cmps 431 1.1 questons

1. What is a quick definition for an OS?

An Operating System (OS) is the software that manages a computer's hardware and acts as an intermediary between the user and the computer's physical components.

2. A computer system has what components?

Hardware, Operating System, Application Programs, and Users.

3a. Before OS Development
How used:
How programmed:

• How used: Users had exclusive access to the machine. They sat at the console and operated it manually.

• How programmed: Via physical switches (toggling bits) or by loading punched cards/paper tape directly into readers. No software interface existed.

3b. Why an OS is more efficient

Efficiency: It automates the transition between jobs, reducing "setup time" and keeping the CPU busy instead of waiting for a human to flip switches.

3c. First "Usability" Programs

The Services: Linkers, Loaders, and Libraries of common functions (like I/O routines) so programmers didn't have to rewrite code for every basic task.

3d. Batch OS & Components

• Batch OS: A system where similar jobs are grouped together and run as a single "batch" to save time.

  • i. Operator: The human who sorted jobs into batches and fed them into the computer.

  • ii. Monitor: The "resident" software that automatically switched from one job to the next.

3e. Batch OS Efficiency

Improvement: It significantly reduced idle time by removing the slow human element between individual programs.

3f. Multi-Programmed Batch OS

• Definition: An OS that keeps multiple jobs in memory at once.

  • i. Efficiency: When one job waits for I/O (like a printer), the CPU switches to another job. This maximizes CPU utilization.

  • ii. Added Functions: Job Scheduling (picking which job runs next) and Memory Management (keeping jobs separate).

3g. Interaction in Batch Systems

Level of Interaction: Zero. Users submitted a job and came back later for results. They could not interact with the program while it was running.

3h. Time Sharing (Multitasking)

The Remedy: The CPU switches between users so rapidly that each user feels they have their own dedicated machine. It allows for real-time interaction with the program.

5. What is a device controller used for? What happens if we do not have them?

What is a device controller used for?

It is a hardware component (chip) that acts as an interface between the OS and a specific piece of hardware. It handles the low-level physical details of the device so the CPU doesn't have to.

Without device controllers, the computer system would essentially break down: