Chapter 5: Programming Concept

Programming Concept

Computer Program

  • Set of instructions for specific tasks.
  • Written in programming language.
  • Compiled to machine code or interpreted.
  • Software includes programs, libraries, data.

Characteristics of a Good Computer Program:

  • Portability: Runs on different platforms with minimal changes.
  • Readability: Clear logic, easy for programmers to understand.
  • Efficiency: Uses processing time and memory effectively.
  • Structural: Divides tasks into independent subtasks.
  • Flexibility: Handles changes without full rewrite.
  • Machine Independence: Runs on different systems.
  • Cost Effectiveness: Measures overall cost and human effort.

Introduction to Programming Language

  • Designing, writing, testing, and maintaining code.
  • Creating instructions for computers to interpret and execute.
  • Developing software applications, websites, games, etc.
  • Involves algorithms, logic, and commands for specific tasks.
  • Language used by human is natural language, and language used by computer is programming language or computer language.
  • Writing a program is known as programming or coding.
  • Formal system for communicating instructions to computers.
  • Intermediary between human understanding and machine execution.
  • Enables software creation through written code.
  • Wide range of syntax, features, and paradigms.
  • Example of programming language are:
    • Python
    • Java
    • C/C#
    • C++
    • Ruby
    • JavaScript, etc.


 Low level, High level, 4 GL Programming Language (Types of Programming Language)

  • Classified to two Categories: High Level and Low Level Language.
  • Internally using language by computer itself is low level language
  • Mathematical expression and structure close to English is a high level language.

1. Low Level Language
  • Close to machine codes (0s and 1s).
  • Programs in binary form.
  • Requires hardware-specific knowledge.
  • Classified into two groups:
a) Machine Language
  • Uses 0s and 1s, readable by hardware.
  • Consists of Operation code and Operand.
    • Directly readable by CPU, speedy processing.
    • Prone to human errors due to binary representation.
    • Detecting/correcting errors is challenging and time-consuming.
  • Merit of Machine Language:
    1. Directly understands by CPU.
    2. It takes less time to execution.

    Demerit of Machine Language:

    1. Machine dependent.
    2. Difficult to program
    3. Difficult to modify
    4. Hardware knowledge required.
    5. Difficult to find out the errors.
b) Assembly Language
  • Closest to machine language, uses alphabets and numbers.
  • Uses MNEMONIC codes for instructions.
  • Assembler translates symbolic code to machine instructions.
  • Source code written in symbolic language.
  • Object code generated by the assembler.
  • Examples: CLA (Clear and Add), STA (Store), ADD, SUB.
  • Easier than machine language, yet cumbersome.
  • Error detection and fixing is easier than machine code.
  • Still more challenging than high-level languages.

Merit of Assembly Language:

  1. Easier to understand and use than machine language.
  2. Easier to locate and remove the errors.
  3. It is easier to modify.
  4. It is easy to re-locatable.

Demerit of Assembly Language:

  1. It is machine dependent.
  2. Detailed knowledge of hardware is required.
  3. It uses machine level coding.
  4. Language processor (Assembler) is required to translate the coding.
2. High Level Language
  • Closer to human language, it follows syntax rules.
  • Converted to machine-readable format.
  • Source code in high-level language.
  • Object code after conversion.
  • Compilation done by compiler/interpreter.
  • High-level languages are usually machine independent.
  • Easier to learn and faster to write than symbolic.
  • Better documentation and easier maintenance.

Merit of High level language:

  1. Machine independent.
  2. Easy to write and learn then low level language.
  3. Easy to find out and remove the mistakes.
  4. High level programs are easy to maintain.
  5. Better documentation.

Demerit of High level language:

  1. Execute very slowly.
  2. Need language processor (Compiler, Interpreter) to translate the program.
  3. Some programs cannot be solved with these languages.
  4. Lower efficiency.
  5. Less flexibility.
a) Third Generation Language (3GL)
  • Procedure-oriented for solution steps.
  • Sequential instructions needed.
  • Vocabulary: keywords and symbols.
  • Programs written using words, symbols, rules.
  • Also known as Procedure-oriented Languages

Merit of third generation language are:

  1. English-like statements, user-friendly.
  2. Faster program development.
  3. Ease of understanding and modification.
  4. Simple syntax error detection and debugging.
  5. Standardized and machine-independent.
  6. Examples: C, COBOL, FORTRAN, PASCAL, etc.

