Unit 1 - Operating System Overview - 2 marks solution

1.        List the elements of a computer system.

2.        What are the two modes in which a program can execute? Compare them.

                User mode – Task / process is executed on behalf of user

                Kernel mode – Task / process is executed on behalf of the OS

3.        What is an operating system?

An operating system is a program that manages a computer’s hardware / resources. It provides the interface between the user and the computer hardware. It also controls the execution of application programs and acts as an interface between applications and the computer hardware.

1.        State the functions of an operating system.

2.        What are the main purposes of operating system?

a.    Provide interface between user and computer hardware

b.    Manage all resources of the computer

c.    Support for installing and executing application programs

3.        List the services of operating system.

a.    Program execution

b.    Access to I/O devices

c.    Controlled access to files

d.   System access

e.    Error detection and response

f.    Accounting

4.        What is an instruction execution?

Program consists of a set of instructions stored in memory. Processor executes a program by executing the set of instructions. Instruction execution consists of two steps – FETCH instruction from memory one at a time and EXECUTE. Processing required for a single instruction is called an instruction cycle.

5.        List the categories of Processor action.

1.    Processor-memory: Data transfer from processor to memory or from memory to processor.

2.    Processor-I/O: Data transfer between a peripheral device (I/O module) and the processor.

3.    Data processing: processor performs arithmetic / logic operation on data.

4.    Control: An instruction that may alter the sequence of execution.

23.     List the three types of interface in a computer system.

a.    Instruction Set Architecture (ISA) – set of instructions that a computer can execute

b.    Application binary interface (ABI) – provides binary portability across programs

c.    Application programming interface (API) – specifies a set of functions that are available to an application programmer. They provide support for programs to access the hardware resources and services available in a system through the user Instruction set architecture (ISA) supplemented with high-level language (HLL) library calls.

24.     What is an API? List the common API available for application programmer.

Application Programming Interface (API) specifies a set of functions that are available to an application programmer. They provide support for programs to access the hardware resources and services available in a system through the user Instruction set architecture (ISA) supplemented with high-level language (HLL) library calls. Three of the most common APIs available to application programmers are

a.    Windows API for Windows systems,

b.    POSIX API for POSIX-based systems

c.    Java API for programs that run on the Java virtual machine.

25.     State the advantage of using API over system calls.

a.    Program portability – Programs using Application Programming Interface (API) can be compiled and run on any system that supports the same API. When system calls are used, the programs can be run on systems supporting the same Instruction Set Architecture (ISA) only.

b.    Difficulty – System calls are more detailed and difficult to work with than API

26.     What are the three methods used by programs to pass parameters to OS?

Three general methods are used by programs to pass parameters to the operating system.

1.    Pass the parameters in registers.

2.    Store the parameters in a block, or table, in memory, and the address of the block is passed as a parameter in a register

3.    Programs can push parameters into stack and OS can pop the parameters.

27.     What are system programs?

System Programs are the programs that are required to run the system. They provide a convenient environment for program development and execution. Example – System programs for file management are used to create, delete, copy, rename, print, dump, list, and generally manipulate files and directories.

28.     What are system utilities?

System utilities are application programs that are often supplied along with the operating system to solve common problems, or perform common operations. Programs include web browsers, word processors and text formatters, spreadsheets, database systems, compiler compilers, plotting and statistical-analysis packages, and games.