The words software, code and programs are often used
interchangeably. They all refers to instruction sequences that run on the hardware of a computer. They can be divided
up into two general areas: operating systems and application
programs.
Operating Systems
The operating system (OS) is essential code that a PC must have. It is stored on your hard drive. It provides the basic operating platform that brings the PC to a point where it can interpret the keyboard and mouse input and display data and images on the video display. Other programs can't run on a PC until the OS is loaded and running. DOS, Windows 95 and Windows 98 are examples of operating systems.
When an OS like Windows 98 has been loaded and is ready to go, the Windows Desktop appears. All you have to do is point and click on a desktop icon or the Start Button to select an application program you want to use and away you go!
BIOS (Basic Input Output System)
This is essential code that initializes the hardware in your PC and loads the OS. It can loosely be considered to be a part of the OS. When you first turn on your PC it is under the control of BIOS code which is stored in a special memory chip on the mother board.
The BIOS stores configuration information about all the hardware in the PC. The type of hard drive, floppy drive, video display, CD etc. is kept here so that the PC knows how to communicate with these devices. Newer BIOS code has 'auto' modes that can figure out what hardware is attached and how to communicate with it. In older BIOS, if hardware is changed without updating the BIOS the PC may not complete it's boot up cycle, and will just sit there until the new device parameters are loaded into it.
After BIOS copies the OS code from your hard drive into memory, the copy of the OS in memory takes over and finished the initialization process. When it is complete the PC is ready to use application programs.
Application Programs
These are workhorses of code. They are the ones you are probably most familiar with. They run on top of the OS and allow you to use your PC for work or play.
Word, Excel, Frame Maker, Corel Draw and PC games are a just a few examples of the thousands of Application Programs that are available to you.