IBPS SO Professional Knowledge - IT Officer (Scale I) Syllabus

How many usable host addresses are in a /24 subnet, and what is the formula?

A /24 has 8 host bits, giving 2^8 = 256 total addresses and 256 - 2 = 254 usable hosts. The general formula is (2^h) - 2 usable hosts, where h is the number of host bits (subtracting network and broadcast addresses).

What are the private IPv4 address ranges defined by RFC 1918?

10.0.0.0 to 10.255.255.255 (/8), 172.16.0.0 to 172.31.255.255 (/12), and 192.168.0.0 to 192.168.255.255 (/16).

What is the difference between a routing protocol and a routed protocol, with examples?

A routed protocol carries user data and is routed across networks (e.g., IP). A routing protocol is used by routers to exchange path information and build routing tables (e.g., RIP, OSPF, BGP, EIGRP).

Compare TCP and UDP transport protocols.

TCP is connection-oriented, reliable, ordered, with flow/congestion control and error recovery (used for web, email, file transfer). UDP is connectionless, unreliable, faster, with no guaranteed delivery (used for streaming, DNS, VoIP).

What are the default port numbers for HTTP, HTTPS, FTP, DNS, and DHCP?

HTTP: 80, HTTPS: 443, FTP: 20 (data) and 21 (control), DNS: 53, DHCP: 67 (server) and 68 (client).

What is the purpose of DNS and DHCP?

DNS (Domain Name System) translates human-readable domain names into IP addresses. DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses and network configuration (subnet mask, gateway, DNS) to hosts on a network.

What is the four-step DHCP address assignment process?

DORA: Discover (client broadcasts request), Offer (server offers an IP), Request (client requests the offered IP), Acknowledge (server confirms the lease).

At which OSI layers do a hub, a switch, and a router operate?

A hub operates at the Physical layer (Layer 1), a switch operates at the Data Link layer (Layer 2, using MAC addresses), and a router operates at the Network layer (Layer 3, using IP addresses).

Name common network topologies and a key property of the star topology.

Common topologies: bus, star, ring, mesh, tree, and hybrid. In a star topology all nodes connect to a central hub/switch; failure of one cable affects only one node, but failure of the central device brings down the whole network.

What is the difference between symmetric and asymmetric (public-key) cryptography?

Symmetric cryptography uses a single shared secret key for both encryption and decryption (e.g., AES, DES) and is fast. Asymmetric cryptography uses a public/private key pair (e.g., RSA), where one key encrypts and the other decrypts, solving key distribution but being slower.

What is the difference between a stateless (packet-filtering) firewall and a stateful firewall?

A stateless firewall inspects each packet independently against rules (source/destination IP, port). A stateful firewall tracks the state of active connections and allows return traffic for established sessions, providing more intelligent filtering.

What is the difference between symmetric encryption and hashing?

Symmetric encryption is reversible (data can be decrypted with the key) and provides confidentiality. Hashing is a one-way function producing a fixed-length digest (e.g., SHA-256), is irreversible, and is used for integrity verification, not confidentiality.

What are the typical states of a process in process management?

New, Ready, Running, Waiting (Blocked), and Terminated. A process moves between these states as it is created, scheduled, executes, waits for I/O, and finishes.

Compare FCFS, SJF, and Round Robin CPU scheduling algorithms.

FCFS executes processes in arrival order (non-preemptive, can cause convoy effect). SJF runs the shortest job next (minimizes average waiting time but can starve long jobs). Round Robin gives each process a fixed time quantum cyclically (preemptive, good for time-sharing).

What are the four necessary (Coffman) conditions for a deadlock?

Mutual exclusion, Hold and wait, No preemption, and Circular wait. All four must hold simultaneously for a deadlock to occur.

What is a semaphore, and what are the two types?

A semaphore is an integer variable used for process synchronization, accessed via wait (P) and signal (V) operations. A binary semaphore (mutex) takes values 0 or 1 for mutual exclusion; a counting semaphore can take any non-negative value to manage a set of identical resources.

