Comparison between real time and time sharing operating system

Protection and security 

• Protection refers to a mechanism for controlling the access of program s processes, or users to the resources defined by computer system.

• The concept of protection came with the advent of multiprogramming where several processes compete for the use of CPU.

• the purpose was to confine each users program to its assigned areaof memory so that the programs cannot interface and harm each other.

• Protection in main memory is particularly important because of address translation. The purpose of protection is to allow concurrently running process to share the common physical address space.

• Protection also ensure that only process that have gained proper authorization from the operating system can operate on memory segment , the CPU, files and other resources.