Demerit of third generation language are:

  1. Complexity for beginners
  2. Learning curve
  3. Hardware dependency
  4. Limited abstraction
  5. Efficiency concerns
  6. Challenging debugging
  7. Less control over hardware
  8. Limited portability
  9. Performance trade-offs
b) Fourth Generation Language (4GL)
  • Closer to natural language than 3GLs.
  • No detailed step-by-step instructions.
  • Descriptive approach for results.
  • Often database-oriented.
  • Users can create own applications.
  • English-like syntax.
  • Examples: SQL PLUS, HTML, PHP.
  • Application-specific and problem-solving.
  • Known as Problem-oriented Languages.

Merit of fourth generation language are :

  1. No need to know machine details.
  2. Variety of languages available.
  3. Easy bug detection and debugging.
  4. English-like syntax, user-friendly.
  5. Faster and easier coding.
  6. Supports OOP and code reusability.

Demerit of fourth generation language are :

  1. Needs a compiler/interpreter for conversion.
  2. Conversion and execution time.
  3. Less efficiency than machine language.
  4. Inefficient resource usage.

Difference between 3GLs and 4GLs

Basis 3GLs 4GLs
Focus Emphasize procedure and algorithms. Emphasize on end-user outcomes and data handling.
Nature Low-level languages, closer to machine code. High-level languages, abstracted from machine code.
Abstraction Moderate level of abstraction. High level of abstraction.
Syntax Complex syntax requiring detailed coding. User-friendly, more natural language-like.
Syntax Suitable for system-level programming and complex applications. Designed for database querying, reporting, and rapid application development.
Examples C, C++, Java, Fortran. SQL, Python (in certain contexts), visual programming tools.


c) Fifth Generation Language (5GL)
  • Known as Natural language, artificial language.
  • Natural languages: Human languages like Nepali, English.
  • Artificial languages: C, C++, Java, used by computers.
  • Fifth generation computers: Aim to understand human languages.
  • Fifth generation language: For natural interaction, AI, neural networks, expert systems.
  • LISP and PROLOG: Examples of present-day natural languages.

Merit of fifth generation language are:

  1. Ease of Use
  2. Wide Adoption
  3. Rich Expression
  4. Contextual Understanding
  5. Flexibility
  6. Inclusivity
  7. Cognitive Load Reduction
  8. Natural Interaction
  9. Efficiency for Certain Tasks
  10. Communication with Non-Programmers

Demerit of fifth generation language are: 

  1. Complexity
  2. Limited Precision
  3. Learning Curve
  4. Performance Overhead
  5. Dependency on AI
  6. Resource Intensive
  7. Potential Ambiguity
  8. Limited Optimization
  9. Compatibility
  10. Reliance on Infrastructure

Compiler, Interpreter and Assembler (Language Translator)

  • Language translator: Converts text or speech between languages.
  • Maintains meaning and context.
  • Bridges language barriers in various areas like business, travel, etc.
  • Human or machine-based translation.
  • Enables effective cross-cultural communication.


  • Translates assembly language to machine language.
  • Takes assembly language program as input.
  • Produces machine language program as output.
  • Converts human-readable code to binary.
  • Essential for programming in low-level languages.


  • Translate one line at a time.
  • Execute each line immediately.
  • No object program generated.
  • Slower and less efficient.
  • Suitable for testing and learning.
  • Ideal for logical correctness checks.
  • Compilation is postponed.
  • Beneficial for beginners and learners.


  • Translates high-level programs to machine codes.
  • Converts entire programs, not just single statements.
  • Source program becomes object program.
  • Errors must be fixed before translation.
  • Specific to the language it’s designed for.
  • Different compilers for different languages.
  • Produces binary codes for execution.

