📘 Topic: Syntax-Directed Translation and Syntax-Directed Translation Schemes

What is Syntax-Directed Translation (SDT)?

5 Key Points about SDT

• 💡 Each production rule in grammar is linked with semantic actions (code or instructions).
• 💡 Translation happens during parsing using these actions.
• 💡 Helps generate intermediate code or target code from source code.
• 💡 It ties syntax (grammar) with translation steps.
• 💡 Used in compiler’s syntax-directed translation phase.

What is Syntax-Directed Translation Scheme (SDTS)?

Components of SDTS

• Grammar (CFG) rules
• Semantic rules or actions (attached to grammar rules)
• Attributes (values computed during parsing)

Example of SDTS

E → E + T { E.val = E.val + T.val }
E → T { E.val = T.val }
T → id { T.val = lookup(id) }
                

Types of Attributes

• Synthesized Attributes: Computed from child nodes up to parent node.
• Inherited Attributes: Computed from parent or sibling nodes down to child nodes.

Summary in Hinglish

• SDT me hum grammar ke rules ke sath translation instructions attach karte hain.
• SDTS ek aisa grammar hota hai jisme semantic actions bhi hoti hain.
• Ye compiler me source code ko intermediate ya target code me translate karne me help karta hai.
• Attributes ke through values ya properties compute hote hain.

Suggested Diagram

Grammar Rules + Semantic Actions → Syntax-Directed Translation Scheme (SDTS)  
↓  
Parsing + Action Execution → Translation of Source Code  
↓  
Intermediate/Target Code Generation
            

📘 Topic: Intermediate Code

Definition of Intermediate Code

5 Important Points about Intermediate Code

• 💡 Intermediate code is machine-independent — it is not tied to any specific hardware.
• 💡 It acts as a bridge between source code and machine code.
• 💡 Facilitates optimization of code before final translation.
• 💡 Helps make compilers portable across different machines.
• 💡 Commonly used intermediate representations include three-address code, syntax trees, and postfix notation.

Why use Intermediate Code?

• Direct translation from source code to machine code is complex.
• Intermediate code allows compilers to separate front-end and back-end parts.
• Makes optimization easier and more effective.
• Helps in supporting multiple target machines using the same front-end.

Types of Intermediate Code

Example of Three-Address Code

t1 = c * d
t2 = b + t1
a = t2
                

Advantages of Intermediate Code

• 👍 Simplifies machine code generation.
• 👍 Easier to perform optimizations like dead code elimination, constant folding.
• 👍 Makes compiler modular (front-end, middle-end, back-end).
• 👍 Improves portability of compilers.
• 👍 Facilitates code analysis.

Disadvantages of Intermediate Code

• 👎 Requires extra memory to store intermediate code.
• 👎 Additional step may increase compilation time slightly.
• 👎 Needs design of intermediate representation carefully.

Summary in Hinglish

• Intermediate code source code aur machine code ke beech ka code hota hai.
• Yeh machine independent hota hai aur compiler ko optimize karne mein help karta hai.
• Three-address code sabse popular intermediate representation hai.
• Intermediate code compiler ko modular aur efficient banata hai.

Suggested Diagram

Source Code
    ↓
Syntax Analysis
    ↓
Intermediate Code Generation
    ↓
Optimization
    ↓
Machine Code Generation
            

📘 Topic: Postfix Notation (Reverse Polish Notation)

Definition of Postfix Notation

How is Postfix different from Infix?

5 Important Points about Postfix Notation

• 💡 No need for parentheses to specify order of operations.
• 💡 Easier for computers to evaluate expressions.
• 💡 Evaluation can be done using stack data structure.
• 💡 Commonly used in compilers and calculators.
• 💡 Helps in generating intermediate code.

Example: Infix to Postfix Conversion

Step-by-step Evaluation of Postfix Expression

Advantages of Postfix Notation

• 👍 No need to remember operator precedence rules.
• 👍 Easier and faster to evaluate by machines.
• 👍 Simple algorithm using stacks for evaluation.
• 👍 Eliminates ambiguity in expressions.

Disadvantages of Postfix Notation

• 👎 Not easy for humans to read or write compared to infix.
• 👎 Needs conversion from infix before evaluation in many cases.

Summary in Hinglish

• Postfix notation me operator operands ke baad likha jata hai.
• Isme parentheses ki zarurat nahi hoti.
• Yeh computer ke liye expressions ko evaluate karna aasaan banata hai.
• Stack ka use karke postfix expression ko asaani se calculate kar sakte hain.

