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Tech Mahindra · OS
Practice OS questions specifically asked in Tech Mahindra interviews – ideal for online test preparation, technical rounds and final HR discussions.
Questions
14
Tagged for this company + subject
Company
Tech Mahindra
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Subject
OS
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Go through each question and its explanation. Use this page for targeted revision just before your Tech Mahindra OS round.
A zombie process is a process that has finished execution (exit) but still has an entry in the process table because its parent has not yet read its exit status (via wait). It arises when the child ends but the parent hasn’t yet called wait, so the OS cannot release the PCB until the parent does so.
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Standard process states are Running (executing on CPU), Ready (waiting for CPU), and Waiting/Blocked (waiting for I/O or event). "Suspended" is used in some systems as an additional state when the process is swapped out, but it is not part of the classic simple lifecycle model.
Multiprogramming allows multiple programs to be in memory at once. When one program is waiting for I/O, the CPU switches to another program so the CPU stays busy. This improves utilization of the CPU and overall throughput in a system with serial I/O operations.
Virtual memory allows processes to execute even if they are partially in physical RAM by using disk space as an extension and swapping pages in and out. This gives the illusion that the system has more memory than physically present, enables more processes to run, and simplifies memory management. :contentReference[oaicite:4]{index=4}
In first-fit allocation the OS searches the free list and allocates the first block that is large enough. It is simple and fast but may leave many small leftover blocks (external fragmentation). Best-fit tries to find the smallest adequate block but can suffer from many tiny unusable fragments; worst-fit picks the largest block leaving larger smallest leftover. These trade-offs are common interview topics. :contentReference[oaicite:8]{index=8}
In Linux system directories, /etc is the standard directory where system configuration files are kept. This question tests familiarity with file system structure, which often shows up in interviews. :contentReference[oaicite:3]{index=3}
In Unix-style systems, to remove files from a directory the user must have write permission (to modify the directory contents) AND execute permission (to access the directory). A directory without execute bit might prevent access. Knowledge of file and directory permissions is a common interview topic.
Spooling stands for Simultaneous Peripheral Operations On-Line. It uses an intermediate buffer or queue so that data destined to a slower device is stored temporarily and the system can move on. This improves efficiency for devices like printers.
A correct solution to the critical-section problem must satisfy mutual exclusion (only one process at a time), progress (decide which process enters if none is in critical section) and bounded waiting (each process must wait only a bounded number of times). Infinite waiting (starvation) is not acceptable. This is a standard concurrency property.
The W^X (Write XOR Execute) policy means that memory pages are never both writable and executable at the same time. In other words a page is either writable (data) or executable (code), but not both. This mitigates a class of attacks where malicious code writes into a memory region and then executes it (such as buffer‐overflow shellcode). Many modern OS kernels and user code runtimes enforce W^X, making it harder for attackers to exploit memory corruption vulnerabilities.
A rootkit is a stealthy type of malicious software that embeds itself deep inside the operating system — often at kernel level — to gain elevated privileges, hide itself, intercept system calls or manipulate kernel data structures. Defending against rootkits requires OS features like integrity checking of kernel code and data, secure boot to verify initial code, memory protection (e.g., W^X), mandatory access control, module signing and monitoring suspicious behaviour. Also, isolating kernel modules and reducing trusted code (trusted computing base) limits the risk. Explaining how OS architecture helps mitigate rootkits shows strong interview understanding.
When an OS encounters a kernel panic or fatal error the typical steps are: 1) Immediately halt or freeze further non-critical activities to prevent corruption. 2) Log diagnostic information (stack trace, register state, memory dump) so engineers can analyse root cause. 3) Attempt automatic recovery if supported (e.g., reboot to safe mode or use a redundant node in high availability systems). 4) For critical services the OS or platform might trigger fail-over to a standby system, preserve user sessions or state if possible, and restore service quickly. 5) On restart perform integrity checks (file system check, memory diagnostic) before resuming full operations. Mentioning high-availability OS patterns (redundant kernel, live patching) adds depth.
The kernel is the heart of the OS. It handles resource management, process scheduling, memory control, device I O and communication between hardware and software.
Multiprogramming is the technique where the OS keeps multiple programs in memory and switches between them so the CPU is busy when one program waits for I O. It improves utilization of the CPU.