Difference Between Compiler and Interpreter

Compiler  Interpreter
Translates the entire program before execution. Translates one line at a time, executing immediately.
Generates an object program (machine code). No separate object program generated.
Detected errors only after compilation. Detects errors line by line during execution.
Produces faster execution as code is pre-translated. Slower execution due to on-the-fly translation.
Used for languages like C, C++, Java. Used for languages like Python, JavaScript.


Syntax, Semantic and Runtime errors

  • Vocabulary and rules define syntax.
  • Syntax is the grammar of the language.
  • Specifies allowed instruction structures.
  • Semantics assigns meaning to words/symbols.
  • Types of programming errors.

Syntax Error:

  • Deviation from correct syntax leads to errors.
  • Detected by the compiler during compilation.
  • Program terminates, displays error messages.
  • Examples: Misspelled names, missing semicolons, wrong brackets, incorrect statement formats.

Semantic Error:

  • Related to program logic.
  • Causes incorrect program operation.
  • Program doesn’t terminate abnormally.
  • Example: Incorrect formula like I = (P * T + R) / 100 for simple interest.
  • Also called logical errors.

Runtime Error:

  • Detected during program execution.
  • Program compiles and runs but produces wrong results.
  • Caused by data type mismatches.
  • Challenging to identify and fix.
  • Examples: Dividing by zero, accessing non-existent files.


Program Design tools

  • Aid in planning software before coding.
  • Include flowchart, pseudocode, UML, and interface tools.
  • Enhance structure, logic, and user interface design.
  • Contribute to efficient development and collaboration.


  • Step-by-step problem instructions.
  • Written using programmer’s language.
  • Not directly computer-tested.
  • Vital documentation role.

Characteristic of algorithm are:

  1. An algorithm must be simple and in easy language.
  2. An algorithm should have finite number of steps.
  3. The algorithm can be easily modified.
  4. The algorithm should be able to produce accurate result.


  • Efficiency: Optimized solutions.
  • Accuracy: Minimized errors.
  • Reusability: Applicable to similar problems.
  • Scalability: Works for varying input sizes.
  • Logic Clarity: Step-by-step understanding.
  • Problem Solving: Systematic approach for complexity.
  • Communication: Facilitates sharing and collaboration.
  • Savings: Reduces time and resource usage.


  • Complexity: Some algorithms can be intricate.
  • Not Universal: Not all problems have efficient algorithms.
  • Resource Intensive: High computing resources required.
  • Expertise Needed: Designing advanced algorithms demands skill.
  • Input Dependency: Performance varies with input.
  • Inflexibility: Might not adapt to dynamic changes.
  • Implementation Challenges: Converting algorithms to code can be complex.
  • Lack of Creativity: Might not accommodate creative solutions.
  • Learning Curve: Understanding complex algorithms can be demanding.



  • Graphical algorithm representation
  • Uses various shapes for different instructions (input, logic, processing, output, etc.)
  • Instructions written in boxes using English
  • Vital for programming, aiding understanding of complex problems
  • Helpful for visualizing logic in lengthy and intricate problems

Feature of Flowchart are:

  1. Visual representation
  2. Sequential steps
  3. Decision points
  4. Connectors and arrows
  5. Symbolic notations
  6. Easy-to-understand
  7. Process visualization
  8. Logic illustration
  9. Hierarchical structure
  10. Language-agnostic



  1. It provides a clear overview of the entire problem.
  2. It is easy to draw and understand.
  3. It is independent of any programming languages.
  4. It serves as a guide for program coding.


  1. It is time consuming work.
  2. It is difficult to translate flowchart into a program.
  3. It is difficult to later time modification.
  4. Some time it may be miscommunication.



  • ‘Pseudo’ means ‘fake’ or ‘false’
  • Pseudo code is like a “fake” code for planning before actual coding
  • It’s used after algorithm and flowchart creation
  • Resembles program code but might not be syntactically correct
  • Also referred to as ‘structured code’ or ‘structured English’
  • Helpful in planning and organizing program logic before actual coding


  • Clarity: Clear representation of program logic.
  • Language-agnostic: Not tied to a specific programming language.
  • Focus on Logic: Concentrates on problem-solving rather than syntax.
  • Planning: Enhances program structure planning.
  • Simplicity: Simplifies complex concepts.
  • Collaboration: Facilitates teamwork and discussion.
  • Time-Efficient: Reduces errors, saves coding time.
  • Debugging: Easier error spotting and correction.
  • Documentation: Serves as program design documentation.
  • Learning: Useful for teaching programming concepts.
  • Flexibility: Easily adaptable to changing requirements.