Suggested Diagram

Infix Expression:   (A + B) * C
       ↓ Conversion
Postfix Expression: A B + C *
       ↓ Evaluation (using stack)
            

📘 Topic: Parse Trees and Syntax Trees

What is a Parse Tree?

What is a Syntax Tree?

5 Important Points about Parse Trees

• 💡 Shows complete derivation according to grammar.
• 💡 Includes all terminals and non-terminals.
• 💡 Root node is the start symbol of the grammar.
• 💡 Leaves represent terminals (actual tokens).
• 💡 Helps in verifying syntax correctness.

5 Important Points about Syntax Trees

• 💡 Focuses on semantic structure, not full grammar details.
• 💡 Leaves are operands (like variables or constants).
• 💡 Internal nodes are operators or constructs.
• 💡 Smaller and easier to use for further processing (like code generation).
• 💡 Removes redundant nodes (like parentheses or intermediate non-terminals).

Example: Parse Tree vs. Syntax Tree for an Expression

Difference Between Parse Tree and Syntax Tree

Summary in Hinglish

• Parse Tree pura grammar ka structure dikhata hai, saare symbols ke sath.
• Syntax Tree sirf zaroori cheezein rakhta hai, simple aur chhota hota hai.
• Syntax Tree ko compiler aage code generation ke liye use karta hai.
• Parse Tree se hum confirm karte hain ki input grammar ke rules ko follow karta hai.

Suggested Diagram

Parse Tree: (Detailed with all grammar symbols)
          E
         /|\
        ( E + T )
       /      \
      a        b

Syntax Tree: (Simplified)
          *
         / \
        +   c
       / \
      a   b
            

📘 Topic: Three Address Code (TAC)

Definition of Three Address Code

5 Important Points about Three Address Code

• 💡 Each statement has one operator and up to two operands plus a result.
• 💡 Operands can be variables, constants, or temporary variables.
• 💡 Easy to generate from expressions and simple to optimize.
• 💡 Helps separate compiler phases (front-end and back-end).
• 💡 Commonly used in the form: x = y op z or x = op y or goto label.

Formats of Three Address Code

• Assignment: x = y
• Binary operation: x = y + z
• Unary operation: x = -y
• Copy: x = y
• Goto statement: goto L
• Conditional jump: if x < y goto L
• Parameter passing: param x
• Function call: call p, n (p is procedure, n is number of arguments)
• Return statement: return x

Example: TAC for an Expression

t1 = c * d
t2 = b + t1
a = t2
                

Advantages of Three Address Code

• 👍 Simple to generate and understand.
• 👍 Easy to optimize and translate to machine code.
• 👍 Facilitates code analysis and transformations.
• 👍 Modular and portable intermediate representation.
• 👍 Makes complex expressions easier to break down.

Disadvantages of Three Address Code

• 👎 Can produce many temporary variables, increasing memory use.
• 👎 More instructions compared to high-level code.
• 👎 May require extra steps for optimization to reduce temporaries.

Summary in Hinglish

• Three Address Code mein instructions teen operands tak hote hain.
• Yeh intermediate code hai jo compiler ko source code se machine code mein badalne mein madad karta hai.
• Isme temporary variables use karke complex expressions ko chhote steps mein todte hain.
• Code optimize karna aur translate karna easy hota hai.

Suggested Diagram / Flow

Expression: a = b + c * d

    c    d
     \  /
     multiply (t1 = c * d)
        |
      b  t1
       \ /
       add (t2 = b + t1)
         |
         a = t2
            

📘 Topic: Quadruples and Triples in Intermediate Code

What are Quadruples?

Example of Quadruple

What are Triples?

Example of Triples

Comparison between Quadruples and Triples

Advantages

• Quadruples:
  • 👍 Easy to understand and manipulate.
  • 👍 Result is explicitly available.
  • 👍 Good for code generation and optimization.
• Triples:
  • 👍 Requires less memory (no result field).
  • 👍 Compact representation.

Disadvantages

• Quadruples:
  • 👎 Uses more space due to result field.
• Triples:
  • 👎 More complex to handle result references during optimization.
  • 👎 Modifying code is harder because results are positional.

