This chapter is built from the official PCTB textbook Computer Science and Entrepreneurship, Class 9 (based on the Revised National Curriculum of Pakistan 2023, approved by the Punjab Curriculum and Textbook Board, Lahore). The exercise questions below are the book's own exercise questions; the answers are model answers written for this guide.
Chapter titles and exercise questions are taken from the official book's contents and exercise pages. No page numbers are claimed for individual questions.
A system is a set of components that work together to achieve a common goal. Every system has an objective (its purpose), components (its parts), an environment (everything around it that affects it), and communication between its parts. A thermostat regulating room temperature is a simple system: it senses temperature, compares it with the target, and switches heating on or off.
A computer is also a system. Its components — users, hardware and software — must work together; if one part fails, the whole system suffers. Understanding a system means understanding its parts and how they interact, not just memorising the parts.
سسٹم اجزاء کا ایسا مجموعہ ہے جو مل کر ایک مشترکہ مقصد حاصل کرتا ہے۔ ہر سسٹم کا ایک مقصد، اجزاء، ماحول اور اجزاء کے درمیان رابطہ ہوتا ہے۔ کمرے کا درجہ حرارت قابو کرنے والا تھرموسٹیٹ ایک سادہ سسٹم ہے: وہ درجہ حرارت محسوس کرتا ہے، ہدف سے موازنہ کرتا ہے اور ہیٹر آن یا آف کرتا ہے۔ کمپیوٹر بھی ایک سسٹم ہے جس کے اجزاء کو مل کر کام کرنا ہوتا ہے۔
System software runs the computer itself: the operating system (for example Windows or Linux) manages hardware and other programs, device drivers let the operating system talk to hardware, and utility software (for example Disk Cleanup or antivirus) keeps the system healthy and secure.
Application software is written for the user: word processors, browsers, games and photo editors. A simple test: if removing it would stop the computer from working, it is probably system software; if it only stops one task, it is application software.
سسٹم سافٹ ویئر کمپیوٹر کو چلاتا ہے: آپریٹنگ سسٹم ہارڈ ویئر اور پروگراموں کا انتظام کرتا ہے، ڈیوائس ڈرائیور ہارڈ ویئر سے رابطہ کراتے ہیں اور یوٹیلیٹی سافٹ ویئر سسٹم کو محفوظ اور درست رکھتا ہے۔ ایپلی کیشن سافٹ ویئر صارف کے کام کے لیے ہوتا ہے جیسے ورڈ پروسیسر، براؤزر اور گیمز۔
In the Von Neumann architecture, one single memory stores both program instructions and data. The CPU has three main parts: the Control Unit (CU) which fetches and decodes instructions, the Arithmetic Logic Unit (ALU) which does calculations and comparisons, and registers, tiny fast storage inside the CPU.
The CPU works in a cycle: fetch the instruction from memory, decode it, execute it, and store the result. Input devices send data in, output devices show results, and the bus carries data between all parts.
وان نیومن آرکیٹیکچر میں ایک ہی میموری میں پروگرام کی ہدایات اور ڈیٹا دونوں محفوظ ہوتے ہیں۔ سی پی یو کے تین اہم حصے ہیں: کنٹرول یونٹ جو ہدایات لاتا اور سمجھتا ہے، ارتھمیٹک لاجک یونٹ جو حساب اور موازنہ کرتا ہے، اور رجسٹر جو سی پی یو کے اندر تیز چھوٹی میموری ہے۔ سی پی یو کا چکر ہے: ہدایت لاؤ، سمجھو، عمل کرو، نتیجہ محفوظ کرو۔
Computers store everything in binary (base 2, digits 0 and 1). Octal is base 8 and hexadecimal is base 16 (digits 0–9 and A–F). To convert decimal to binary, divide by 2 repeatedly and read the remainders from bottom to top: 13 in decimal is 1101 in binary (8 + 4 + 0 + 1).