  • Ambiguity: Can be imprecise, leading to different interpretations.
  • Lack of Standards: No strict guidelines, causing confusion.
  • Syntax Ignored: Syntax errors might be overlooked.
  • Implementation Gap: Challenges translating into actual code.
  • Limited Detail: Might not capture all complexities.
  • Skill Required: Requires programming understanding.
  • Simplicity Trap: Oversimplification of complex problems.
  • Non-executable: Cannot be directly executed.
  • Validation Lacking: No syntax validation or testing.
  • Imagination Needed: Requires visualizing behavior for accuracy.


Control Structure: Sequence, Selection and Iteration

  • Programs have standard structures.
  • Programs consist of statements executed sequentially.
  • Power increases with controlled statement execution.
  • Execution can deviate from sequential order.
  • Repetition and conditions need control structures.
  • Control structures enable decision-making.
  • Control structures can be categorized as


  • Executes statements sequentially.
  • Order matters for successful execution.
  • Previous step before next step.


  • Based on condition, choose between paths.
  • True outcome: one action; false outcome: another.
  • Decision depends on a true or false condition.
  • Known as Branching statement


  • Iteration is known as looping and involves repeated execution of instructions until a condition is satisfied.
  • Loops have three components: initialization, condition, and counter.
  • Initialization sets the loop’s starting point, condition determines when it stops, and the counter tracks iterations.
  • Increment and decrement operators serve as counters.
  • Infinite loops occur if the condition is always true.
  • Three loop types: while, do while, and for loops.


Absolute binary, BCD, ASCIL, and Unicode (Code)

Absolute Binary:

  • Representation of data using fixed binary values.
  • Each bit directly represents a specific value.
  • No encoding or special meanings associated.



  • Represents decimal digits (0-9) using 4 binary digits.
  • Developed by IBM.
  • Converts each digit to its binary equivalent.
  • Allows coding of letters and special characters.
  • Advantage: No size limit; easy to add digits.
  • Contrast to binary format limits (8, 16, 32, 64 bits).
  • Fast conversion from decimal to binary.
  • Insufficient for business due to limited symbol representation (16, 24 symbols).



  • Originally a seven-bit code, later expanded to eight bits.
  • Developed for data transmission and processing.
  • IBM introduced ASCII-8 with 256 symbols.
  • Kept original 128 codes for compatibility.
  • Common in data communication and micro-computers.
  • Used for representing internal data.
  • Table represents ASCII codes for symbols.



  • Extended Binary Coded Decimal Interchange Code.
  • Character encoding standard used mainly on IBM mainframes.
  • Represents characters using 8-bit binary codes.
  • Predecessor to ASCII and Unicode.



  • Universal character encoding standard.
  • Represents characters in text, web pages, etc.
  • Supports all languages globally.
  • ASCII supports 128 characters, Unicode supports 1,000,000+.
  • Unicode uses up to 4 bytes per character.
  • UTF-8 and UTF-16 common encodings.
  • UTF-8 is efficient for English, others use more bytes.
  • Used for diverse character representation.


C Programming Language

 Introduction and Feature of C Language

  • Developed by Dennis Ritchie at Bell Labs (mid 1970s).
  • Initially for systems programming, but versatile.
  • Used in various applications from business to engineering.
  • Popular for personal computers due to small memory requirements.
  • First major use: UNIX operating system.
  • Linked with UNIX historically, but now independent.
  • Close to assembly language for efficiency.
  • Enables writing efficient code.
  • Can be challenging for certain application types.

Facts About C:

  • Created for UNIX OS development.
  • Successor of B language (early 1970s).
  • Formalized by ANSI in 1988.
  • Entire UNIX OS written in C.
  • Widely used for System Programming.
  • Many software and Linux OS use C.
  • MySQL RDBMS developed in C.

