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STONE RIDGE, N.Y. 12484
INSTRUCTOR: Karl Wick SEMESTER: Spring 1999
Computer Software is a collective term for all
of the instructions which make the computer do useful things for us.
Software is usually changeable by the programmer, sometimes by the user. It falls into
three basic catagories;
is a set of instructions which are the first instructions followed by the computer system after it is turned on and it has completed some basic housekeeping functions. The operating system is (supposedly) designed to let the user communicate easily and understandably with both the computer and any programs which the user needs to run.
It manages system resources like
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and it keeps everything running smoothly.
| A special program which lets the user run other programs and helps those programs to use hardware devices on the system. | Software which provides an interface between application programs and hardware |
| Software which controls the overall activity of the computer. It ensures that all parts of a computer system work smoothly together. | Controls Hardware, Runs Applications, Helps Manage Information |
There are several operating systems in common use on personal computers. The most often encountered are;
We will discuss these in more detail shortly.
These parts are called the Command Interpreter or 'Shell' and the Kernel.
The Command interpreter is the part of a computer operating system that understands and executes commands that are entered by a program or operator. It is the outermost layer of the operating system.
The Kernel is the innermost part, or core, of the operating system. It provides basic services for all the other parts of the OS.
Typically, a kernel (or any comparable center of an operating system) includes these items:
A kernel's services are requested by other parts of the operating system or by applications through a specified set of program interfaces known as system calls.
Because the code that makes up the kernel is needed almost continuously, it is usually loaded into memory in an area that is reserved and protected from being overwritten by other information.
The kernel should not be confused with the BIOS. The Kernel uses the BIOS.
The 'BIOS' or Basic Input/Output System is a collection of instructions stored in ROM (read only permanent memory) on the system motherboard. These routines perform specific functions dealing with getting information to and from the microprocessor itself. For example, a BIOS routine might do one of these things;
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The BIOS also has some routines which deal with housekeeping functions. These functions are usually run immediately after the machine is turned on they generally include (along with other functions);
BIOS is the program a personal computer's microprocessor uses to get the computer system started after you turn it on. It also manages data flow between the computer's operating system and attached devices such as the hard disk, video card, keyboard, mouse, and printer.
BIOS is an integral part of your computer and comes with it when you bring it home. (In contrast, the operating system can either be preinstalled by the manufacturer or vendor or installed by the user.) BIOS is a program that's made accessible to the microprocessor on an eraseable programmable read-only memory (EPROM) chip.
When you turn on your computer, the microprocessor passes control to the BIOS program, which is always located at the same place on EPROM.
When BIOS boots up (starts up) your computer, it first determines whether all of the attachments are in place and operational and then it loads the operating system (or key parts of it) into your computer's random access memory RAM from your hard disk or diskette drive.
With BIOS, your operating system and its applications are freed from having to understand exact details (such as hardware addresses) about the attached input/output devices. When device details change, only the BIOS program needs to be changed. Sometimes this change can be made during your system setup. In any case, neither your operating system or any applications you use need to be changed.
Although BIOS is theoretically always the intermediary between the microprocessor and I/O device control information and data flow, in some cases, BIOS can arrange for data to flow directly to memory from devices (such as video cards) that require faster data flow to be effective.
A source: Winn L. Rosch. The Winn L. Rosch Hardware Bible (Third Edition), Sams Publishing, 1994.
Both operating systems and Assembly Language programs use calls to the BIOS to accomplish their tasks. With assembly language the programmer performs all of the steps directly and individually, ie:
This gives the programmer complete flexibility of how and when things happen. It also makes for tedious programming.
An operating system might do the same task with one textual instruction;
Most early operating systems were written in assembly language (or its more primitive cousin - machine language). Modern operating systems (such as UNIX) may be written in the C or C++ languages.
Some of the system parameters which the BIOS keeps track of can be set by the user. We can view these by pressing a special combination of keys during the boot process.
When turning on and booting a machine watch for a message on the screen. It may look like this:
| Press <DEL> to enter setup |
This message will disappear after a few seconds. If you press the indicated key(s) while the mesage is displayed you will enter a special part of the system where you can view and set some of the BIOS items.
are software which usually enable us to make the computer perform a specific function or several related functions. Programs can be written by someone else and loaded into a computer, or created by the end user. In most cases it is easiest to let someone else write and debug the program for you. If you use a program which is well known and used on a lot of other computers then there is also a much greater chance that data will be transportable from one computer to another.
Applications Programs come in many varieties. The most common catagories are
There are also many sets of related programs in the form of "Suites". A suite may contain a word processor, a database, a spreadsheet, and an internet program all with a single user interface.
The "Microsoft Office" Suite which we will be using in this class is one such collection of programs.