Summary in Hinglish

• Quadruples mein har instruction ke 4 parts hote hain, jisme result bhi clearly hota hai.
• Triples mein result ka field nahi hota, result ko instruction number se refer karte hain.
• Quadruples zyada flexible aur asaani se modify kar sakte hain, par space zyada leta hai.
• Triples space bachate hain, par thoda handling complex hota hai.

Suggested Diagram

Expression: a = b + c * d

Quadruples:
[ *, c, d, t1 ]
[ +, b, t1, t2 ]
[ =, t2, -, a ]

Triples:
0: [ *, c, d ]
1: [ +, b, (0) ]
2: [ =, (1), - ]
            

📘 Topic: Translation of Simple Statements and Control Flow Statements

What is Translation in Compiler?

Translation of Simple Statements

Example: Simple Statement Translation

t1 = c * d
t2 = b + t1
a = t2
                

Translation of Control Flow Statements

Example: if statement Translation

if (a < b) 
    c = a;
else
    c = b;
                

if a < b goto L1
goto L2
L1: c = a
goto L3
L2: c = b
L3:
                

Example: while loop Translation

while (a < b) {
    a = a + 1;
}
                

L1: if a >= b goto L2
a = a + 1
goto L1
L2:
                

Important Points about Control Flow Translation

• 💡 Labels are used to mark places in code to jump to.
• 💡 goto is used for unconditional jump.
• 💡 Conditional jump uses if statements to decide the flow.
• 💡 Translation breaks complex control flow into simple jump instructions.
• 💡 Helps compiler manage program flow in machine or intermediate code.

Summary in Hinglish

• Simple statements jaise assignment ko temporary variables ke sath tod kar translate karte hain.
• Control flow jaise if, while ko labels aur jump instructions ke through translate karte hain.
• Labels aur goto se program ka flow control hota hai.
• Yeh intermediate code machine ke liye asaani se samajhna possible banata hai.

Suggested Diagram

if (a < b) {
    c = a;
} else {
    c = b;
}

Translation:

if a < b goto L1
goto L2
L1: c = a
goto L3
L2: c = b
L3:
            

📘 Topic: Type Checking

What is Type Checking?

Why Type Checking is Important?

• 💡 Prevents errors like adding number to string.
• 💡 Ensures program behaves correctly.
• 💡 Helps catch bugs during compilation, not at runtime.
• 💡 Improves program reliability and safety.
• 💡 Helps the compiler generate correct code.

Examples of Type Checking

Types of Type Checking

• 1. Static Type Checking
  • Done at compile time.
  • Detects errors before running the program.
  • Languages: C, Java, C++.
• 2. Dynamic Type Checking
  • Done at runtime (while program is running).
  • Errors detected when that line executes.
  • Languages: Python, JavaScript.

Type Checking Techniques

• Type Inference: Compiler automatically figures out the type (like in modern languages).
• Type Conversion: Compiler changes one type to another if needed (like int to float).
• Type Compatibility: Checks if types can be combined or assigned.

Key Points about Type Checking

• 💡 Type checking ensures expressions and assignments are type-safe.
• 💡 Helps prevent crashes and unexpected behavior.
• 💡 Static checking is faster but less flexible.
• 💡 Dynamic checking is flexible but can cause runtime errors.

Summary in Hinglish

• Type checking compiler ka process hai jisme check karte hain ki variable ka data type sahi hai ya nahi.
• Static type checking compile time mein hota hai aur errors ko pehle hi pakad leta hai.
• Dynamic type checking runtime mein hota hai aur errors tab pakadta hai jab wo code chalta hai.
• Yeh programming errors ko kam karta hai aur program ko safe banata hai.

📘 Topic: Type Conversions

What is Type Conversion?

Why Type Conversion is Needed?

• 💡 To perform operations between different types (like int + float).
• 💡 To avoid type errors during compilation or execution.
• 💡 To allow mixed-type expressions in programming.
• 💡 To ensure correct storage and representation of data.
• 💡 To follow language or system rules about type usage.

Types of Type Conversions

• 1. Implicit Type Conversion (Type Coercion)
  • Automatically done by the compiler or interpreter.
  • Programmer doesn’t need to write conversion code.
  • Example: Adding int and float — int is automatically converted to float.
• 2. Explicit Type Conversion (Type Casting)
  • Programmer manually converts one type to another.
  • Done using casting operators or functions.
  • Example: (float) 5 converts integer 5 to float 5.0.