Feature of C:

  1. Easy learning due to the small command set.
  2. Follows structured programming.
  3. Provides machine independence.
  4. Supports modular programming.
  5. Acts as a bridge between high and low-level languages.
  6. Faster execution than other languages.
  7. Offers various data types and declarations.
  8. Includes numerous built-in functions.
  9. Powerful for commercial and hardware programming.
  10. Programs independent of CPU used.

Advantage of C: 

  1. Machine independent and portable.
  2. Considered the foundation of modern languages.
  3. Compiler widely accessible.
  4. Combines high-level and low-level capabilities.
  5. Known for fast execution.

Disadvantage of C:

  1. Lacks runtime checking.
  2. Challenging to fix errors in large programs.
  3. Doesn’t support object-oriented programming.
  4. Complexity may be difficult for beginners.

Structure of C program

  • Several building blocks known as function.
  • Function task independently.
  • Basic structure of C program: Preprocessor and Header Files, void main function(), Comments, Compiling Process.


Preprocessor and Header Files
  • Preprocessor:
      • Pre-compilation phase.
      • Processes directives starting with ‘#’.
      • Handles tasks like macro substitution and conditional compilation.
  • Header Files:
    • Contain declarations and sometimes definitions.
    • Modularize and organize code.
    • Included using ‘# include’ directive.
    • Commonly have ‘.h’ extensions.


Void main function ()
  • Contain main () function.
  • Written inside the scope {}.
  • Actual program code are written in the executable part


  • Comment are not internal part of program code.
  • Writing comments helps to understand the flow of program.
  • Practice for internal documentation of programmer.
  • Use for further modification and program testing.


Compiling Process
  • Process of converting source file into executable files.
  • Automatically performed by the C compiler.


C Preprocessor and Header Files

  • Header files, standard library file of C programming language.
  • Detailed information about variables, constant, operators, etc.
  • Files included program code before compilation.
  • Preprocessor directives, include or link of header files to program codes
  • List of header files are:
    • #include<stdio.h>
    • #include<conio.h>
    • #include<math.h>
    • #include<string.h >


Character Set used in C

  • Define a group of letters, words, numbers, symbols, expressions used in C language.
  • Some of them are:
    • Letters: uppercase A to Z and lowercase a to z.
    • Digits: 0 to 9
    • Special Characters: listed in the table.

Special Characters:

 Use of Comments

  • Arbitrary text between /* and */.
  • Enhance readability and understanding.
  • Explain the program’s purpose.
  • Not executable; ignored by compiler.
  • Can be inserted almost anywhere except in constants.
  • Aid in documentation, debugging, and testing.
  • No impact on execution speed or program size.
  • Helpful for programmers and users.
  • Good practice for program clarity.
  • Written in two form:
    1. //Single Line Comments
    2. /*Multi-Line………………………..comments*/


Identifiers, Keywords and Tokens

  • Smallest part is called C tokens.
  • Written by using these tokens 
  • Types of C tokens are:


  • Reserved by the C compiler
  • Known as Keywords
  • Identifiers in the program.


  • Name given to program units like: variables, structure, function, etc.
  • Not define in programmer language
  • But define by programmer
  • Some rules are:
    1. Must start with an alphabet or underscore.
    2. Can consist of letters, digits, and underscore.
    3. Cannot be a standard C keyword.
    4. No spaces are allowed.
    5. Both uppercase and lowercase characters are valid.

Valid Identifiers

A1        B34        FIRST_NAME         x_1


Invalid Identifiers

1A        34AB        int       void        First-NAME        X.1


Basic Data Types in C

  • Form of number, character, string or record are known as data types.
  • Provide two data types: Primary data types and Secondary data types.


