Installing and Uninstalling

COMP1260 > Installing and Uninstalling

Introduction Every program that resides on your computer can be represented as a collection of files. Files are chunks of data that your computer reads when it runs the program. Installing refers to the process of adding a new program to your computer. In general, installing has two main purposes: to make a copy of all of the files that make up the new program, and store them on your hard drive. to configure your settings so that the new files will ready to run on your computer. Similarly, when you want to remove a program from your computer, the files that make up the program need to be deleted. Uninstalling refers to the process of removing a program from your computer. In general, uninstalling has two main purposes as well: to delete the files that make up the program you are removing. to return your system's settings back to the way they were before you installed the program.

...by students Like most programs, Operating Systems also need to be installed. Being some-ought of a computer geek, I attempted to install Linux on my computer several years ago. It worked beautifully. I was able to configure things so that when my computer started up, I could choose whether I wanted to use Linux or use Windows. After tinkering around for a while, I decided that I would try to remove (uninstall) Linux, leaving the Windows part of my hard drive intact. After some initial unsuccessful "Googling," I discovered that there was no real automatic way to do this, and endeavoured to remove the Linux files myself. The next time I started my computer, I was greeted with a friendly "Error: Operating System not found." message. It turned out that when I had removed the Linux files, I had also removed the files for a little program that let me select which operating system to start. Eventually, I figured out that if I reinstalled Linux, this program would also be reinstalled. Fortunately, it automatically detected the Windows files on my hard drive, and I was able to use my computer again (but Linux is here to stay...).

Installing

Why do we have to install software?

Some of the files that make up a program are called executable files. These files contain instructions that tell the computer what to do. The CPU can only receive instructions from devices that are directly wired to it, like the computer's memory (RAM). Because of this, instructions from a program's executable files must be transferred into memory before the program can run. We cannot always leave a program in memory all the time, because other programs also need memory space to run. In addition, memory is erased every time the computer is turned off. Although we can transfer files from CDs or flash drives into memory, this would mean that we would have to insert the CD or plug in the flash drive every time we wanted to run the program. Hard drives, on the other hand, are always connected to the computer. This makes it much more convenient to copy the program to the hard drive before it is run.

Degree of Installation

Not all of a program's files need to be copied to your hard drive in order for it to run. Here are several examples:

• In cases where hard drive space is tight, a CD can be used in conjunction with the hard drive. A portion of the files can copied to the hard drive, while others can be read into memory from the CD as they are needed. This scheme allows the program to run without occupying a large amount of space on your hard drive. Once again, the downside is that it requires you to insert a CD every time you would like to run the program. This approach is becoming less common as hard drive sizes grow.
• Sometimes, many machines run the same software. This is often the case in computer labs. Although it is possible to install the software on each individual machine, this can be a tedious, time consuming process. Since all of the machines are running the same program, it would be very convenient if we could just install the software in a central location that can they can all access. This can be done using a special machine called a server. Every machine in the computer lab is connected to the server (through a network - a bunch communication lines between computers). The software that you want to run is installed on the server. Each machine can talk to the server, and transfer the instructions needed to run the program into its own memory. This allows the machines to run programs that have not even been (locally) installed. Although this approach slows down programs a little bit, servers are often very powerful machines, capable of talking to many computer at once (through a very fast connection).

Approaches to Installation

Ubuntu Linux Package Installer

• The Linux operating system installs software as "packages." A package is just another name for a bundle of files that make up a computer program. Packages are arranged in a hierarchy. That is, some packages may require that others are installed before they can run. These, in turn, may require other packages in order to run. In many versions of Linux, packages are installed using a single installation program. This program lists various packages that available for installation. When you select a package to install, it will determine which other packages are required in order for it to run. While this process sounds quite complicated, it actually makes very efficient use of hard drive space. Only packages that are needed to run a program are copied to your hard drive. When you uninstall a package, you can use the installation program to determine which packages are no longer needed, and remove them.

• Apple's Macintosh computer systems support the use of disk images as a method of installation. A disk image is a collections of files that have been compressed and packaged together in a container file. To install an application from a disk image, you open the image and drag and drop its contents onto the desktop. All of the associated program files are copied to your computer in the background. The disk image can then be removed.

• Microsoft Windows systems often make use of a program called the Microsoft Installer. Programmers who create software can package their programs in a special Microsoft Installer file (often with the file extension ".msi"). The Microsoft Installer program reads these packages and takes you through a number of standard steps to install the program. It will often prompt for the location that you wish to install the program's files to, the place you would like to put the program's icons in the start menu, and whether or not you would like to create a desktop short-cut to the program. Since the Microsoft Installer resides on almost every new Windows system. This saves programmers a lot of time, because they do not have to worry about programming the computer to install their application.

Uninstalling

Why do we have to uninstall software?

When you are done with a program, and would like to remove it from your computer, the files that make up the program must be removed. The installation process can store files in various locations on your machine. For example, certain files may need to placed in a specific location so that the Operating System knows where to find them when your program is run. Files for short-cuts, icons or (on a Windows machine) start menu items will also need to be placed so that the Operating System can add them to your desktop.

Approaches to Uninstallation

• As mentioned above, program files are not necessarily stored in one central location during the installation process. Rather than have you keep track of all of these files on your own, many software companies provide an uninstalling program that knows where to find them. This uninstaller keeps a list of the locations of program files, so that they can be removed automatically.
• Manually deleting files is always an alternative, but should be taken as a method of last resort. It is often difficult to be certain that you have deleted all of the files belonging to a program. In addition, some extraneous settings that were modified when the program was created may be left intact.
  • For example, the Microsoft Windows Operating System stores important settings in a big database file called the registry. Programs that run on the computer also store information in the registry. Every time the program is run, Windows looks through the registry and finds the settings that the program needs. When you manually delete a program, the files are gone, but the registry entries remain. If too many of these entries build up, they can begin to slow down your computer. Uninstaller programs in Windows will typically maintain a list of all the registry entries that were made during the installation, and remove them automatically.
• Formatting is a process that erases the entire contents of a disk. Anything from a flash drive to a hard drive can be formatted. Formatting is often useful for larger (or last resort) uninstallation tasks, such as removing an operating system. Operating systems on their own cannot really be uninstalled - they are vital to the functioning of your computer. However, any program that resides on your machine - including the operating system - is really just a bunch of files on your hard drive. These files can be erased. In this sense, formatting is similar to uninstalling. However, it is worth noting that formatting is much more destructive than a normal uninstallation process. Few the software settings on your computer really need to be returned to a previous state - everything is just erased.

Further Readings

Installing Windows Software:

• http://www.jegsworks.com/Lessons/lesson12/lesson12-5.htm
• http://www.microsoft.com/windowsxp/using/setup/hwandprograms/installprog.mspx

Installing Mac Software:

• http://guides.macrumors.com/Installing_Applications_in_Mac_OS_X

Installing Linux Software:

• http://www.control-escape.com/linux/lx-swinstall.html

References

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