Examples of Type Conversions

int a = 5;
float b = 3.2;
float c = a + b;  // a is converted to float automatically
                

float x = 7.8;
int y = (int) x;  // x is explicitly converted to int (7)
                

Common Conversions

• int → float
• float → int (may lose decimal part)
• char → int (ASCII value)
• int → char (character representation)
• string → int/float (using functions like atoi or stof)

Important Points about Type Conversions

• 💡 Implicit conversion is safe but can sometimes cause unexpected results.
• 💡 Explicit conversion gives programmer control but may cause data loss.
• 💡 Some conversions are not allowed or need special handling (like converting string to int).
• 💡 Conversions affect how data is stored and used in memory.

Summary in Hinglish

• Type conversion ek process hai jisme ek data type ko doosre mein badalte hain.
• Implicit conversion automatically hota hai compiler ke dwara.
• Explicit conversion programmer khud karta hai casting ke through.
• Kabhi-kabhi conversion mein data loss bhi ho sakta hai, jaise float ko int mein convert karne par decimal hat jaata hai.

📘 Topic: Equivalence of Type Expressions

What is Equivalence of Type Expressions?

Why is it Important?

• 💡 To verify if two variables or expressions have compatible types.
• 💡 Helps compiler decide if operations or assignments are valid.
• 💡 Ensures safety and correctness of programs.
• 💡 Avoids errors when types look different but actually mean the same.

Example of Type Equivalence

Type1 = struct { int x; float y; }
Type2 = struct { int x; float y; }
                

Types of Equivalence

• 1. Name Equivalence
  • Two types are equivalent if they have the same name.
  • Even if structure is same, different names mean not equivalent.
  • Example:

    
    type A = struct { int x; }
    type B = struct { int x; }
                                

    A and B are NOT equivalent by name equivalence.

• 2. Structural Equivalence
  • Two types are equivalent if their structure is identical.
  • Names don’t matter, only the content and layout matter.
  • Example:

    
    struct { int x; int y; }
    struct { int x; int y; }
                                

    Equivalent by structure even if unnamed.

Important Points about Equivalence

• 💡 Name equivalence is simple but restrictive.
• 💡 Structural equivalence is flexible but can be complex to check.
• 💡 Some languages prefer one type equivalence method over another.
• 💡 Equivalence is crucial during assignments, parameter passing, and type checking.

Summary in Hinglish

• Type expressions ki equivalence check karte hain ki do types same hain ya nahi.
• Name equivalence mein sirf naam count karta hai.
• Structural equivalence mein structure (fields, order) check karte hain.
• Yeh check karna compiler ke liye important hota hai taaki sahi program likha ja sake.

📘 Topic: Overloading of Functions and Operations

What is Overloading?

Why is Overloading Used?

• 💡 To make code simpler and readable.
• 💡 Same name can be used for similar operations on different data types.
• 💡 Helps in creating flexible and reusable code.
• 💡 Avoids confusion by keeping consistent names.
• 💡 Allows different behavior with same function/operator name.

Types of Overloading

• 1. Function Overloading
  • Multiple functions with the same name but different parameters (number or type).
  • Compiler decides which function to call based on arguments.
  • Example:

    
    int add(int a, int b) { return a + b; }
    float add(float a, float b) { return a + b; }
                                

• 2. Operator Overloading
  • Giving new meaning to operators like +, -, *, etc. for user-defined types (like classes).
  • Example: For a class Complex, overloading + to add two complex numbers.

Examples of Overloading in Action

void print(int x) { cout << x; }
void print(string s) { cout << s; }
print(5);       // calls print(int)
print("Hi");    // calls print(string)
                

class Complex {
  float real, imag;
public:
  Complex operator+(const Complex& c) {
    return Complex(real + c.real, imag + c.imag);
  }
};
                

Important Points about Overloading

• 💡 Overloading increases program readability.
• 💡 Overloaded functions must differ in parameter list.
• 💡 Return type alone is not enough for overloading.
• 💡 Operator overloading allows customizing operations for objects.
• 💡 Not all operators can be overloaded (e.g., . operator in C++).

Summary in Hinglish

• Overloading ka matlab hai ek naam ke functions ya operators ko alag-alag tareeke se use karna.
• Function overloading mein same naam ke functions alag parameters ke saath hote hain.
• Operator overloading mein hum operators ka meaning change kar sakte hain user-defined types ke liye.
• Isse code clean, readable aur flexible hota hai.