The words software, code and programs are often usedinterchangeably. They all refers to instruction sequences that run on the hardware of a computer. They can be dividedup into two general areas: operating systems and applicationprograms.
Operating Systems
The operating system (OS) is essential code that a PC must have. It is stored on your harddrive. It provides the basic operating platform that brings the PC to a pointwhere it can interpret the keyboard and mouse input and display data and imageson the video display. Other programs can't run on a PC until the OS is loadedand 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 WindowsDesktop appears. All you have to do is point and click on a desktop icon or the Start Button to select anapplication 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 theOS. It can loosely be considered to be a part of the OS. When you first turn onyour PC it is under the control of BIOS code which is stored in a specialmemory chip on the mother board.
The BIOS stores configuration information about all the hardware in the PC. Thetype of hard drive, floppy drive, video display, CD etc. is kept here so thatthe 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 withit. In older BIOS, if hardware is changed without updating the BIOS the PC maynot complete it's boot up cycle, and will just sit there until the new deviceparameters are loaded into it.
After BIOS copies the OS code from your hard drive into memory, the copy of theOS in memory takes over and finished the initialization process. When it iscomplete the PC is ready to use application programs.
Application Programs
These are workhorses of code. They are the ones you are probably most familiarwith. 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 ofthe thousands of Application Programs that are available to you.