Primary Data Types:

  • Known as fundamental data types
  • Used to build other data types


Constants and Variables


  • Variables are named memory locations to store values of the same datatype.
  • They are storage containers for values during program execution.
  • Variables are declared before being used.
  • Each variable must have a specified datatype.
  • Data Type determines value range, type, and memory size.
  • Rules of choosing variables name:
      1. Can include uppercase and lowercase letters (A-Z, a-z).
      2. Can include digits (0-9) and underscore (_).
      3. Must start with a letter or underscore.
      4. Blank spaces are not allowed.
      5. Special characters like # and $ are not allowed.
      6. C keywords cannot be used as variable names.
      7. Variable names are case-sensitive.
      8. Values can be numeric or alphabetic.
      9. Variable types can be char, int, float, double, or void.
  • Two main variable types:

Numeric Variable:

      • Stored only numeric data
      • Maybe a whole number or a fractional number.
      • Example: integer, floating point, double

String Variable:

      • Stored only character data 
      • May be single character or string
      • Example: table of string, character, array of character(string)



    • Value don’t change during execution of program.
    • Has several types of constant.
    • Types of constant are:
  1. Integer Constant
      • Sequence of digits
      • Decimal integer, octal integer, hexadecimal are types
      • Example:

Decimal Integer          123       -31      0      +78

Octal Integer                 O26       O      O347     O676

Hexadecimal Integer OX2     OX8C        OXbcd        OX


2. Character Constant

      • Stores only character
      • Enclosed by single quotation mark
      • Example:

                                   ‘A’          ‘B’          ‘h’          ‘2’          ‘6’


3. String Constant

      • Set of character enclosed by double quotation mark
      • May be alphabet, number, special character and blank space.
      • Example:

                                    “VISHAL”          “1234”          “God Bless”          “!…?”


4. Symbolic Constant

      • Substitute the value or expression to the constant name.
      • Using the pre-processor #define.
      • Example:

                                       #define PI 3.14

                                      #define name “HSEB”

                                     #define area 100

5. Escape Sequence Constant

    • Non-printing character starts with slash(\)
    • Special character used in output function
    • Table and meaning of escape sequence are:


Difference between Variable and  Constant 

Variable Constant
Holds a value that can be modified during program execution. Holds a fixed value that cannot be changed during program execution.
Declared using a data type and an identifier (name). Declared using the const keyword.
Values can be assigned and reassigned as needed. Values must be assigned at the time of declaration.
Used to store and manipulate changing data. Used to represent unchanging data.


Types of Specifier

  • Known as format specifier.
  • Types and format of value to be print or entered.
  • Begins with % and ends with conversion character.
  • Datatypes of the corresponding argument.


 Simple and Compound Statements

  • Terminated by semicolon.
  • Cause the computer to carry out some action.

Simple Statement:

  • An expression followed by a semicolon.
  • Causes the expression to be evaluated.

Compound Statement:

  • Several individual statements enclosed in a pair of braces { }.
  • Capability for embedding statements within other statements


Operators and Expressions

  • Symbols carry out specific calculations or logical comparison.
  • Variable or constant that holds data operation.
  • Combination of operators and operands.
  • Wide variety of operators

Arithmetic Operators:

  • Perform simple arithmetic calculations like:  additions, subtraction, multiplication, etc
  • Uses two operands so that it is called binary operator
  • Types of arithmetic operators are:


Relational Operators:

  • Compare two expressions.
  • Bring out the decision accordingly
  • Known as Comparison operator

Logical Operators:

  • Used to give logical value i.e. true or false
  • Compare or evaluate logical and relational expressions

Assignment Operators:

  • Assign the value of expression into a variable.
  • Written form: variable = expression


Unary Operators:

  • Increment and Decrement operators are useful.
  • Extensively used in loops
  • Syntax of Operators are:
    • ++variable name (increment prefix)
    • variable name ++ (increment prefix)
    • – -variable name (decrement prefix)
    • variable name – – (decrement prefix)


Ternary Operator (? : operator):

  • Known as conditional operator 
  • Check the conditional to make a decision.
  • Uses two symbol : (?) and (:)


The Comma Operator:

  • Used to link related expressions together.
  • Evaluated left to right and expression value of right



  • Expressions combine variables, constants, and operators.
  • Each expression evaluates to a value with a specific data type.
  • Operators perform operations on operands within expressions.
  • Type promotion and conversion ensure compatibility.
  • Order of evaluation and side effects are important considerations.
  • Expressions can be assigned to variables using the assignment operator.
  • Parentheses control the order of evaluation.
  • Function calls can be considered expressions if they return values.

