Computer Awareness Quick Notes
Computer Awareness – Master Revision Sheet
(One 60-minute sweep for every RRB exam – NTPC, Group-D, ALP, JE)
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SECTION-1 : CORE CONCEPTS – TOP 30
| # | Term | One-line Key |
|---|---|---|
| 1 | Computer | Electronic data-processor (I-P-O cycle). |
| 2 | Von-Neumann | Program & data live in same memory. |
| 3 | CPU | ALU + CU + Registers; brain of PC. |
| 4 | ALU | Arithmetic & Logic operations. |
| 5 | CU | Decodes & times every micro-op. |
| 6 | Registers | Fastest memory inside CPU (MBR, MAR, PC, IR). |
| 7 | Cache | SRAM, bridges speed gap CPU-RAM. |
| 8 | Primary | RAM (volat.) + ROM (non-volat.). |
| 9 | RAM | DDR5 > DDR4 > DDR3 (5 is latest). |
| 10 | ROM | PROM ➜ EPROM ➜ EEPROM ➜ Flash. |
| 11 | Secondary | HDD, SSD, DVD, Pen-drive (permanent). |
| 12 | SSD | No moving parts; uses NAND flash; 10× faster than HDD. |
| 13 | Firmware | Software in ROM (BIOS/UEFI). |
| 14 | BIOS | First program that runs; POST & boot. |
| 15 | Bus | Data, Address, Control lines. |
| 16 | USB | Universal Serial Bus; ver.4 – 40 Gbps. |
| 17 | OS | Resource manager; types: Batch, RT, Multi-user, Multi-task, Distributed. |
| 18 | Windows | Proprietary GUI OS by Microsoft. |
| 19 | Linux | Open-source; kernel 1991, Linus Torvalds. |
| 20 | Compiler | Converts HIGH → MACHINE (whole). |
| 21 | Interpreter | HIGH → MACHINE (line-by-line). |
| 22 | Bytecode | Java → .class → JVM (WORA). |
| 23 | Machine-Language | Binary 0-1 only; CPU understands. |
| 24 | Source-Code | Human-readable instructions. |
| 25 | Virus | Self-replicating malicious code. |
| 26 | Firewall | HW/SW barrier; filters packets. |
| 27 | Encryption | Plain → Cipher; AES-256 secure std. |
| 28 | Cloud | On-demand net resources (IaaS, PaaS, SaaS). |
| 29 | IoT | Inter-connected smart sensors. |
| 30 | AI | Machines mimic human intelligence; ML & DL subsets. |
SECTION-2 : FORMULAS & SHORTCUTS
- Storage units: 1 K = 2¹⁰ = 1024; 1 M = 2²⁰; 1 G = 2³⁰; 1 T = 2⁴⁰
- N bits → 2ᴺ patterns (e.g. 8 bits = 256 values 0-255).
- Baud = symbols/sec; bps = bits/sec; bps = baud × bits/symbol.
- RAM access-time µs→ns: HDD ~10 ms = 10×10⁶ ns; SSD ~100 µs = 10⁵ ns; Cache ~1 ns.
- Throughput = (Data size × 8) ÷ Time(sec) → Mbps.
- 1 Mbps = 10⁶ bps; 1 MBps = 8 Mbps (B=Byte, b=bit).
- Hex→Binary: replace each hex digit by 4-bit (F = 1111).
- Binary→Decimal: sum bit×2ⁿ (n starts 0 right).
- Two’s complement negative: invert bits +1.
- Disk capacity = cylinders × heads × sectors × 512 B.
- Color depth: 24-bit → 16.7 M colours (2²⁴).
- Printer ppm rating: pages per minute; higher = faster.
- MTBF: Mean Time Between Failures ↑ = reliability ↑.
- Bandwidth × Delay = Bandwidth-Delay product (TCP window).
- Speed-up (Amdahl) = 1 ÷ [(1-P) + P/S].
