Computer Fundamentals Notes for SSC Exams: CPU, ALU and Basics

Computer fundamentals is the first and most searched topic of SSC Computer Knowledge. Questions on the CPU, ALU, control unit and the characteristics of a computer appear in every exam. These computer fundamentals notes for SSC explain the basics in simple language with tables and practice questions. After this, read the Generations of Computers Notes, Computer Hardware Components Notes and Computer Memory Notes notes.

What Is a Computer?

A computer is an electronic device that accepts data (input), processes it according to instructions, stores it and gives the result (output). The word computer comes from the Latin word computare, which means to calculate.

• Data means raw facts and figures, such as numbers or names.
• Information is the processed and meaningful form of data.
• A computer works in the IPO cycle: Input, Processing and Output (with Storage).
• Hardware is the physical part of a computer; software is the set of programs.

Characteristics of a Computer

Characteristic	Meaning
Speed	Performs millions of operations in a second
Accuracy	Gives error-free results if the input and the program are right
Diligence	Does not get tired or bored
Versatility	Can do many different tasks
Storage	Stores a huge amount of data
Automation	Works automatically once a program is given
No IQ	Cannot think on its own; it follows instructions

The famous saying "GIGO" means Garbage In, Garbage Out: if the input is wrong, the output will also be wrong.

Block Diagram of a Computer

Unit	Function
Input unit	Takes data and instructions into the computer (keyboard, mouse)
CPU (Central Processing Unit)	The brain of the computer; processes the data
Memory unit	Stores data and instructions (RAM, ROM)
Output unit	Shows the result (monitor, printer)

The CPU has three main parts: the ALU, the control unit and the registers.

Parts of the CPU

Part	Function
ALU (Arithmetic Logic Unit)	Performs arithmetic (add, subtract, multiply, divide) and logical (compare, AND, OR, NOT) operations
CU (Control Unit)	Controls and coordinates all the parts; gets the instructions from the memory and directs them
Registers	Very fast small memory inside the CPU for temporary data

• The CPU is also called the processor or the brain of the computer.
• A microprocessor is a CPU on a single chip. The first microprocessor was Intel 4004 (1971).
• The speed of the CPU is measured in hertz (MHz or GHz). The clock speed shows how many cycles the CPU completes in a second.
• A dual-core or quad-core processor has two or four processing units on one chip.

Machine Cycle

The CPU executes every instruction in four steps: fetch (get the instruction from the memory), decode (understand the instruction), execute (perform it) and store (save the result). The Von Neumann architecture uses the stored program concept, in which the instructions and the data are kept in the same memory.

Functions of a Computer (IPO and Storage)

1. Input: data and instructions are entered into the computer.
2. Processing: the CPU performs the calculations and the logical comparisons.
3. Storage: the data, the instructions and the results are stored in the memory.
4. Output: the result is shown in a useful form.
5. Control: the control unit manages the above steps in the correct order.

Von Neumann architecture (1945): a computer has an input unit, an output unit, a memory unit that stores both data and program, an ALU and a control unit. The idea of the stored program means that the program is also kept in the memory.

Advantages and Limitations of a Computer

Advantages	Limitations
Very high speed	Cannot think or take decisions on its own
High accuracy	Depends fully on the instructions given by humans
Stores a large amount of data	Needs electricity to work
Works for long hours without tiredness	Can be misused (cyber crime)
Can do many different tasks	Expensive to buy and repair for large systems
Reduces paper work	Wrong input gives wrong output (GIGO)

Hardware, Software, Firmware and Liveware

Term	Meaning
Hardware	The physical parts of the computer
Software	The programs and instructions
Firmware	Permanent software stored in ROM
Liveware (humanware)	The people who use or operate the computer: users, programmers and system analysts
Middleware	Software between the operating system and the applications
Malware	Harmful software

Data Processing Cycle

• Data collection gathers raw data from sources.
• Data preparation checks and arranges the data.
• Data input enters the data into the computer.
• Processing performs the operations to make information.
• Output and interpretation shows the result to the user.
• Storage saves the data for the future.
• A database is an organised collection of data, and a file is a collection of related records.
• A byte holds one character; a field is a group of characters; a record is a group of fields; a file is a group of records.

Processor Terms

Term	Meaning
Clock speed	The number of cycles per second in hertz (GHz)
Core	An independent processing unit inside a CPU
Thread	A sequence of instructions that can run independently
Word length	The number of bits processed at one time (32-bit or 64-bit)
MIPS	Million Instructions Per Second, a measure of CPU speed
FLOPS	Floating-point operations per second, used for supercomputers
Bus width	The number of bits that can move on the bus at one time
Moore's law	The number of transistors on a chip doubles about every two years; given by Gordon Moore of Intel
CISC	Complex Instruction Set Computer; many complex instructions
RISC	Reduced Instruction Set Computer; fewer and simpler instructions; faster

Booting and Basic Computer Operations

• Booting starts the computer and loads the operating system into the RAM.
• Cold boot starts from the power-off state; warm boot restarts a running computer using Ctrl + Alt + Delete or the Restart button.
• POST (Power-On Self Test) checks the hardware at the start.
• Shut down closes all the programs and then switches off the power safely.
• Sleep keeps the work in the RAM with low power; hibernate saves the work on the hard disk and switches off.
• Log in is to enter a user name and a password; log out is to leave the account.

