OS Case Study #3

Name: Vena H. Ronquillo

Section: BSIT 3

Case Study #: 3

 

Multiprogramming is way to run multi programs simultaneously. It give you feel that all your programs running simultaneously. For example windows is a multiprogramming environment in which you could. Multiprogramming makes efficient use of the CPU by overlapping the demands for the CPU and its I/O devices from various users. It attempts to increase CPU utilization by always having something for Multiprogramming. Multiprogramming is a feature of an OS which allows running multiple programs simultaneously on 1 CPU. So, say, you may be typing in word, listing to music while in background IE. Time-sharing operating system (time-sharing system) - 70 since the mid - "Time-sharing" means: Time-sharing refers to the use of multiple users sharing the in Computers.

 

-Two potential problems in this kind of environment are:

1) One user can copy another user's program / memory space. This could be very detrimental if, for example, an administrator was running a decryption protocol, and another user stole the decryption program and/or key. Multiprogramming is a rudimentary form of parallel processing in which several programs are run at the same time on a uniprocessor. Since there is only one processor , there can be no true simultaneous execution of different programs. Instead, the operating system executes part of one program, then part of another, and so on. To the user it appears that all programs are executing at the same time. If the machine has the capability of causing an interrupt after a specified time interval, then the operating system will execute each program for a given length of time, regain control, and then execute another program for a given length of time, and so on. In the absence of this mechanism, the operating system has no choice but to begin to execute a program with the expectation, but not the certainty, that the program will eventually return control to the operating system. If the machine has the capability of protecting memory , then a bug in one program is less likely to interfere with the execution of other programs. In a system without memory protection, one program can change the contents of storage assigned to other programs or even the storage assigned to the operating system. The resulting system crashes are not only disruptive, they may be very difficult to debug since it may not be obvious which of several programs is at fault.

2) Resource usage may not be completely controlled, and could cause deadlock for certain users. For example, if user A had resource 1 and was waiting for resource 2 and user B had Resource 2 and was waiting for resource 1, deadlock would occur and neither user would be able to make progress in their program, no matter how many time slots they were allocated. When more than one users share it resources then it means that they are sharing computer's time. So time sharing systems allow multi-user to use computer resources by multitasking. All the users can perform different task by sharing in Software.