Module 1: Using Computers, LANs, and Email for Academic Coursework

What Happens When You Turn Your Computer On

A computer is a tremendously complex machine. Luckily, much of this complexity is hidden from the user. Most of us non-computer scientists have only a hazy understanding of how a computer actually works. Following is a very simplified explanation of what happens when you start your computer--in layman's terms.

When you turn the power on in your computer the current enters the motherboard. The ROM chip, which is built into the motherboard, reads and performs its instructions. Basically these instructions are to check the computer system for faults and to check for internal and external components such as the keyboard and mouse. If the necessary components are present and functioning properly, the ROM then searches the hard disk drive for the operating system. When it locates the operating system, it boots this system. This means that the computer loads the operating system into the RAM. By this time, the CPU is in action and is coordinating the actions of the computer components and the operating system draws the computer desktop on the monitor screen. The user now has the ability to interface with the computer to accomplish some task or work.

If the user wants to write a letter to his mother, he must open the specific computer application to perform a task such as Microsoft Word. When this application opens, it also loads into the RAM. When the user begins to use the application, the data being entered and manipulated also loads into RAM. The CPU is actively at work moving data to and from the hard disc drive and to the computer components needed to manipulate the data, for example the keyboard, mouse, and monitor.

At this point the data is at risk. If it has not been saved to the hard disk drive, it can be lost if the power fails or the computer crashes or freezes. However, if the data has been recently saved to the hard disk or to some other storage device (e.g., a flash memory drive), only changes that have taken place since the save will be lost. Because RAM is a risky place to store information, some software applications allow users to set a time limit for the computer to automatically save data. In effect, these "auto saves" keep moving data from RAM to a permanent storage device where they will not be affected by power failures or computer crashes.