Important Questions Explained

Question 1: Which part of the computer is called its brain?
Answer: The CPU (Central Processing Unit).

Question 2: What are the main parts of the CPU?
Answer: The ALU, the control unit and the registers.

Question 3: Which unit performs arithmetic and logical operations?
Answer: The ALU (Arithmetic Logic Unit).

Question 4: What does GIGO mean?
Answer: Garbage In, Garbage Out.

Question 5: What is the processed form of data called?
Answer: Information.

Question 6: In which unit is the clock speed of a CPU measured?
Answer: Hertz (MHz or GHz).

Quick Tips to Remember

• Remember the CPU as ALU + CU + registers.
• Link ALU with calculation and logic, and CU with control.
• Learn the seven characteristics, especially "no IQ" and "diligence".
• Remember data as raw and information as processed.
• Remember the machine cycle: fetch, decode, execute, store.

Common Mistakes to Avoid

• Writing the memory as a part of the CPU.
• Confusing the ALU and the CU.
• Writing information as raw data.
• Thinking that a computer can think on its own.
• Mixing the speed unit (hertz) with the memory unit (byte).

Quick Revision Points

• Computer: input, process, store, output.
• CPU = ALU + CU + registers; brain of the computer.
• ALU does arithmetic and logic; CU controls.
• Data is raw; information is processed data.
• GIGO = Garbage In, Garbage Out.

Practice Questions With Answers

1. The brain of the computer is?
   Answer: CPU (Processor).
2. Which unit performs calculations?
   Answer: ALU (Arithmetic Logic Unit).
3. Which unit controls all the other units?
   Answer: Control unit (Part of the CPU).
4. Raw facts and figures are called?
   Answer: Data (Processed data is information).
5. What is the full form of CPU?
   Answer: Central Processing Unit (Brain of the computer).
6. What does GIGO stand for?
   Answer: Garbage In, Garbage Out (Wrong input gives wrong output).
7. Which was the first microprocessor?
   Answer: Intel 4004 (1971).
8. The speed of a CPU is measured in?
   Answer: Hertz (GHz).
9. Which cycle describes the working of a computer?
   Answer: IPO cycle (Input, process, output).
10. What are the four steps of the machine cycle?
    Answer: Fetch, decode, execute, store (Instruction cycle).

More Practice Questions With Answers

1. Who proposed the stored program concept?
   Answer: John von Neumann (1945).
2. What does MIPS measure?
   Answer: CPU speed (Million Instructions Per Second).
3. Who gave Moore's law?
   Answer: Gordon Moore (Intel).
4. Which architecture has simpler and fewer instructions?
   Answer: RISC (Faster).
5. What is the people who use a computer called?
   Answer: Liveware (Humanware).
6. What is a group of fields called?
   Answer: Record (Database).
7. What is the group of records called?
   Answer: File (Data hierarchy).
8. What saves the work on the disk and switches off the power?
   Answer: Hibernate (Power option).
9. Which test checks the hardware at start?
   Answer: POST (Power-On Self Test).
10. Which mode keeps work in RAM with low power?
    Answer: Sleep (Power option).
11. How many bits are processed at a time in a 64-bit CPU?
    Answer: 64 (Word length).
12. What is a core?
    Answer: An independent processing unit inside a CPU (Dual, quad).

How to Practise This Chapter

1. Read the tables once and learn the key facts by heart.
2. Revise the quick revision points the next day.
3. Attempt the practice questions above without looking at the answers.
4. Solve a full SSC CGL Tier 1 mini mock to test your general awareness.
5. Check the previous year papers to see how SSC asks computer questions.

Related Notes and Practice Papers

• Generations of Computers Notes
• Computer Hardware Components Notes
• Computer Memory Notes
• Computer Knowledge Notes for SSC
• SSC CGL Tier 1 Mini Mock

Explore More SSC Subjects

SSC exams test many subjects, so connect this topic with the related subjects below:

• General Science Notes
• General Awareness Notes
• Quantitative Aptitude Notes
• Reasoning Notes
• Electrical Engineering (SSC JE) Notes
• All SSC subjects and notes

Frequently Asked Questions

What is a computer?

A computer is an electronic device that takes input, processes it, stores it and gives output.

What is the CPU?

The CPU is the central processing unit, the brain of the computer, which processes the data.

What are the parts of the CPU?

The CPU has the ALU, the control unit and the registers.

What does the ALU do?

The ALU performs arithmetic operations and logical operations.

What is the difference between data and information?

Data is raw facts, while information is processed data that has meaning.

What are the characteristics of a computer?

Speed, accuracy, diligence, versatility, storage, automation and no IQ.

What is GIGO?

GIGO means Garbage In, Garbage Out, which shows that wrong input gives wrong output.

What is the IPO cycle?

The IPO cycle is Input, Processing and Output, the basic working of a computer.

How many questions come from computer fundamentals in SSC exams?

Usually two or three questions come from the basics of computers.

What is the stored program concept?

The stored program concept means that both the data and the program instructions are kept in the computer memory, an idea given by John von Neumann.

What is the difference between CISC and RISC?

CISC has many complex instructions, while RISC has fewer and simpler instructions that work faster.

What is the difference between sleep and hibernate?

Sleep keeps the work in the RAM with low power, while hibernate saves the work on the hard disk and switches the computer off.