System Software

Chapter 06 System Software

As for today, we learned about the system software and explored the popular OSs.

First of all, let's discuss about the system software.

System Software includes all of the programs needed to keep a computer and its peripheral devices running smoothly. There are two major categories of system software, which are the operating systems (OS) and the system utilities.

The operating system (OS) is a set of programs that perform certain basic functions with a specific type of hardware. The functions of the operating system are:

• Starting the computer

Booting is the process of loading or reloading the operating system into the computer’s memory. The booting processes are:

1. Cold boot – Loads the OS when the power is turned on
2. Warm boot – Reloads the OS when the computer is already on (Sleep Mode)

The computer copies the kernel from the hard drive into the computer’s memory. The kernel:

• Is the central part of the operating system
• Starts all applications
• Manages devices and memory
• Resides in memory at all times
• Performs other essential functions

The step-by-step booting process:

Step 1: The BIOS and Setup Program


• BIOS (basic input/output system) is the part of the system software that includes the instructions that the computer uses to accept input and output
• Setup program is a special program containing settings that control the computer’s hardware. The program can be accessed while the BIOS information is visible.

Step 2: The Power-On-Self-Test (POST)


• POST (power-on-self-test) is a series of tests conducted on the computer’s main memory (random access memory or RAM), input/output devices, disk drives, and the hard disk.
• BIOS conducts a Power-On-Self-Test (POST) to check the input/output system for operability.
• The computer will produce a beeping sound and an error message will appear on the monitor if any problems are encountered.

Step 3: The Operating System (OS) Loads


• BIOS searches for the OS.
• Settings in the complementary metal-oxide semiconductor (CMOS) determine where to look for the OS.
• The operating system’s kernel is loaded into the computer’s memory.
• The OS takes control of the computer and begins loading system configuration information.

Step 4: System Configuration

• Registry is a database that stores information about peripherals (computer equipments) and software.
• Driver utility program that makes peripheral devices function properly
• The system is configured from the operating system’s registry.
• Drivers are loaded into memory.

Step 5: System Utilities Loads

• System utilities are loaded into memory.
• Volume control
• Antivirus software

Step 6: User Authentication

• Authentication or user login occurs. The computer asks for user's name and the password.
• The user interface starts, enabling user interaction with computer programs.

That's all about starting the computer. Next Operating System's function is,

• Managing Applications

Single-tasking OSs run one application program at a time. While multitasking OSs have the ability to run more than one application program at a time. Multitasking is accomplished by:

• A foreground application is the active program or program in use
• A background applications is the inactive program or program not in use.

Preemptive multitasking enables the OS to regain control if an application stops working.

Another Operating System's function is,

• Managing Memory

Basically, computers use memory to make processing more fluid. The operating system allocates memory areas for each running program; it keeps programs from interfering with each other. The operating system also uses virtual memory (part of hard disk) as an extension of random access memory (RAM) and of course it's slower than RAM.

Next Operating System's function is,

• Handling Input and Output

Input and output devices generate interrupts, or signals, that tell the operating system that something has happened.

The OS provides interrupt handlers or mini-programs that begin when an interrupt occurs.
Interrupt request (IRQ) lines handle the communications between input/output devices and the CPU.

An IRQ conflict causes system instability when two devices try to use the same IRQ line.

The last Operating System's function is,

• Providing the User Interface

The user interface is that part of the operating system with which the user interacts with a computer. User interface functions:

• Start application programs
• Manage disks and files. We can format new disks, copy files from one disk to another, rename files, and delete files.
• Shut down the computer safely by following an orderly shutdown procedure.

There are 3 types of User Interface:

Graphical User Interface (GUI) is the most popular user interface. It takes advantages of the computer's graphics capabilities to make the OS and program's easier to use. On today's Macintoshes and PCs, GUIs are used to create the desktop that appears after the OS finishes loading into memory. On the desktop, we can initiate many actions by clicking small images called icons that represent computer resources e.g. programs, data files, and network connections.

The latest Mac OS X Lion (coming on July). Apple, Inc. introduces the first GUI to the world.

Menu-driven User Interface enable us to to avoid memorizing keywords e.g. copy and paste, and syntax i.e. set of rules for entering commands. On screen, text-based menus are used to show all of the options available at a given point. With most systems, we select an option with the arrow keys and press Enter.

Command Line User Interface require us to type commands using keywords that tell the OS what to do e.g. format or copy, one line at a time. We must observe complicated rules of syntax that specify exactly what we can type in a given place. Command-line user interfaces aren't popular with most users because they requires memorization, and it's easy to make a typing mistake. Although the commands are usually very simple e.g. copy and paste, others are more cryptic. Example of a command,

copy D:\homework.pages C:\homework.pages

This command means copies a Pages file from the disk in drive D to the disk in drive C.

I'll post the 'exploring the popular OSs' part later...