Binary addition, subtraction, multiplication and division follow the same ideas as decimal arithmetic, but with only 0 and 1 — and 1 + 1 = 10 in binary (0, carry 1). Text is stored as numbers too: standard ASCII uses 7 bits per character, and Unicode (for example UTF-8) can represent characters of almost every language, including Urdu. A typical integer is stored in 4 bytes.
کمپیوٹر ہر چیز بائنری (بنیاد 2، صرف 0 اور 1) میں محفوظ کرتا ہے۔ آکٹل بنیاد 8 اور ہیکساڈیسیمل بنیاد 16 ہے۔ اعشاری عدد کو بائنری میں بدلنے کے لیے 2 پر بار بار تقسیم کریں اور باقیوں کو نیچے سے اوپر پڑھیں۔ متن بھی اعداد کی صورت میں محفوظ ہوتا ہے: معیاری ASCII میں ہر حرف 7 بٹ اور یونیکوڈ میں دنیا کی تقریباً ہر زبان کے حروف آ سکتے ہیں۔ عام انٹیجر 4 بائٹ میں محفوظ ہوتا ہے۔
اس chapter کی exercise میں book کے MCQs, short questions اور long questions ہیں — تمام سوال کتاب کی exercise کے ہیں, جواب کے ساتھ.
1. The primary function of a system is:
Answer: (b) — A system exists to achieve a common goal, not to work independently.
2. One of the fundamental concepts of any system is:
Answer: (b) — Its objective — its purpose — is a fundamental concept of any system.
3. An example of a simple system is:
Answer: (c) — A thermostat regulating temperature is the book's simple-system example.
4. The basic components of a system are:
Answer: (b) — The basic components are objectives, components, environment and communication.
5. Which of the following describes the Von Neumann architecture's main characteristic?
Answer: (c) — Von Neumann architecture stores both program instructions and data in a single memory.
6. ASCII stand for:
Answer: (a) — ASCII stands for American Standard Code for Information Interchange.
7. How many bits are used in the standard ASCII encoding?
Answer: (a) — Standard ASCII uses 7 bits per character.
8. How many bytes are used to store a typical integer?
Answer: (d) — A typical integer is stored in 4 bytes.
9. Which software is used to enhance system performance and security?
Answer: (b) — Utility software enhances system performance and security (for example Disk Cleanup, antivirus).
10. Which of the following is an example of application software?
Answer: (a) — Microsoft Word is application software; BIOS, Disk Cleanup and Device Manager belong to system software.
Answer: A system is a set of components that work together to achieve a common goal.
Answer: The Von Neumann architecture has a single memory for instructions and data, a CPU (Control Unit, ALU and registers), input devices, output devices, and buses connecting them.
Answer: The four steps are: fetch the instruction from memory, decode it, execute it, and store the result.
Answer: Its key advantage is simplicity and flexibility: programs are stored in the same memory as data, so the same machine can run many different programs.
Answer: ASCII gives every character a standard numeric code so computers can store and exchange text consistently.
Answer: Unicode is a standard that assigns a unique code to characters of almost every language and script in the world, including Urdu — far more characters than ASCII's 128.
Answer: More bits give a larger range: with n bits you can represent 2 to the power n different values (8 bits give 256 values, 16 bits give 65,536).
Answer: System software runs the computer itself. Examples: an operating system (Windows/Linux) and utility software (antivirus, Disk Cleanup).
Answer: System software runs and manages the computer (operating system, drivers); application software performs a user task (word processor, browser, game).
Answer: 1100₂ + 1011₂ = 10111₂. Check: 12 + 11 = 23, and 10111₂ = 16 + 4 + 2 + 1 = 23.
Answer: 1010₂ − 0011₂ = 0111₂. Check: 10 − 3 = 7, and 0111₂ = 7.
Answer: A system is a set of interacting components working for a common goal. Its parts are its objective (purpose), components, environment (surroundings that affect it) and communication between parts. Examples: a thermostat system (sensor, controller, heater) keeps a room at a set temperature; a computer system (hardware, software, users) processes data. What matters is interaction: changing one part affects the whole system.