SECTION-3 : 50 MUST-KNOW FACTS
1 First computer: ENIAC (1946) – decimal, vacuum tubes.
2 First microprocessor: Intel 4004 (1971) – 4-bit.
3 Father of Computer: Charles Babbage (Analytical Engine).
4 Lady programmer: Ada Lovelace (first algorithm).
5 Transistor invention: 1947 Bell Labs (Bardeen, Brattain, Shockley).
6 IC invention: Jack Kilby (1958).
7 Moore’s Law: transistors double ~2 yrs.
8 Super-computer PARAM (India) 1991; latest: PARAM Siddhi-AI.
9 FASTEST Indian supercomputer as on 2023: PARAM Ananta (under NSM).
10 TOP500 list uses LINPACK benchmark.
11 ASCII: 7-bit (128); Extended 8-bit (256).
12 Unicode: UTF-8 default Web; 32-bit covers all scripts.
13 Full-form www: World Wide Web; inventor Tim Berners-Lee (CERN, 1989).
14 HTTP default port: 80; HTTPS: 443.
15 HTML: Hyper-Text Markup Language.
16 XML carries data; JSON lighter for APIs.
17 OSI layers: 7 (Please Do Not Throw Sausage Pizza Away).
18 TCP: reliable, connection-oriented; UDP: fast, connection-less.
19 IP current version: IPv6 (128-bit); loopback ::1.
20 Class-A IP: 1-126 (default mask 255.0.0.0).
21 DHCP: assigns IP automatically.
22 DNS port: 53; converts domain↔IP.
23 SMTP: sends mail (port 25); POP3 receives (110); IMAP (143).
24 FTP ports: 20 (data), 21 (control).
25 Telnet port 23; SSH secure replacement port 22.
26 Wi-Fi 6 (802.11ax) top speed 9.6 Gbps.
27 Bluetooth range: Class-1 100 m; latest ver 5.3.
28 5G peak data: 20 Gbps; latency 1 ms.
29 BharatNet: NOFN – 2.5 lakh GPON fibre to villages.
30 Digital India launched 1 July 2015.
31 UMANG app: Unified Mobile Application for New-age Governance.
32 Aadhaar: 12-digit UIDAI; biometric.
33 Tally: Accounting software (Indian).
34 SAP: German ERP; modules FI, HR, MM.
35 Oracle: RDBMS; MySQL open-source owned Oracle too.
36 SQL full form: Structured Query Language.
37 Primary key: unique, not NULL; foreign key refers parent.
38 Normal forms: 1NF→5NF (BCNF in between).
39 ACID property: Atomicity, Consistency, Isolation, Durability.
40 Blockchain: distributed ledger; SHA-256 hash.
41 Cryptocurrency Bitcoin creator: Satoshi Nakamoto (2009).
42 Ransomware: encrypts data, demands money; WannaCry 2017.
43 Firewall types: Packet-filter, Stateful, Proxy, NGFW.
44 Antivirus heuristic: detects unknown by behaviour.
45 CAPTCHA:区分人类&bot (Turing test).
46 OCR: Optical Character Recognition.
47 QR-code: 2-D matrix; holds 4296 alphanum.
48 VoLTE: Voice over LTE; better than 2G/3G voice.
49 Mirroring: RAID-1; Striping: RAID-0; parity: RAID-5.
50 CMOS battery: 3 V coin cell; keeps BIOS settings alive.
SECTION-4 : PREVIOUS-YEAR TRENDS (RRB NTPC & Group-D)
• Hardware-Q ≈ 35 % (ports, memory, devices)
• Software/OS ≈ 20 % (Windows, Linux boot, function)
• MS-Office/Shortcut ≈ 15 % (Word, Excel, PPT)
• Networking/Web ≈ 10 % (HTTP, SMTP, Wi-Fi gen)
• Cyber security/Abbreviations ≈ 10 %
• DBMS/Number system ≈ 5 %
• Indian Govt IT schemes ≈ 5 %
Weightage unchanged 2016-2023 CBTs.
SECTION-5 : 100 ONE-LINER CAPSULE
1 ENIAC weighed 27 t.
2 Vacuum tubes replaced by transistors (2-gen).
3 3-gen: IC; 4-gen: VLSI/micro.
5-gen: AI/u-parallel.