Type Casting and Conversions

Implicit Type Conversion:

  • Mixing of constants and variable of different types in expression
  • Automatically converts any intermediate values to proper types.
  • Evaluates without losing any significance


Explicit Type Conversion:

  • Forcing type conversion differently from automatic.
  • Called explicit conversion or casting.
  • Used to change data types deliberately.


Introduction to Library Functions

  • Function that pre-defined in programming language
  • Used for input/output operations
  • Function can perform specific tasks and return specific values.


 Input/output (I/O) Functions

  • Provided by C compiler or C library.
  • Collectively called Standard I/O Library functions.
  • Used for input and output operations.
  • Embedded in the stdio.h header file.
  • Two main categories: Input and Output functions.

Other Input/Output Functions

  • ‘getchar()’: Reads a single character.
  • ‘putchar()’: Displays a character.
  • Operate on individual characters.
  • Used for character input/output


Selection Control Statement: Decisions (if, if-else, if-else-if, nested and switch)

Introduction to Control Statement
  • Program execution is typically sequential, line by line.
  • Not suitable for all scenarios, like making decisions.
  • Decision-making statements verify conditions.
  • Determine whether a block of code is executed.
  • Used to solve problems where choices are needed.


Branching Statement
  • Selection is made based on condition.
  • Option to go when the given condition is true or false
  • Totally directed by the result obtained from checking condition.
  • Using selective control structure are called conditional statement
  • Types of control used for decision making
  • Two Categories are: Conditional Branching statement, switch-case statement
  • Program executive based on the condition checked
  • Used in different forms are:
    • If statement
    • If else statement
    • If else if statement
    • Nested if else statement

If statement:

  • Verifies a given condition.
  • Executes a block of statements if the condition is true.
  • Skips the block if the condition is false.

If else statement:

  • Verifies a given condition.
  • Executes one of two blocks based on condition.
  • If the condition is true, execute the true block.
  • If the condition is false, execute the false block.

If else if statement:

  • Used when multiple conditions need to be evaluated.
  • Handles more than two possible actions.
  • Provides a sequence of condition checks.
  • Each condition is followed by a corresponding action.
  • Only the action corresponding to the first true condition is executed.

nested if else statement:

  • If statement inside another if statement.
  • Referred to as a “nested if.”
  • Helps create hierarchical conditions.
  • Increases complexity for more intricate logic.

Switch case Statement:

  • Suitable for selecting one option from many.
  • Solves problems with multiple options efficiently.
  • Simpler alternative to nested if statements.
  • Compares a given value with values associated with options.
  • Execution starts from the matched option (case).

Iteration Control Statement: Looping (while, do while, for nested)

  • Repeatedly executing a set of instructions.
  • Controlled by a specific number or condition.
  • Part of control statements in C.
  • Iteration statements are also called loops.
  • Loops enable repetition in C programming.
  • Types of looping are:

while loop:

  • Repeats a statement or block while a condition is true.
  • Executes as long as the condition remains true.
  • Also known as “Entry control” looping statement.
  • Rules of while loop are: 
    • Use the keyword “while” in lowercase.
    • If the condition involves a variable, assign a value before using it.
    • Modify the variable value within the ‘while’ block as needed.
    • The condition can be a direct integer value, variable, or a condition.


do while loop:

  • Repeats a statement or block while a condition is true.
  • Executes at least once before checking the condition.
  • Also known as “Exit control” looping statement.


Difference between while loop and do while loop
while loop  do while loop
Condition is checked before entering the loop Condition is checked after executing the loop body.
If the condition is false initially, the loop might not execute at all. The loop body always executes at least once, even if the condition is false.
Execution might not enter the loop body if the condition is false from the beginning. Execution enters the loop body before the condition is checked.


for loop:

  • Pre-tested loop for a known number of iterations.
  • Consists of three parts: initialization, condition, and update.
  • Control variable is initialized first.
  • Condition is tested, and the loop continues if true.
  • If the condition is false, the loop terminates.
  • Statements in the loop body are executed.
  • Control variable is updated and the condition re-evaluated.
  • Loop continues until the condition becomes false.