Answer: The Von Neumann architecture stores instructions and data together in one memory. The CPU fetches instructions from memory; its Control Unit decodes them, the ALU performs arithmetic and logic, and registers hold data being worked on. Buses carry data between memory, CPU and input/output devices. Almost all modern computers follow this design.
Answer: The CPU works in the fetch–decode–execute–store cycle: (1) Fetch: the Control Unit takes the next instruction from memory. (2) Decode: it works out what the instruction means. (3) Execute: the ALU or another unit performs it. (4) Store: the result is written back to a register or memory. The cycle then repeats for the next instruction, millions of times per second.
Answer: Unicode assigns a unique number (code point) to each character of almost every writing system. For example, the Latin letter 'A' is U+0041 and Urdu letters have their own code points, so Urdu text can be stored and exchanged like English. UTF-8 is a common Unicode encoding: ASCII characters use one byte, and other scripts use more bytes as needed, so old ASCII text still works inside Unicode.
Answer: Integers are stored as binary numbers in a fixed number of bytes — typically 4 bytes (32 bits). The bits hold the value in binary; for negative numbers, computers commonly use two's complement, where the highest bit marks the sign and the value is stored so that addition works the same for positive and negative numbers. Fixed size is why integers have a maximum value: a 32-bit signed integer ranges from about −2.1 billion to +2.1 billion.
Answer: a. Multiplication: 101₂ × 11₂. 101₂ = 5 and 11₂ = 3, so the answer is 15 = 1111₂. Working: 101 × 1 = 101, and 101 × 10 = 1010; adding gives 1111. b. Division: 1100₂ ÷ 10₂. 1100₂ = 12 and 10₂ = 2, so the answer is 6 = 110₂. Working: 12 ÷ 2 = 6 with remainder 0.
A system is components working together for a goal; software splits into system and application software; Von Neumann's single memory holds instructions and data; and everything is stored as binary, with ASCII and Unicode for text.
Revision guidance: پہلے MCQs خود حل کرو, پھر جواب ملاؤ; short سوالوں کے جواب اپنے الفاظ میں لکھ کر practice کرو; long سوالوں کے لیے ہر section کی headings اور مثالیں یاد رکھو.
سسٹم اجزاء کا مل کر مقصد حاصل کرنا ہے؛ سافٹ ویئر سسٹم اور ایپلی کیشن دو قسم کا ہے؛ وان نیومن کی ایک میموری میں ہدایات اور ڈیٹا ہوتے ہیں؛ اور ہر چیز بائنری میں محفوظ ہوتی ہے، متن کے لیے ASCII اور یونیکوڈ ہیں۔
رہنمائی: پہلے ایم سی کیوز خود حل کریں پھر جوابات ملائیں؛ مختصر سوالات کے جوابات اپنے الفاظ میں لکھ کر مشق کریں؛ تفصیلی سوالات کے لیے ہر سیکشن کی سرخیاں اور مثالیں یاد رکھیں۔
Is chapter ke topics: What Is a System? — Theory of Systems · Software: System Software and Application Software · Von Neumann Architecture and the CPU · Number Systems, Binary Arithmetic and Text Encoding · مشق
Topics (Urdu): سسٹم کیا ہے؟ — سسٹمز کا نظریہ · سافٹ ویئر: سسٹم سافٹ ویئر اور ایپلی کیشن سافٹ ویئر · وان نیومن آرکیٹیکچر اور سی پی یو · نمبر سسٹمز، بائنری حسابی عمل اور ٹیکسٹ انکوڈنگ
Revision guidance: پہلے MCQs خود حل کرو, پھر جواب ملاؤ; short سوالوں کے جواب اپنے الفاظ میں لکھ کر practice کرو; long سوالوں کے لیے ہر section کی headings اور مثالیں یاد رکھو.
Chapter-wise tests, fresh random papers اور instant score کے لیے PunjabTest.com کا میں test section دیکھو:
PunjabTest.com — Complete Guide Book • Class 9 Computer Science, Chapter 1 (official PCTB book exercise, Session 2026–27) • English + Urdu