4 MICR cheque code: 9-digit; Mumbai 400002 007.
5 CRT full name: Cathode Ray Tube.
6 TFT = Thin Film Transistor LCD.
7 LED screen uses Light-Emitting Diodes.
8 Plasma screen ionised gas; obsolete.
9 OLED: Organic LED – flexible.
10 Touch-screen types: Resistive, Capacitive (phones), IR, SAW.
11 Lightest storage media: DNA (experimental).
12 Blu-ray: 25 GB single layer; 50 GB dual.
13 SATA III speed: 6 Gbps.
14 NVMe over PCIe ×4 ≈ 3.5 GB/s.
15 DDR5 voltage: 1.1 V (DDR4 1.2 V).
16 Cache levels: L1 < L2 < L3 (size↑, speed↓).
17 Register size 64-bit ⇒ can address 16 EB.
18 RISC: fewer cycles/instr.; CISC: complex instr.
19 Pipeline hazards: Data, Control, Structural.
20 Superscalar: issue >1 instr./cycle.
21 USB-C reversible; supports 100 W power.
22 Thunderbolt 4: 40 Gbps, daisy-chain 4 displays.
23 HDMI type: audio+video; max 48 Gbps (ver 2.1).
4 Gbps DisplayPort 2.0 80 Gbps.
25 Scanner unit: DPI (dots per inch).
26 Plotter: vector graphics; CAD.
27 3-D printer tech: FDM, SLA, SLS.
28 Barcode first used 1974 (Wrigley gum).
29 QR invented by Denso Wave (Japan) 1994.
30 DPI vs PPI: DPI hardware, PPI digital image.
31 Laser printer parts: Drum, Toner, Fuser.
32 Page-description language: PostScript, PCL.
33 Multiprogramming: many jobs in memory.
34 Multiprocessing: many CPUs parallel.
35 Time-sharing: interactive multi-user.
36 Thread vs process: threads share address space.
37 Deadlock conditions: Mutual, Hold-wait, No-preempt, Circular.
38 Banker’s algo: deadlock avoidance.
39 Page fault: needed page not in RAM.
40 Segmentation: memory chunks of var-size.
41 Virtual memory size ≤ address bus width.
42 Windows first ver: 1985 (MS-DOS shell).
43 Linux mascot: Tux penguin.
44 macOS base: Darwin (Unix).
45 Android kernel: Linux; iOS kernel: Darwin.
46 Open-source licence: GPL, Apache, MIT.
47 Shareware: free try, pay later.
48 Firmware update called “flashing”.
49 Device driver: OS-kernel module.
50 Plug-and-play: auto-config IRQ/DMA.
51 Spreadsheet cell intersection: row-column.
52 Absolute ref in Excel: $A$1.
53 Pivot table: summarize large data.
54 VLOOKUP searches first column left→right.
55 PowerPoint extension: .pptx (Office Open XML).
56 Slide master: global template.
57 DBMS = Database + Management System.
58 Tuple = row; Attribute = column.
59 DDL: CREATE, ALTER, DROP.
60 DML: SELECT, INSERT, UPDATE, DELETE.
61 DCL: GRANT, REVOKE.
62 TCL: COMMIT, ROLLBACK, SAVEPOINT.
63 Join types: Inner, Left, Right, Full, Self, Cross.
64 View: virtual table; for security.
65 Indexing speeds search; B-tree common.
66 SQL wildcards: % (many), _ (one).
67 Top-level domain: .gov, .in, .org, .com.
68 URL parts: protocol://domain:port/path?query.
69 Cookie: ≤ 4 KB; max 50 per domain.
70 Phishing: fake mail/website.
71 Spoofing: forged sender IP.
72 Spyware: secretly records activity.
73 Trojan: looks legitimate, hidden恶意.
74 Rootkit: hides malware existence.
75 DDoS: Distributed Denial of Service.
76 Two-factor: password + OTP/hardware.
77 VPN: Virtual Private Network; tunnelling.
78 PGP: Pretty Good Privacy; email encryption.
79 HTTPS uses TLS (prev SSL).
80 WPA3 latest Wi-Fi security std.
81 BitCoin cap: 21 million coins.
82 NFT: Non-Fungible Token (ownership).
83 Edge computing: process near data source.
84 Fog: cloud-to-thing continuum.
85 Hadoop: HDFS + MapReduce; big-data.
86 NoSQL types: Key-value, Document, Column, Graph.
87 MongoDB stores BSON documents.
88 AWS: Amazon Web Services – 2006 start.
89 Azure by Microsoft; GCP by Google.
90 SaaS eg: Gmail; PaaS: Google App Engine; IaaS: EC2.
91 Digital Locker: 10 MB free space (gov.in).
92 e-Certificate = DigiLocker issued = valid legally.
