website LANGUAGE TRANSLATOR: takes a programmer’s high-level code and converts it to a binary code that computer components “understand.” (Again this is done in several stages.) Utilities and Language Translator

14. Command-line interface: the user types keywords (commands) after a prompt Menu-driven interface: the user selects options from a menu typically using the arrow and Enter keys Graphical User Interface (GUI): the user points to icons with the mouse, etc. Op. Sys. Types of Interfaces

15. Especially with GUI interfaces, operating systems have become rather large Once the boot program is loaded into memory, it in turn loads the essential parts and the more frequently used commands (the kernel) of the operating system The rest (the external commands) are loaded only when needed The kernel

16. Operating systems may be distinguished in whether they allow multi-tasking multi-threading multi-users multi-processors Multi-this, Multi-that

17. A task or process is a program or part of a program the user wants executed Modern operating systems are multi-tasking in that they execute two or more applications running simultaneously (actually they switch back and forth between the applications) Older single-tasking operating systems could only do one thing at a time Multi-tasking

18. context switching: only one process is active, but the status of the other process is preserved cooperative multitasking: switching occurs at natural breaks in the process, but one application can take over preemptive multi-tasking: tasks are prioritized and looked in on often so that one of them does not monopolize the CPU Types of multi-tasking

19. Multi-threading: similar to multi-tasking but takes place within a single application, e.g. one wants to take in typed information and see it on the screen simultaneously Multi-user: having more than one user, operating systems for work stations, mainframe, mini and supercomputers allow for more than one user Multi-threading and Multi-user

20. If a single CPU is insufficient for your computing purposes, you may need an operating system which can coordinate a number of CPU’s (processors) asymmetric: different tasks assigned to different CPU’s each with its own memory symmetric: tasks and memory shared equally among CPU’s Multi-processor

21. The operating system manages the processes manages the memory temporary storage (e.g. buffers) more permanent (e.g. disks) manages input and output manages security monitors performance System Management

22. An important distinction in the business life of an operating system Proprietary: limited to a specific vendor or computer model, marries software to specific company’s hardware Portable: will run on many different systems one can change hardware companies without changing software companies Proprietary vs. Portable

23. MS-DOS (Microsoft Disk Operating System) Windows 3.0 and 3.1 Windows 95 Windows 98 Windows NT Windows 2000 Some Operating Systems

24. Macintosh OS/2 UNIX NetWare Some more OP’s