Nested Loop:

  • Nested loop: loop within a loop.
  • Outer loop triggers the inner loop.
  • Inner loop executes completely.
  • Outer loop triggers inner loop for each iteration.
  • Process repeats until the outer loop finishes.


Infinite Loop:

  • Repeats program statements endlessly.
  • Lacks a termination condition.


Jumping Statement
  • Used to control program flow.
  • Execute or skip program statements.
  • Three types: break, continue, and goto.

break Statement:

  • Terminates ‘switch’ case statements.
  • Terminates looping statements: ‘while’, ‘do-while’, and ‘for’.


continue Statement:

  • Used inside loops.
  • Jumps to the loop’s beginning for the next iteration.
  • Skips the execution of statements within the loop for the current iteration.


goto Statement:

  • Used to jump between lines in a program.
  • Enables jumping top-to-bottom or bottom-to-top.
  • Requires a label as the target destination.
  • Label is a name for an instruction or line.
  • Execution control jumps directly to the labelled line.


Array: definition, types (1D and 2D), matrix addition and subtraction

Introduction to Array
  • Used for managing large numbers of similar data values.
  • Provides a single variable to store multiple values of the same type.
  • Offers easier handling and organization of data.
  • Stores values in continuous memory locations.
  • Enhances efficiency in accessing and managing data.
Characteristics of Array:
  • Collection of elements of the same data type.
  • Elements stored in contiguous memory locations.
  • Accessed using an index or position.
  • Fixed size determined during declaration.
  • Elements can be accessed and manipulated efficiently.
  • Can be used to represent lists, tables, matrices, etc.
Advantages of Array:
  1. Random Access: Elements can be accessed directly using array indices.
  2. Code Efficiency: Requires fewer lines of code for multiple elements.
  3. Simplified Access: Provides easy access to all elements.
  4. Efficient Traversal: Can be traversed easily using a single loop.
  5. Simplified Sorting: Sorting is easier with fewer lines of code.
Disadvantage of Array:
  1. Fixed Size: Array size is determined during declaration and cannot be changed.
  2. Limited Dynamic Behavior: Unlike linked lists, arrays are not dynamic in nature.
  3. Costly Insertion and Deletion: Inserting and deleting elements can be inefficient due to memory reallocation and shifting.
  4. Memory Management: Array elements need to be managed explicitly with new memory allocation.
  5. Static Structure: Array structure is static, making it less flexible for changing data requirements.


Types of Arrays
  • Arrays are classified into two types.
    • Single Dimensional Array / One Dimensional Array
    • Multi Dimensional Array


One Dimensional Array:

  • Used to store a list of values of the same data type.
  • Store data in a linear, sequential form.
  • Often referred to as one-dimensional arrays or linear arrays.
  • Suitable for representing a row of values.

Array Initialization

  • Arrays can be initialized during declaration using curly braces {}.
  • Use commas to separate the initialization values within the curly braces.
  • Partial initialization is allowed; remaining elements will be set to zero.
  • For complete initialization, the array’s dimension is not needed; the compiler will adjust it based on the provided data.


Multi Dimensional Array:

  • Multi-dimensional arrays consist of arrays within arrays.
  • They have more than one dimension or size.
  • Examples include two-dimensional, three-dimensional, and higher-dimensional arrays.
  • Two-dimensional arrays are commonly used to store tabular data and matrices.


String: Definition and String Function: strlen(), strcat(), strcamp(), strrev(), strcpy(), strlwr(), strupr()

Introduction to string
  • Strings are sets of characters enclosed in double quotes.
  • Strings are created using one-dimensional arrays of the character data type.
  • Strings are terminated with a NULL character (‘\0’).
  • The C compiler automatically appends a NULL character at the end of a string.
  • Strings in C are represented as character arrays of a single dimension.


String Handling Functions
  • Pre-defined functions for working with string values.
  • Defined in the string.h header file.
  • Need to include string.h before using these functions.
  • Example:
    • strrev() function
    • strcpy() function
    • strcat() function
    • strcmp() function


Array of Strings:

  • Array of strings is a dimensional array of characters.
  • Also called a table of strings.
  • Useful for sorting string-related problems.
  • Can be treated like a two-dimensional array.