93 SWAYAM: MOOCs platform (MHRD).
94 JAM Trinity: Jan-Dhan, Aadhaar, Mobile. |
95 UPI built by NPCI; PIN 4-6 digit. |
96 BHIM app: Bharat Interface for Money. |
97 Rupay: Indian card network; NPCI. |
98 FASTag: RFID toll; 96 % coverage 2023. |
99 e-KYC = Aadhaar-based paperless KYC. |
100 MeitY: Ministry of Electronics & IT (India).
SECTION-6 : COMMON CONFUSIONS CLEARED | Often Confused | Correct Fact | | RAM vs ROM | RAM volatile read-write; ROM non-volatile read-mostly. | | Virus vs Worm | Virus needs host file; Worm standalone & spreads itself. | | HTTP vs HTML | HTML is language; HTTP is protocol to transfer it. | | Firewall vs Antivirus | Firewall blocks traffic; antivirus scans files. | | IPv4 loopback | 127.0.0.1 (not 192.168.x.x). | | 1 KB | 1024 bytes (not 1000). | | Mbps vs MBps | 8 Mbps = 1 MBps. | | MS-Word extension | .docx; not .doc (2003) in new exams. | | GUI vs CUI | GUI graphics icons; CUI command only. | | Router vs Switch | Router connects networks; Switch connects devices inside LAN.
SECTION-7 : MEMORY TRICKS
1 7 OSI layers: “Please Do Not Throw Sausage Pizza Away” – Phys, Datalink, Network, Transport, Session, Presentation, Application.
2 Port-Numbers: 21-FTP, 22-SSH, 25-SMTP, 53-DNS, 80-HTTP, 110-POP, 143-IMAP – sentence: “Fifty-two shooters smacked fifty-three heroes, eighty officers, one-ten pops, one-forty-three imaps.”
3 ROM family: “Puppy Eats Every Fish” – PROM EPROM EEPROM Flash.
4 RAID levels: 0-Strip, 1-Mirror, 5-Parity; draw 0=split, 1=twin, 5=add parity star.
5 ACID: “A Cute Indian Dog” – Atomicity, Consistency, Isolation, Durability.
6 Deadlock: “M-H-N-C” – Mutual, Hold-Wait, No-preempt, Circular.
7 MS-Office shortcuts: Ctrl+S (Save), Ctrl+H (Replace), Ctrl+K (Hyperlink) – “S-H-K” sounds like ‘shock’ → remember quickly.
8 Number-system conversions: Binary→Hex: group 4 from right; Decimal→Binary: divide-by-2 stack remainders.
9 Cache levels size order: L1 < L2 < L3 – “Little, Large, Largest”.
10 Indian supercomputers: “PRIDE of PARAM Siddhi-AI” – PARAM series.
SECTION-8 : LAST-HOUR REVISION – TOP-20
1 ENIAC 1946 – first general.
2 Intel 4004 – first micro.
3 Charles Babbage – father; Ada – first coder.
4 CPU = ALU+CU+Registers.
5 Memory hierarchy: CPU-reg → Cache → RAM → SSD/HDD.
6 Storage units: 1024-based (not 1000).
7 OSI 7 layers; TCP/IP 4 layers.
8 HTTP-80, HTTPS-443, SMTP-25, FTP-21/20.
9 IPv6 128-bit; loopback ::1.
10 Wi-Fi 6 (802.11ax); Bluetooth 5.3.
11 Virus/Worm/Trojan/Ransom – know diff.
12 Firewall & Antivirus both needed.
13 BIOS/UEFI – first boot firmware.
14 RAID 0-speed, 1-safe, 5-balance.
15 ACID property – DBMS.
16 SQL: DDL-create/alter, DML-select/insert.
17 MS-Office: Ctrl+S-save, Ctrl+C-copy, Ctrl+V-paste.
18 Cloud: SaaS-Gmail, IaaS-EC2, PaaS-Google App.
19 Digital India 2015; UMANG, DigiLocker, BHIM.
20 Quick math: 8 Mbps = 1 MBps; 1 KB = 1024 B.
Now close this sheet, glance at Section-8 once more, and walk into the hall – you’re good to go!
BETA
