Public computers are open for public uses, possibly as an Interactive kiosk. There are many places one can use them, such as cybercafes, schools and libraries.
They are normally fire-walled and restricted to run only their pre-installed software. The operating system is difficult to change and/or resides on a file server. For example, "thin client" machines in educational establishments may be reset to their original state between classes. Public computers are not expected to keep an individual's data files.
A personal computer has one user who may also be the owner (although the term has also come also mean any computer hardware somewhat like the original IBM PC, irrespective of how it is used). This user often may use all hardware resources, has complete access to any part of the computer and has rights to install/remove software. Personal computers normally store personal files, and often the owner/user is responsible for routine maintenance such as removing unwanted files and virus-scanning. Some computers in a business setting are for one user but are also served by staff with protocols to ensure proper maintenance.
These are computers where different people might log on at different times; unlike public computers, they would have usernames and passwords assigned on a long-term basis, with the files they see and the computer's settings adjusted to their particular account. Often the important data files will reside on a central file server, so a person could log onto different computers yet still see the same files. The computer (or workstation) might be a "thin client" or X terminal, otherwise it may have its own disk for some or all system files, but usually will need to be networked to the rest of the system for full functionality. Such systems normally require a system administrator to set up and maintain the hardware and software.
Computers that are used just to display selected material (usually audio-visual, or simple slide shows) in a shop, meeting or trade show. These computers may have more capabilities than they are being used for; they are likely to have WiFi and so be capable of Internet access, but are rarely firewalled (but have restricted port access or monitored in some way). Such computers are used and maintained as appliances, and not normally used as the primary store for important files.
On the basis of size there are four types of computer. They are minicomputer, micro computer, mainframe computer and super computer. Super computer is the fastest, most expensive, big in size, and most powerful computer that can perform multiple tasks within no second.