MCA DCA7105 UNIX & SHELL PROGRAMMING

Description

SESSION	FEB-MARCH 2026
PROGRAM	MASTER OF COMPUTER APPLICATIONS (MCA)
SEMESTER	III
COURSE CODE & NAME	DCA7105 UNIX & SHELL PROGRAMMING

 

 

Assignment Set – 1

 

Q.1. Differentiate between foreground and background processes and daemon processes in Unix. What are system calls? Explain the functions of fork(), exec(), open(), read(), and write().

Ans 1.

Foreground, Background, and Daemon Processes

In Unix, a foreground process is executed directly within the terminal session. It is present in the shell till it’s finished. The user has to remain patiently waiting for it to complete before entering another command. It is impossible to use the terminal. As an example, the cat command largefile.txt ensures that the terminal is busy until the file output has been completed.

The background process is not interfering with the terminal. It allows the user to continue working as it runs. The script is sent to the

 

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Q.2. What are the different process states in UNIX? Explain each state. What are signals in UNIX? Explain common terminating signals such as SIGKILL, SIGTERM, and SIGSEGV.

Ans 2.

Process States in UNIX

Every single process that runs Unix goes through a set of state changes throughout its life. The operating system scheduler manages the process based upon available resources as well as system-related events.

The term “running state” refers to the way in which the program is currently executing within the CPU. On a single core system it is possible for only one application to be running at a time.

Ready (Runnable) state means the process is now ready to start

 

 

 

Q.3. Explain User Authentication Mechanisms in UNIX with reference to PAM (Pluggable Authentication Modules) and SSH. Describe how password-based and public key authentication work in SSH.

Ans 3.

PAM – Pluggable Authentication Modules

PAM is a flexible framework used in Unix as well as Linux systems that handles the authentication of users in a modular and flexible manner. Prior to PAM was introduced, all applications that required authentication had to implement its own authentication code. PAM simplifies the process by offering the standard interface applications are able to use, but the authentication process itself is

 

 

Assignment Set – 2

 

 

Q.4. Explain the different types of shells in UNIX. Describe the features of Bourne shell (sh), Bourne Again shell (bash), Z shell (zsh), Korn shell (ksh), and C shell (csh).

Ans 4.

Introduction to Unix Shells

A shell within Unix is a command-line interpreter that connects users with the kernel. It executes commands entered via interactively or scripts. Unix offers a variety of shells that have various features. The choice of shell affects both performance and portability of scripts.

1. Bourne Shell (sh)

The Bourne shell, invented by Stephen Bourne at Bell Labs in 1979, was the first Unix shell. It’s compatible with virtually every Unix and Linux systems at the /bin/sh directory. It has basic scripting

 

 

Q.5. What are the three standard file descriptors in UNIX and what do they represent?

Ans 5.

Introduction to File Descriptors

In Unix, a file-descriptor (FD) is an integer with a negative value that can be used by an operating system to identify the open file or resource within a process. When a process opens a file, creates pipes, or creates a network connection, the kernel returns a file descriptor that the process

 

 

 

Q.6. Explain static and dynamic memory allocation in UNIX-based C programs with their characteristics and examples of how each is used.

Ans 6.

Memory Allocation in Unix-Based C Programs

Memory management is an essential aspect of Unix-based C programming. C provides direct control over memory using dynamic as well as static allocation, and understanding both is essential for reliable systems development.

Static Memory Allocation

Static memory allocation