What is the difference between a mutex and a semaphore?

A mutex is a locking mechanism that allows only one thread access and must be released by the same thread that acquired it (ownership). A semaphore is a signaling mechanism (a counter) that can allow multiple threads and can be signaled by any thread.

What is virtual memory and how does paging support it?

Virtual memory lets a process use an address space larger than physical RAM by keeping parts on disk. Paging divides logical memory into fixed-size pages and physical memory into frames; a page table maps pages to frames, and pages are swapped in/out on demand (demand paging).

What is a page fault, and name two page replacement algorithms.

A page fault occurs when a process accesses a page not currently in physical memory, requiring the OS to load it from disk. Page replacement algorithms include FIFO, LRU (Least Recently Used), and Optimal (replace the page not used for the longest future time).

What is Belady's anomaly?

Belady's anomaly is the phenomenon where increasing the number of page frames results in more page faults instead of fewer. It can occur with the FIFO page replacement algorithm but not with stack-based algorithms like LRU or Optimal.

Compare the disk scheduling algorithms FCFS, SSTF, and SCAN.

FCFS services requests in arrival order. SSTF (Shortest Seek Time First) services the request closest to the current head position (can cause starvation). SCAN (elevator) moves the head in one direction servicing requests, then reverses, giving more uniform wait times.

What is the difference between internal and external fragmentation?

Internal fragmentation is wasted space inside an allocated block (allocated memory larger than requested, common in paging). External fragmentation is free memory scattered in small non-contiguous blocks too small to satisfy requests (common in variable partitioning/segmentation).

Compare arrays and linked lists in terms of access and insertion.

Arrays allow O(1) random access by index but O(n) insertion/deletion (shifting elements) and have fixed/contiguous memory. Linked lists allow O(1) insertion/deletion at a known node but O(n) sequential access, with dynamic, non-contiguous memory.

What is the difference between a stack and a queue?

A stack is a LIFO (Last In First Out) structure with push/pop at one end. A queue is a FIFO (First In First Out) structure with enqueue at the rear and dequeue at the front.

What is the difference between a binary tree and a binary search tree (BST)?

A binary tree is any tree where each node has at most two children. A BST is an ordered binary tree where, for every node, all left-subtree values are smaller and all right-subtree values are larger, enabling O(log n) average search.

State the average and worst-case time complexities of QuickSort and MergeSort.

QuickSort: average O(n log n), worst case O(n^2) (already sorted/poor pivot). MergeSort: O(n log n) in all cases (best, average, worst) but needs O(n) extra space.

What is the time complexity of binary search and what is its prerequisite?

Binary search has O(log n) time complexity. Its prerequisite is that the array/list must be sorted, since it repeatedly halves the search interval by comparing with the middle element.

Name and define the four core principles of Object-Oriented Programming.

Encapsulation (bundling data and methods, hiding internal state), Abstraction (exposing only essential features), Inheritance (a class deriving properties from another), and Polymorphism (one interface, many forms, e.g., method overloading/overriding).

What is the difference between compile-time and run-time polymorphism?

Compile-time (static) polymorphism is resolved during compilation via method overloading or operator overloading. Run-time (dynamic) polymorphism is resolved during execution via method overriding using inheritance and virtual functions/dynamic dispatch.

List the main phases of the SDLC and compare the Waterfall and Agile models.

SDLC phases: requirement analysis, design, implementation/coding, testing, deployment, maintenance. Waterfall is sequential and rigid with phases completed before the next begins. Agile is iterative and incremental, delivering working software in short sprints with continuous feedback.

In cloud computing, what do IaaS, PaaS, and SaaS provide? Give the difference between a hypervisor's Type 1 and Type 2.

IaaS provides virtualized hardware (servers, storage); PaaS provides a development platform/runtime; SaaS provides ready-to-use applications over the internet. A Type 1 (bare-metal) hypervisor runs directly on hardware; a Type 2 (hosted) hypervisor runs on top of a host operating system.